Abdulhadi, R., K. Kartawinata and S. Sukardjo. 1981. Effects of mechanized logging in the lowland dipterocarp forest at Lempake, East Kalimantan. Malaysian Forester 44(2-3): 407-418.
· 11 trees/ha were removed, with stump diameters ranging
from 80 to 150 cm.
· 41% of the residual stand suffered branch and crown
damage, while 59% was undamaged.
· The damaged trees were, for the most part, located close to tractor paths, skid trails and felled trees.
Agom, D.I. 1994. Report of study on methodology and productivity of stump site chain saw timber operators. Forestry Dept., Cross River State, Nigeria, Working Paper No. 2. 24pp.
· The average log conversion rate at the stump was
36.2%, with a maximum of 54% recorded.
· A large amount of useful wood was
left in the forest because of the adherence of the dealers and buyers to specific flitch dimensions.
Agom, D.I. and D. Ogar. 1994. Report of study on timber extraction in the Ikobi concession area in Afi River forest reserve. Forestry Dept., Cross River State, Nigeria, Working Paper No. 3. 15pp.
· Extraction in the concession was heavily mechanized
and productive, but caused considerable disturbance to the surrounding
areas
· There was recorded to be 12.2% waste
Agyeman, V.K., C. Turnbull and M.D. Swaine. 1995a. Maintenance of biodiversity in the tropical high forest: current research initiatives in Ghana. IUFRO XX World Congress, Proceedings, Abstract. p.76-77.
· Harvesting more than 3.5 m2/ha of basal area will exceed the forest's ability
to regenerate.
· Gap sizes have an influence.
Agyeman, V.K., C. Turnbull and M.D. Swaine. 1995b. Maintenance of biodiversity in the tropical high forest: effects of selective logging. IUFRO XX World Congress, Proceedings.
· Gap opening per tree felled ranged from 350-1800 m2.
· Felling 2.6 trees/ha in the Bura Forest
Reserve in Ghana resulted in 13% logging disturbance.
· Canopy gaps account
for 50% of the disturbance, skid trails 38% and haul roads 12%.
Ahluwalia, S.S. and S. Karnasudirdja. 1995. Notes on lesser-used species in Malaysia and Indonesia. ITTO, Tropical Forest Update 5(2): 10.
· Logging intensity in Malaysia has increased from an average of 24 m3/ha (1971-78) to 45 m3/ha (1979-90).
Ahmad, S., Brodie, J.D., & Sessions, J. 1999. Analysis of two alternative harvesting systems in peninsular Malaysia: Sensitivity analysis of costs, logging damage and buffers. Journal of Tropical Forest Science 11(4): 809-821.
· The study was carried out in hill dipterocarp forest
in eastern Peninsular Malaysia.
· Selective Management System with rotation
length of 30 years.
· Cutting limit 45-50cm dbh.
· New system incorporates
directional felling and improved road construction.
· Skidding efficiency has
improved under the new system.
· Comparison of logging costs (cost reduction of 4%):
Activity |
New System (US$/m3) |
Traditional System (US$/m3) |
Felling and cross-cutting |
1.26 |
1.63 |
Skidding |
2.88 |
2.90 |
Loading and unloading |
0.66 |
0.25 |
Short hauling |
2.29 |
2.79 |
Supporting costs |
6.31 |
6.35 |
Total logging costs |
13.39 |
13.92 |
· Under the new system 30% of the total volume was damaged during harvesting. With a discount rate of 4%, the damage equals 61.92 US$/m3.
· Under the traditional system it is assumed that 40% of the total volume are damaged during harvesting. With a discount rate of 4%, the damage equals 85.88 US$/m3.
Ahrenholz, T. 1991. Die Erschliessungssituation bei der Nutzung tropischer immergruener Feuchtwaelder in Ostkalimantan; Indonesien- eine Fallstudie an einem Beispielsbetrieb. Diploma thesis. University of Goettingen. 1991. 123pp.
· This study was carried out in eastern Kalimantan,
Indonesia.
· The commercial volume of primary forests in this region is 101.9 m3/ha for trees >20cm dbh.
· In plantation forests, 200m3/ha of commercial timber could be
produced on a 12-year rotation.
· The following cutting cycles are proposed:
saw logs 20-30 years, pulpwood 8-20 years, fuelwood 5 years.
· Two harvesting
systems were evaluated: the TPI system (Indonesian Selection System) and the HTI
system (clearfelling and artificial regeneration).
· Directional felling is
not possible with the equipment currently available.
· The following data
were found for stem volume and log waste (Radtke, 1990):
Stem volume (dbh >15cm) (m3/ha) |
Volume utilized (m3/ha) |
Log waste (m3/ha) | |
Trees felled |
128.8 |
76.2 |
52.6 |
Felling damage |
23.8 |
- |
23.8 |
Total |
152.6 |
76.2 |
76.4 |
· On the study site, the volume extracted was equal to
the volume damaged or left behind.
· On average, 10 harvestable trees were found per hectare (79.40 m3/ha).
· The
average road density was 18.34 m/ha (3.25m of primary roads per hectare); the
average skidding distance was 163.4m.
· Between 25 and 48% of the skid trails
were traversed 4 to 8 times during harvesting operations.
· The average
skidding costs were US$ 2.2 to 2.5 per cubic metre.
· In the study area, 5.4%
of the area was affected by roads (primary roads 1.6%, secondary roads with
water bound surface 0.5%, temporary secondary roads 3.2%).
· On average, 20.7% of the area was affected by skidding (26.8 m2 were affected per cubic metre of timber
extracted).
· According to RADTKE 1990, 14% of the area was covered with logging debris after felling.
Andel, S. 1978. The impact of harvesting systems on tropical forest management in South East Asia. Food and Agriculture Organization of the United Nations, Final Report MAL/75/012.
· Proper logging in West Malaysia may add M$51-70/ha, whereas post logging silvicultural treatments (including planting of roads and landings) may cost about M$200/ha.
Andrewartha, R. 1998. Reduced-impact logging developments in Sabah. ITTO Tropical Forest Update 8(1): 24-26.
· No blading-off of soil on skid tracks less than 15º sideslope.
Appanah, S. and F.E. Putz. 1984. Climber abundance in virgin dipterocarp forest and the effect of pre-felling climber cutting on logging damage. Malaysian Forester 47(4): 335-342.
· 13 ha study area had 376 climbers/ha >2 cm
dbh.
· Cutting climbers before logging reduced the number of trees pulled
down during felling by about 50%.
· Half of the climbers not cut prior to
logging survived felling of their host trees and sprouted vigorously.
·
Poisoning cut climbers with 2,4,5-T usually prevented coppicing.
· Climber
cutting and poisoning productivity was 1 ha per 5 work hours.
· Concluded
that climber cutting prior to felling was a worthwhile silvicultural operation.
Appanah, S., G. Weinland, H.Bossel and H. Krieger. 1990. Are tropical rain forests non-renewable? An enquiry through modeling. Journal Tropical Forest Science 2(4): 331-348.
· Simulations show that a 35 year cutting cycle may be
too low in the selective management system (dipterocarps >60 cm dbh removed,
nondipterocarps >45 cm dbh removed, logging cycle 35 years).
· For the SMS
35 year cutting cycle, the logging results in continuous reduction in harvest of
emergents after every successive cutting.
· Another critical point stands out
clearly - in all simulations the pole regeneration is ephemeral in time and space. There is a clear danger in this: if cutting occurs when the poles are small in number or absent, then no residual stand will develop for the third cut.
Appanah, S. and M.R.A. Manaf. 1990. Smaller trees can fruit in logged dipterocarp forests. Journal of Tropical Forest Science 3(1): 80-87.
· A comparison of fruiting ability of dipterocarps in a
recently logged forest with that of an undisturbed and old regrowth forest.
·
In the recently logged forest the small dipterocarp residuals (>25 cm dbh)
could fruit (i.e., to produce seedlings for the 3rd cycle).
· By comparison,
equivalent sized trees in the old regrowth and undisturbed forests did not; here
fruiting trees were >35 and >50 cm dbh, respectively.
· Results suggest
that dipterocarp forests are potentially capable of regenerating within a few years after logging, on the condition sufficient advanced residuals are present.
Appanah, S. and G. Weinland. 1990. Will the management systems for hill dipterocarp forests, stand up? Journal of Tropical Forest Science 3(2): 140-158.
· This paper describes the Selective Management System
(SMS) of Peninsular Malaysia Hill forests in Peninsular Malaysia, the Indonesian
Selective Cutting System (ISCS), and the Philippine Selective Logging System
(PSLS).
· SMS consists of a logging cycle of 25-30 years, and the minimum economic cut is presently at 30-40 m3 /ha of currently commercial and utilizable species:
o SMS and selective fellings are the principal management systems for dipterocarp forests throughout Southeast Asia, although, some lowland dipterocarp forests are still being managed under the Malayan Uniform System (MUS).
o In the SMS all commercial species above 45 cm for non-dipterocarps and 50 cm for dipterocarps are felled, while maintaining minimum stocking levels of trees/ha in >45 cm, 30-45 cm and 15-30 cm classes. There is also a sequence of post harvest operations that should be carried out (e.g., pre-felling inventory, climber cutting, tree marking)
· In the PSLS a logging cycle of 30-40 years with suitable tending is used.
During the first silvicultural operation only 30% of trees with dbh between 15-65 cm and 60% of trees of 65 cm dbh and over may be felled.
In the Mindanao area yields have been 100-120 m3/ha but such high yield forests have dwindled quickly.
For PSLS to be successful need an effective monitoring system and logging damage must be drastically reduced.
At present the logging intensity is 70-90 m3/ha on a logging cycle of 35-40 years, but it is felt this should be corrected downwards or the cutting cycles extended (Lamprecht 1989)
· The ISCS is a much simpler system than the PSLS.
The forests in East Kalimantan are much poorer than those in the Philippines, so only 10-15 stems/ha (about 100 m3/ha) are extracted.
· Important to all selective cutting is to retain
sufficient numbers of trees in the 30-45 cm dbh class that will form the trees
harvested in the second rotation. Also, sufficient seed trees are needed to
regenerate the area.
· However, all the necessary silvicultural treatments,
directional felling, protection of advance growth, proper selection of trees to
not reduced genetic quality of the forest, etc. are not currently done, so the
current selective systems are not sustainable on a 35-40 year cutting
cycle.
· The lack of linkage between logging operations and silviculture
considerations is potentially destructive to the forest; more is left to chance
than to design.
· Many studies refer to an average diameter growth rate of
0.8-1.0 cm/year. These references generally link back to a UNDP/FAO project in
1978, which has be criticized by Wyatt-Smith (1988) as being of dubious
nature.
· While these growth rates of vigorous individuals may be possible on
the bests sites, on average, it is unlikely that dipterocarp forests of Malaysia
can reach these growth rates (gives values from yield plots ranging from 0.3-0.9
cm/year.
· In SMS logging damage to residuals is estimated at about 30% for
trees above 30 cm dbh, however, in many cases this is exceeded and it does not
take into account mortality occurring several years after logging.
· Another
problem is that the selective system is applied everywhere without taking into
account the condition of the stand (growth potential, tree form, damage,
adequacy of
numbers); it should be an option which is applied where most
suited and a varied of systems should be employed.
· For SMS to work, firstly and of immediate concern is the improvement of logging practices.
Armstrong, S. & Inglis, C.J. 2000. RIL for real: introducing reduced impact logging techniques into a commercial forestry operation in Guyana. In: International Forestry Review 2(1): 17-23.
· Commercial species were Baromalli and Trysil (12%
of basal area).
· The harvesting intensity was 8.2 m3/ha (2.4 trees per hectare).
· Vine cutting took
place 6 months before harvesting; it was only feasible to cut those around trees
identified for harvesting.
· A tendency to produce an inefficient skid trail
design exists where no pre-harvest tree location map is used.
· With
conventional logging practices the volume lost as waste wood was 3%.
·
Observations suggest that trained and experienced fellers can reduce the
incidence of wood loss significantly.
· With RIL, no merchantable trees were
missed in the block.
· The time requirement for conventional felling was 3
minutes/tree, for directional felling it increased to 7 minutes/tree.
· A 30%
reduction of skid trail length seems possible by providing a tree location map,
basic training and increased supervision.
· RIL techniques reduced the
bulldozer time for positioning the log for extraction from 8 to 2.5 hours/100
logs.
· Additional costs are associated with the pre-harvest inventory
required for RIL.
· If the value of the increase in production is taken into account, the adoption of RIL significantly reduces the production costs per m3.
· At the company level, increased production per block reduces the area of forest needed per m3 harvested; additional cost reductions are achieved in road construction, maintenance and hauling costs per m3 produced.
· The most severe damage resulted
from the use of bulldozers (skid trail construction, positioning of log for
extraction).
· Damage caused by clearing trees with attached vines during
skid trail construction was significant.
· Fellers are proficient at
identifying the most common commercial species; therefore training fellers in
spotting other commercial species should reduce the volume lost in this way.
· Improved efficiency of skid trail construction implies reduced damage and
reduced cost at the operational scale.
· An instructive exercise for any
commercial operation will be to assess the quantity of merchantable wood left in
a recently closed harvesting area as well as the extend and layout of skid trails.
Ayres, J.M. and A.D. Johns. 1987. Conservation of white uacaries in Amazonian várzea. Oryx 21(2): 74-80.
· Current average extraction rates of 4-5 trees/ha have
caused a total loss of only about 5% of standing trees in restingas (narrow
interlinked corridors of trees located on alluvial levées where trees are felled
during the low water period and floated out during high water).
· In nearby terra firme forest, removal of the same number of trees causes a total loss of 60% due to the heavy logging equipment, landings and roads.
Bach, C. F. 1999. Economic incentives for sustainable management: a small optimal control model for tropical forestry. Ecological Economics 30: 251-265.
· This model
analyses several options to make it profitable for the concessionaire to
undertake low impact logging activities (without any further control).
· The
model is based on an average concession of 10,000 ha in Ghana.
· The
concession is operated on a 40-year felling cycle.
· Cost data in this model
stem from a detailed survey of one of the largest timber companies in
Ghana.
· Revenue data are based on a survey of prices and end-uses for all
timber species.
· Around 1/3 of the trees >50cm dbh are allocated for
harvest; the growing stock of commercial species is fairly low.
· There is a
lack of economic incentives for the concessionaire to introduce RIL
techniques.
· The implementation of RIL techniques would require additional
investments in planning, training and the construction of roads and trails.
·
Economic incentives could be established either through direct area-dependent
payments or through higher prices.
· Logging without any consideration of
future growth will damage 40% of the stand, conventional logging as practised in
Ghana will damage 30%, while reduced impact logging will damage only 20% of the
stand.
· Costs are assumed to consist of fixed costs per hectare and variable
costs depending on the amount harvested. The variable component covers all
variable costs in extraction, hauling and processing.
· The highly volatile
exchange rate of cedis to US$ has a major impact on the absolute profitability
in production. However, the relative profitability remains unaffected.
·
Increased costs in sustainable management often stem from activities such as
training, mapping, inventories and proper construction of skid trails and roads.
These costs will be mostly independent of the volume extracted.
· Simulation
and results for net present value:
Net present value (US$ million) | |
Simulation 1: base-line. Yield allocation. Discount rate 5%. No subsidies. |
1.51 |
Simulation 2: low damage. Yield allocation, Low damage level imposed. No subsidies. |
0.81 |
Simulation 3: area-dependent subsidy. Yield allocation. Direct area-dependent subsidy to effort of US$ 92.5/ha. High effort level maintained in the first 60 years. |
1.51 |
Simulation 4: price subsidy. Yield allocation. Price subsidy of 147%. High effort level maintained in the first 60 years. |
26.68 |
Simulation 5: no yield allocation. No yield allocation. No subsidies. |
1.65 |
Simulation 6: discount rate of 10%. Yield allocation. No subsidies. Discount rate 10%. |
0.99 |
· Simulation 2: The concessionaire would certainly
attempt to avoid the extra costs. A tension occurs between short-term
profitability and long-term sustainability.
· Simulation 3: It is possible to persuade the concessionaire to reduce damage with an area-dependent subsidy of US$ 92.5/ha. At effort costs of US$
9/ha there is no reduced impact logging, because the benefits only occur 40
years later. At a discount rate of 5%, the net present value of these benefits
is marginal.
· Simulation 4: If the price of the effort to reduce damage is set to one, prices must be raised by 147% in order to persuade the concessionaire implement reduced impact logging. This is
equivalent to an additional US$ 3,157/ha for the first year. The concessionaire
will not compare his net present value with a price subsidy with that seen in
the base line, but only with the net present value if he received the price
subsidy but continued with a low effort and a high damage level.
· Simulation
6: An increase in the discount rate will increase the incentive to fell a larger
area and/or higher volume per hectare and thus increase the risk of
unsustainable management practices.
· Without compensation it will be
difficult to impose even small additional costs in harvest operations.
·
There is no reason to undertake low impact logging practices if no future
harvest is expected on the area (e.g. because of an expiring concession). In
these cases, at the end of the concession period the forest has no value for the
concessionaire.
· The growing stock of the most valuable timber species is
improved by 30-50% if reduced impact logging is introduced.
· Target
subsidies fit well into the current institutional set-up, encompassing logging
manuals, detailed topographic maps, post-harvest inspections and royalty
collections.
· Subsidising the costs connected with reduced impact logging
through area-dependent subsidies is by far more efficient than subsidising
prices of tropical timber.
· Marn and Jonkers (1981) find that in Sarawak,
conventional logging will severely damage 60 trees/ha of commercial species
(harvesting intensity 13.33 trees/ha). With well planned, supervised harvesting
and directional felling the loss will be reduced to 40 trees/ha. With a harvest
intensity of 2 trees/ha, the loss due to damage is 9.5 trees/ha. 80% of the damaged trees are in the diameter class of 10-40cm.
Baharuddin, K., A.M. Mokhtaruddin and M. Nik Muhamad. 1995. Surface runoff and soil loss from a skid trail and a logging road in a tropical forest. Journal of Tropical Forest Science. 558-569.
· Study in the tropical forest of Malaysia, and total
annual rainfalls for the two-year study period were 3084 and 2308 mm/year,
respectively
· Results from a two-year study revealed that the average
surface runoff from the undisturbed forest, skid trail and logging road were
62.9, 391.4 and 545.2 mm/year, respectively; the values correspond to 2.3, 14.5
and 20.3% of the total rainfall
· The surface runoff generated 453.7, 10069.7
and 13340.7 kg/ha/year of soil loss from the undisturbed, skid trail and logging
road, respectively in the first year after logging
· In the second year soil
losses decreased by 80% to 211.3 kg/ha/year for the skid trail and by 77% to
3146.7 kg/ha/year for the logging road
· Drastic reduction in the soil loss
was probably due to the rapid recovery in soil stabilization arising from fast
re-establishment of ground cover and emergence of seedlings on the logging road
and skid trail
· Plant and litter cover were shown to be the greatest
deterrent to surface erosion|
· Soil losses in the logging road and skid
trail increased up to a 20% slope, after which there was a rapid increase in soil loss; recommended that skid trails and logging roads not be constructed on slopes exceeding 20%
Baidoe, J.F. 1970. The selection system as practiced in
Ghana. Commonwealth Forestry Review 49(1): 159-165.
· Selection system as
practiced in Ghana in 1970 dates from 1956.
· It should involve stock mapping
(detailed mapping of location and description of all commercial trees) of all
economic trees >7 foot girth (68 cm dbh), improvement thinning of immature
trees, vine cutting and selective cutting on a 25 year cycle.
· 26 out of 190
tree species that grow to timber size are economically valuable.
· 2.5-5.0 trees/ha that are exploitable.
Balachandra, L. 1988. Buttresses on trees of Andaman and Nicobar Islands. Journal of the Andaman Science Association 4(2): 124-127.
· The volume of timber remaining in the forest in the form of buttressed stumps was 8.2 m3/ha for `hardwoods' and 5.89 m3/ha for `softwoods'.
·
Removal of buttresses before felling would minimize timber damage, increase
timber yield and keep the forest floor in a more hygienic condition.
Barreto, P., Amaral, P., Vidal, E. and Uhl, C. 1998. Costs and benefits of forest management for timber production in eastern Amazonia. Forest Ecology and Management 108 (1-2): 9-26.
· Current logging practices in eastern Amazonia are
careless, resulting in much unnecessary damage.
· This study compared the
net present value for 20- and 30 year cutting cycles with and without forest
management (planned and unplanned logging operations).
· The costs to plan logging operations were estimated at US$ 72/ha or approximately US$ 1.80 to 2.50 per m3 for harvesting intensities of 35-40 m3/ha.
· More than 90% of the planning costs
occurred in tree mapping, vine cutting, and planning logging manoeuvres (skid
trail layout, felling angle determinations).
· The careful planning of tree felling operations resulted in a 15% increase in productivity (m3 felled /work hour) when compared to unplanned
harvesting operations.
· The machine time (min/m3 harvested) necessary to open logging roads and log
landings was 37% less in the planned operation than in the unplanned
operation.
· The productivity of skidding logs to landings (m3 hauled/hour) was 27% greater in the planned
operation using wheeled skidders, compared to standard bulldozer-based
extraction in unplanned operations.
· In absence of planning 26% of the
felled volume of timber was wasted (7% due to poor felling techniques, 19%
simply lost because felled trees were never found by the tractor operator).
·
Using RIL techniques only 1% of the felled timber was wasted.
· Overall, increased work productivity and reduced waste in the RIL operation resulted in financial benefits of US$ 3.7 per m3, which was
approximately two times the cost of planning.
· RIL techniques reduce damage
to the forest, leaving a well-stocked stand.
· Good residual growing stock
combined with silvicultural treatments following logging should result in
greater timber production in managed forests.
· It was estimated that with
forest management 68% more timber volume could be extracted over a 30-year
period than without management. Using discount rates ranging from 6 to 20%, the
estimates of the net present value of timber extraction with forest management
were 38 to 45% higher than without management.
· However, any investment in forest land is perceived as risky because of frequent disputes over land ownership.
Bariteau, M. and J. Geoffroy. 1989. Sylviculture et regeneration naturelle en foret Guyana's (Silviculture and natural regeneration in the forests of French Guinea). Revue Forester Franchise 41(4): 309-323.
· The study of regeneration under three logging
intensities.
· Average volume in area (dbh _ 10 cm) was 350 m3/ha with a basal area of 31 m2/ha.
· The base treatment removed 33 m3/ha (2.6 m2/ha
BA).
· Other treatments removed various amounts for fuelwood and through herbicide treatment.
Barros, A.C. and C. Uhl. 1995. Logging along the Amazon River and estuary: patterns, problems and potential. Forest ecology and management 77: 87-105.
· Para State.
· Well-capitalized wood industries go
as far as 500 km into the forest in search of mahogany (Verissimo et al.,
1995).
· Paper outlines logging techniques used.
· Small mill (circular saw, family run, n=60) producing rough saw wood, generally for local markets, required on average 1850 m3 of logs for 650 m3 of sawn wood per year (= 35.1% LRF).
· Medium size mills (generally one band saw, 30 people employed, n=41) required on average 10200 m3 of roundwood to produce 3500 m3 of sawn wood (= 34.3% LRF).
· Veneer and plyboard mills (n=5) 91000 m3 for 33850 m3 of processed wood (=37.2% yield), logs floated from
as far as 2500 km away.
· In the varzea forest the average logging intensity is 56 m3/ha/entry (N. Maciel, pers.comm.
1994).}
· In the terra firme forest the average logging intensity is 38 m3/ha/entry (Verissimo et al. 1992).
Berthault, J.G. and P. Sist. 1997. An experimental comparison of different harvesting intensities with reduced impact and conventional logging in East Kalimantan, Indonesia. Forest Ecology and Management: 209-218.
· Study comparing conventional to RIL logging.
· Original density 530 +- 63.3 stems/ha; BA 31.4 +- 3.2 m2/ha.
· Harvest ranged from 5 to 15 stems/ha (43 to 174 m3/ha or 9.8 to 30 m2/ha).
· Felling mainly injured trees (especially
crown damage to trees 30-50 cm dbh), whereas skidding was the main cause of
mortality (especially uprooting and to trees 10-20 cm dbh).
· There was a
higher percent of damage to trees in the middle size classes; 74.5% of trees
killed were 10-20 cm dbh, but this class only holds 63% of trees.
· RIL
reduced damage or death to trees from 48.4% to 30.5% (i.e., extra 95 trees/ha
>10 cm dbh remained undamaged).
· In Borneo, damage often exceeds 50%,
which is more than in Africa or South America.
Bethel, J.S. 1984. Sometimes the word is "weed": a critical look at lesser-known species. Unasylva 36: 17-22.
· Lesser known species or secondary species is a
phenomenon wherever "forest exploitation" as a method of forest use occurs.
·
Forest exploitation involves the search for merchantable species and specimens
from among the trees that happen to occur in natural or secondary forests.
·
Forest management, on the other hand, involves growing trees that are known to
be merchantable.
· When the exploitative use of the natural forest does not
provide enough products to meet the demands of society, it may become both
feasible and desirable to grow a crop of trees in a managed forest to serve as
raw material for a forest-utilization system responsive to social
preference.
· When the quantity of preferred trees becomes scarce, there is
always the temptation to augment the timber production by attempting to market
less-preferred species.
· Utilization level of some humid tropical forests in Southeast Asia and Latin America varies from 4 to 48 m3/ha.
· When timber is harvested from exploitation
forests, the final yield of product from a tree is often as low as 10 to 20% and
typically averages no more than 30%.
· Forest inventory practices often
include utilization standards that are totally unrealistic in terms of
commercial feasibility.
· Failure to recognize that most tree species in a
mixed-species tropical-hardwood forest occur so infrequently, intermittently and
irregularly in a harvesting operations that it is virtually impossible to
develop around them a viable product-manufacturing operation.
· There is too
much wishful thinking on the prospects for developing instant new markets for
previously unknown and unmerchantable species.
· There are often too many
unrealistic expectations about the impact of new manufacturing technology on the
utilization of currently unmerchantable woods.
· New manufacturing technology
is typically developed to improve the use and merchantability of woods that are
currently well known and accepted in the market.
· Manufacturing processes
that are indiscriminate with respect to species are usually also those that
require very large capital investments - something that is sometimes not readily
available in developing countries.
· Usually more economically advantageous
to supply a mill with a uniform raw material, even though it may be able to
handle mixed species.
· There has been major success in the use of
underutilized species: e.g. western hemlock for pulp, aspen in OSB and pulp,
birch in pulp.
· The danger in placing too much emphasis upon the development
of new products from currently unused or under-used secondary species is that it
provides an excuse for allowing productive forest land to be occupied by weeds
on the remote chance that tomorrow they will not be weeds (also feel there is no need to regenerate the desirable species - poor management and sustainability of operations in the forest).
Bhargava, S.K. and F. Kugan. 1988. Development of forest sector planning, Malaysia: assessment of logging waste and mill residues in Sabah. Food and Agriculture Organization of the United Nations, United Nations Development Program, FO:DP/MAL/85/004, Working Paper 4. 26pp.
· Study of stump area logging waste in previously
unlogged and logged forests in flat, medium and difficult terrain in Sabah. On
average the waste amounted to 18.3% of the actual log production (Bhargava and
Kugan 1988). Bhargava and Kugan (1988) also found that on average 9.4% of the
actual log production was left as residues in the landings, and that almost 54%
of the residue logs observed were free of any defects. The total utilizable
waste based on removed log volume was 27.7%.
· Of a total harvest of 9.81 million m3 (1986), 2.72 million m3 is utilized waste left in the forest.
· Logging
residues were all pieces of timber >2 m in length and >45 cm
diameter.
· The cm dbh diameter felling limit =114,520,000 m3.
· If 40 cm dbh felling limit the volume would be 169,000,000 m3.
· Plantations of cocoa, rubber and oil palm expected to yield 30-40 m3/ha/year.
· Sawmill recovery 50% and waste 50%
(edges 12%, slabs 14%, off cut 7%, sawdust 12% and bark 5%).
· Plywood mill
recovery 44% plywood, wood residue 45% (log trim 4.4%, cores 5.9%, undried
veneer 24.1%, dried veneer 8.5%, sander dust 2.1%), bark 11%.
· Of 1.9 million m3 fed to sawmills, and veneer and plywood mills, 0.68 million m3 are left as
unutilizable.
· Total usable logging waste and mill residues amount to 3.4 million m3 annually.
Blanche, C.A. 1978. An overview of the effects and implications of Philippine selective logging on the forest ecosystem. BIOTROP Special Publication 3: 97-109.
· The Philippines, motivated by an overwhelming desire
to curb the rapid depletion of her forests, has embarked on "selective logging
system" as a means of achieving sustained yield.
· Theoretically any
silvicultural system is sound; it is when abused, misused and overused that
damages occur.
· Increasing horsepower utilization is directly related to the
degree of forest devastation.
· Regeneration of dipterocarps in a mixed dipterocarp forest (Quezon) is enhanced by the conditions present in a properly logged forest.
Blate, G. 1997. Sustainable forest management in Brazil. Tropical Forest Update 7(3): 14-15.
· This article summarises key findings of the IMAZON low
impact logging study.
· In conventional logging 7 m3/ha of wood were lost during skidding operations by not finding all felled trees while 0.3 m3/ha
were lost due to poor felling and bucking practices.
· Brazilian producers could yield an additional 7.3 m3/ha by
introducing reduced impact logging.
· Reduced impact logging damages 30%
fewer trees and disturbed 25% less of the canopy than conventional logging.
· With reduced impact logging, 5% of the area harvested were disturbed by
skid trails, roads and log decks.
· Reduced impact logging practices reduced
the machine time by 20%.
· Reduced impact logging practices may also reduce
cutting cycles by more than half. A harvesting cycle of 70 years for conventional methods may be reduced to 25-30 years through reduced impact logging.
Boerboom, J.H.A. and K.F. Wiersum. 1983. Human impact on tropical moist forest. In: Hozner, W., M.J.A. Werger and I. Ikusima (eds.). Man's Impact on Vegetation. Junk Publishers, The Hague, The Netherlands.
· A felling intensity of 5-8 trees/ha is considered to be sustainable for most types of tropical forests
BOLFOR, IURFO, CIFOR. Aplicación de la regencia forestal al manejo y aprovechamiento del bosque natural: caso de Costa Rica. BOLFOR, IUFRO, CIFOR. Santa Cruz de la Sierra, 1997.
· This study was carried out in the natural forests of
Costa Rica.
· The harvesting intensity for the first harvest in natural forests ranges from 40 to 60 m3/ha.
· Secondary forests are managed on a 15-year cutting cycle with a harvesting intensity of 20 to 30 m3/ha.
· Additional
costs are associated with the implementation of RIL ("buen manejo forestal")
techniques.
· A policyclic system was established in order to maintain
irregular structure and species diversity.
· Up to 60% of the commercial
volume may be extracted with a minimum harvesting diameter of 60cm dbh.
· Silvicultural treatments will be applied if necessary.
Borhan, M., B. Johari and E.S. Quah. 1987. Studies on logging damage due to different methods and intensities of harvesting in hill dipterocarp forest of Peninsular Malaysia. Malaysian Forester 50: 135-147.
· Logging with tractor and high-lead logging systems
(each with three minimum diameters between 45 and 60 cm dbh) in Peninsular
Malaysia compared for damage to seedlings, advance growth and soil.
· Damage
to seedlings in high-lead areas (50-57%) was higher than in tractor-logged areas
(38-48%).
· In the latter mortality was highest in the lowest size cutting
limits.
· Tractor damage at 60 cm min dbh led to disturbance of 17.81% of the
soil area.
· Damage to trees >10 cm dbh was higher with high-lead logging
(24%, 26%, 38 % with 45,60,52 cm min. cutting limits).
· With tractors damage to these trees ranged from 8% (45 cm min dbh) to 21% (60 cm dbh).
Bote, P.P. 1983. Financial feasibility of selective logging as a harvesting method in a virgin forest: the Taggat case. The Philippine Lumberman 29(10): 13-19, 35.
· Analysis of the financial feasibility of selective
logging in virgin dipterocarp forests of the Philippines.
· Prescribed
minimum number of healthy (uninjured) commercial residuals in 20-60 cm dbh
classes is 70% and for the +70 cm class 40% (assuming based on stems in original
stand).
· Supervised setting 21B8R had 71.7% (20-60 cm class) and 46.6% (+70
cm class)(7 ha).|
· Supervised setting 21C8R had 65.2% (20-60 cm class) and
40.0% (+70 cm class)(6 ha).
· Unsupervised setting 14 had 46.8% (20-60 cm
class) and 23.0% (+70 cm class).
· Unsupervised setting 13 had 26.1% (20-60
cm class) and 36.4% (+70 cm class).
· It is obvious that more wood volume or
more mature harvestable trees can be harvested during the first cut.
· Volume removed on 21B8R was 204.9 m3/ha and 120.2 m3/ha for 21C8R.
· ROI for set-up B8R was 317% and
for C8R it was 258% (i.e., money yield on wood harvested vs. harvesting
cost).
· Production costs and returns were similar in both supervised and
unsupervised settings
· The lower damage rates were due mainly to better
supervision.
· Sensitivity analysis showed that the production costs could
increase 30%, 30% decrease in yield and 20% fall in the product price and still make a profit.
Boulter, D. and D. Darr. 1996. North American timber trends study. United Nations, UN-ECE/FAO Timber Section, Geneva, Timber and Forest Study Paper No. 9.
· In Canada the m3 of roundwood required to produce 1 m3 of sawnwood or plywood fell from an average of 2.67 m3 in 1970, to 2.14 m3 in 1984, to only 1.98 m3 in 1996.
Bowyer, J.L. 1997. Strategies for ensuring the survival of tropical forests: can logging be one of them? Forest Products Journal 47(2): 15-24.
· Logging often results in significant
damage to the residual stand even when total deforestation is not the
outcome.
· IMAZON reported findings that forest damage associated with
conventional logging could be reduced by 30% through better planning or harvest
operations and better training of logging crews.
· Up to 19% of the harvest volume (7 m3/ha) was left behind after logging
because skidder operators could not locate the logs.
· With reduced impact
logging felling damage is minimal and soil disturbance is significantly reduced.
Brotoisworo, E. 1991. Indonesian forest resources and management policy. In: Howlett, D. and C. Sargent (eds.). Proceedings of Technical Workshop to Explore Options for Global Forestry Management, Bangkok, Thailand, April 24-30, 1991, International Institute for Environment and Development. p.254-262.
· The main (if not the only) forest management system
applied is the Indonesian Selective Cutting System and more recently modified as
the Indonesian Selective Cutting System and Planting System.
· Specifies a
minimum dbh felling limit of 50 cm and a 35-year logging cycle.
· Inefficient
logging practices have resulted in relatively high logging waste, i.e.
35-40%.
· There has been a stimulation of industries to use lesser known
species and residual wood as raw materials.
· Low skill of logging workers
has caused much damage in the forest in the past.
· Concession rights are
only valid for 20 years, while the cutting cycle stipulated by law is 35 years.
The resulting lack of interest on behalf of the concessionaires has led to
overcutting and relogging, aggravated by lack of knowledge about enrichment
planting, tending residual stands.
· The Ministry of Forests has recently
taken serious measures including cancellation of concession rights, and fines
for non-compliance with regulations.
· New regulations to modify the
Indonesian Selective Logging System specify that pre-felling inventories must be
made to assess whether residual stands contain an adequate stocking of 25 at
least 25 undamaged trees per hectare, of desired species of 20 cm dbh and larger, which can be harvested economically within 35 years. If this is not the case then enrichment planting has to be undertaken.
Brown, S. and A.E. Lugo. 1990. Tropical secondary forests. Journal of Tropical Ecology 6: 1-32.
· Forest structure and growth (all trees to a minimum 10 cm dbh) of some secondary forests:
Commercial volume, m3/ha |
Volume increment, m3/ha/yr |
Time period, years | |
Tropical very dry forest1 - fire, grazed and logged (2 entries) - undisturbed (average of 2 stands) |
31.3 25.0 131.0 |
0.58 0.31 3.36 |
15.2 15.2 4.0 |
Tropical dry forests1 - fire, grazed - fire, grazed, logged (2 entries) - undisturbed (average of 6 stands) |
103.2 111.8 137.3 208.0 |
2.07 1.75 1.64 4.40 |
9.8 8.1 6.2 17.0 |
Tropical montane moist forest1 - logged - undisturbed (average of 3 stands) |
120.3 368.0 |
4.20 4.15 |
23.9 14-24 |
Tropical wet forest2 Managed forest (with 8-9 native commercial species), 15 years - sand bank near river - plateau |
507 410 |
33.8 27.5 |
- - |
1Veillon, J.P. 1985.
El creceimiento de algunos bosques naturales de Venezuela en relación con los
parámetros del medio ambiente. Revista Forestal Venezolana 29: 5-122.
2Rosero, P. 1979. Some data on a secondary
forest managed in Siquirres, Costa Rica. In: Kunstadter, P., E.C. Chapman and S. Sabhasri (eds.). Workshop: agroforestry systems in Latin America. CATIE, Turrialba, Costa Rica. P.209-210.
· Rates of wood production based on short-term
measurements (1-2 years) are variable and range from 2-11 t/ha/year, which are
greater than in mature tropical forests of 1-8 t/ha/year.
· The factors for
converting commercial volume to wood biomass = 1.1 for dry and moist forests and 0.9 for wet forests (or for biomass to volume 0.909 and 1.111, respectively).
Bruenig, E. 1996. Conservation and Management of
Tropical Rainforests: An Integrated Approach to Sustainability. CAB
International, University Press, Cambridge, UK. 339pp.
· Overlogging
removes more than 50%, and up to 80-90%, of the canopy, completely altering the
structure and function of the ecosystem.
· Cutting and smashing of the
intermediate trees, which are the fastest growing part of the growing stock, and
destroying a large proportion of the regeneration reduces tree increment far
below the site potential.
· Wasteful harvesting and so-called volume
adjustment and illegal removal cause the forest areas to be logged two to three
times faster than necessary.
· More difficult is the assessment of the
present value of losses of future increment and yield caused by overuse, misuse
and mismanagement, and of the consequent reduction of employment and economic
activity in the future.
· Low-yield logging in the more strongly successional
African rainforests is, in every respect, a fundamentally different matter from
high-yield logging in Malaysian MDF or Peatswamp forest.
· Selective logging
in Africa has little effect on the ecological conditions of the forests that
retains its resource value, assuming that a wider range of tree species will
become marketable in the future.
· The conclusion is that the current system
of selective logging is socially harmful and requires fundamental changes of
harvesting, management and infrastructure, and the upgrading of moral attitudes
and professional performance of concession owners, managers, technicians,
labourers and government.
· If current conventional selective logging
continues, at least in Malaysia, the supply potential would be reduced to half
or one-third of the sustainable potential under a proper selection silvicultural
system.
· Felled trees, not the forest, should be utilized more thoroughly.
Recovery rates are badly in need of substantial improvement. The timber must be
better graded at source to be sold in the most lucrative markets. At present,
high-grade tropical timber is sold in low-price markets as commodity timber in
competition with cheaply produced temperate and subtropical plantation and
natural-forest hardwoods and softwoods.
· Planning is the most essential
function to be performed in logging business (Conway 1986).
· The intensity
and kind of harvesting must be fully compatible with the objectives of
silvicultural stand management.
· Ideally, the residual stand must include
the fast growers in the 40-80 cm diameter range and damage to the residual trees
and the soil must be kept to the absolute minimum.
· In conventional
selective logging with crawler tractors, loosen, move and compact the soil on
20-60% of the area .
· At the common cutting rate in MDF of 10-20% of the
volume, proper selection felling with extraction by crawler tractor, damages
20-30% of the basal area of the residual stand. The damage rapidly increases
with intensity of cut, at 50% removal reaching 70-80%. Beyond this, the falling
crowns and skidding smash practically the whole residual stand.
·
Conventional selective logging as currently practiced causes 70-80% damage with
only 10-20% basal area removed.
· State-of-the-art, traditional, well-planned
and skilful harvesting, more recently termed reduced impact logging (RIL), is
the most promising and immediately effective strategy within forestry towards
sustainability. It is cost-neutral, costs of planning and supervision being
balanced by savings in operations and higher out-turns.
· RIL has a long
tradition in tropical and temperate forests, the essential condition is to
integrate harvesting with management planning, execution, monitoring and
control.
· Essential technical features of RIL are: pre-felling survey and
mapping of topography, site and growing stock, technical planning of access and
extraction, including roading and drainage specifications, pre-felling climber
cutting, direction felling towards planned skid trails and multiple impact
zones, but away from streams, low stumps, efficient utilization of the felled
trunks, minimized width of road and skidtrails, proper winching, use of an
arch/fairlead/pan, no criss-crossing by tractors, slash management to reduce
fire hazards and water pollution, adequate safety and working conditions, and
general compliance with plans, rules and standards (these are age-old
traditional principles of orderly forestry).
· The adoption of the principles
of orderly harvesting makes social, economical, environmental and ecological
good sense.
· In RIL at least 20-30% fewer crop trees in the 40-60 cm
diameter class are destroyed or damaged, so that more larger timber of high
quality is produced in the next felling cycle.
· Putz and Pinard (1993) found
50% damage to the residual stand in conventional logging.
· Phillips (1993) found 43% residual stand damage in conventional logging (Sabah); on average 168 m3 of the growing stock was damaged or killed to harvest 54 m3/ha logs
· RIL can result in 50%
less damage to the residual growing stock.
· In current selective logging
20-50% of merchantable timber goes to waste due to poor standards of felling,
bucking and grading, carelessness, poor management and lack of supervision in
the felling areas.
· A post-logging survey of 7 ha of selectively logged MDF and Kerangas forest (KF) in Sabal Forest Reserve (RP 146) measured 15.2 m3/ha of merchantable log timber of good quality and sizes left behind (the amount extracted was 31 m3/ha), which results to 33% of the merchantable
felled trunks being wasted.
· The above waste could have been avoided with
RIL and more timber extracted, or less area harvested.
· In conventional
selective logging, no only the skid trails but also the roads are notoriously
badly aligned, drainage is poor and very ineffective, and the right-of-way
clearing is excessively wide (between 50 and 100 m wide).
· Tractor drivers
bulldoze their way from tree to tree without planning and without considering
the best extraction routes, causing particularly bad criss-crossing in easier
country (Yeo 1987).
· Another study in Sarawak showed that RIL reduced damage
to residuals by a third
· Replacement of the conventional practices of selective logging by RIL reduces the logging costs per m3 extracted timber by 20-30% and the damage to the
residual stand and the soil is reduced by at least 25-30%.
· It is
well-established knowledge from experience in temperate and tropical forestry
that well-planned and executed timber harvesting costs less than haphazard and
unskilled logging. However, this fact has been frequently questioned by
uninformed outsiders in discussions on sustainability. There is ample evidence
that the badly planned and organized conventional selective logging by crawler
tractor in the current fashion of roading and logging is more expensive with
respect to direct and indirect costs than proper, sustainable selection
harvesting and can be almost as expensive as helicopter logging.
· The
reasons are that work performance is extremely poor and inefficient, machine
wear and road maintenance are excessively costly, many of the internal costs are
not even accounted for, and externalities are ignored. Lack of skills and poor
management result in excessive soil movement and machine time usage in
road-making and log extraction. Poor standards of drainage, road and skidtrail
construction waste time and labour, and cause excessive wear of machinery.
Technically poor and badly maintained equipment and unskilled labour increase
machine wear, operation time and timber waste in felling, extraction and
transport. The rate of work-related accidents is extremely high, but hardly
appears as a cost factor.
· Many of these points also applied in the past to
the conventional practice of native "kuda-kuda" logging in Peatswamp forest.
Proper and orderly sustainable harvesting was introduced in the 1950's against
initial opposition by most concessionaires. The results were reduced costs,
improved working conditions and safety, and increased out-turn per felled tree,
improving overall private and social profit.
· Korsgaard (1985) concluded
from results of field work in Sarawak, "there is no reason to tolerate
harvesting operations that are wasteful and damaging."
· Marn and Jonkers (1981) study in Sarawak found RIL reduced skidding costs (-25%), skidtrail area (-22%), canopy opening (-44%), loss of commercial residuals (-33%), abandoned merchantable timber (-48%), cost per cubic meter extracted (-26%) and working time per m3 (-25.5%), when compared to
conventional selective logging.
· Putz and Pinard (1993) estimated the cost of RIL (1993 USD) as: $50/ha surveying and mapping, $10/ha for planning and marking skidtrails, $35/ha for directional felling, $40/ha for drainage of roads and skidtrails. The total additional cost was $135/ha or $1.70/m3, with a logging intensity of 80 m3/ha. However, this was the first time the crew had
implemented RIL and there were extra training and learning costs included in the
above.
· The above costs have to be weighted against the savings in
extraction costs, increase in timber recovery and gains in productivity.
·
Recent African and Amazonia studies corroborate the Malaysian experience, that
sustainable harvesting is more profitable and cost-efficient than the
conventional selective logging.
· Harvesting intensities of 40-60 m3 every 25 years as visualized in Malaysia would
certainly exceed the rates of replenishment of any of the nutrients.
· The tentative conclusions are that the gaps formed and the log timber extracted in selection felling (RIL) do not impoverish the nutrient stock, provided safe minimum standards per hectare are maintained: 0.1-0.3 ha gap area, 2-5 trees felled, 30-60 m3 extracted, >40-year felling
cycle.
· Selective logging with blanket application of a minimum diameter
limit as low as 50-60 cm in MDF, or even less in Peatswamp forest, removes
immature trees which are in the `great period of growth' with the highest
current rates of basal area, volume and value increment.
· The
fastest-growing trees with the highest volume and value increment in the `great
period of growth' between 40/50 and 70/80 cm diameter are cut prematurely in
ecologically excessive and economically unnecessary, heavy selective
logging.
· In heavy selective logging, PEP declines severely to as low as 50%
and less of the naturally possible volume and value increment.
· Excessive
and poor roading and skidding, heavy soil erosion and compaction, and damage to
immature residual trees depresses NPP and PEP still further to between
25-50%.
· Consequently in these types of situations felling cycles of 25-50
years are not sustainable and 60-100 years are more realistic (even longer on
poor soils).
· The first cycle of selective logging maximizes quick and easy
cash flow and profit for the concessionaire.
· Another example of indisciminate diameter limit cutting in Sarawak mixed Peatswamp forest - initial growing stock volume 357 m3/ha dbh >20 cm, felling intensity 28.4 trees per ha (42.4% of basal area), caused a canopy opening of 60-70%, 59.6% of residual growing stock severely damaged, 17.8% slightly damaged and only 8.2% undamaged, almost 200 m3/ha of logging slash was left.
· In Sabah,
research into logging damage, regeneration and growth after first cutting in MDF
began early in the 1950's.
· Experimental comparison of tree-species richness
in 20, 1 ha research plots in Liberia between primeval natural forest and
modified selection-harvested forests with and without silvicultural manipulation
has shown that 15-20 years after intervention no statistical differences in
tree-species richness and spectra exists between them (no species losses, except
for one species in one of the primeval control plots).
· The conventional
simple selective logging with 50-60 cm diameter limit and too-short (15-30
years) felling cycles, and clear-felling of rainforests over large tracts remove
the fast-growing and value-producing trees in the 40-80 cm diameter classes and
destroy the architectural and organizational structure of the ecosystem and the
PEP potential (PEP = primary economic productivity and NPP = net primary
production).
· A diameter limit felling of 50 cm is better than 40 cm, and 60
cm would probably yield even better results (Peatswamp forest in Sarawak).
· The felling cycle should be between 40 and 60 years depending on the species composition and silvicultural treatments, but not less (30 m3/ha logging intensity?).
· (Long list of
references) In spite of this well documented and solid base of practical
experience and guidance, dissemination of knowledge and enforcement of norms and
codes of conduct fell short almost everywhere, except in Queensland and in
individual concession areas of more committed companies. Forest misuse and abuse remained rampant, overlogging and underutilization persisted in tropical forests and elsewhere.
Bruijnzeel, L.A. 1992. Managing tropical watersheds for production: where contradictory theory and practice co-exist. In: Wise management of tropical forests. Proceedings of the Oxford Conference on tropical forests. Oxford Forestry Institute, Oxford. p.37-76.
· Covers all residual trees are damaged in polycyclic systems, and all residual trees are damaged in monocyclic systems.
Buenaflor, V. 1989. Logging in Papua New Guinea. Food and Agriculture Organization of the United Nations, UNDP/FAO Project FAO:DP/PNG/84/003, Working Document No. 15. 67pp.
· A critical review of uncontrolled logging operations
in PNG.
· Over 30% of most logged areas are destroyed by uncontrolled
skidding.
· Over 40% of the residual trees 20-50 cm dbh are damaged by
uncontrolled current logging.
· Minimum dbh for felling is 50 cm, although
for export markets operators do not generally fell trees below 60 cm dbh.
· Current average extracted volume is about 30 m3/ha, but can be as low as 15-25 m3/ha.
· Estimates that if RIL was used the harvest level could be 60 m3/ha after 30 years.
·
Outlines the RIL technique, including post harvesting assessment.
· Extractable volume in PNG forest averages 6-15 trees/ha or 20-60 m3/ha.
· Skid roads about 100-120 m/ha or 400-480 m2/ha (4.0-4.8% of area).
· Vanimo case
study: showed major impact due to non-compliance to the logging plan (e.g., road
right-of-way widths of 25 and 18 m, when 14 m was planned; skid roads were 5 m
wide when planned was 4 m; 20-30% of the area damaged).
· Wawoi-Guavi case study: the cost of 1.08 K/m3 (K=Kina) for forest planning and engineering was offset by a skidding productivity increase from 8.42 to 12.10 m3/MOH (44%) and a skidding cost decrease from 4.70 to 3.27 K/m3; in uncontrolled area 67% of residuals undamaged with logging intensity of 23 m3/ha, while 78% undamaged in controlled with logging intensity of 32 m3/ha; area damaged was 13.7% in uncontrolled and 11.0% in controlled.
Buenaflor, V.D. 1990. Forest management research and development, Papua New Guinea: report on improved forest harvesting. Food and Agriculture Organization of the United Nations, UNDP/FAO Project FAO:DP/PNG/86/009. 36pp.
· Project deals with Manus Province.
· Assumed a 30
year cutting cycle and 0.75 cm/year diameter growth in AAC calculations, along
with a 10% reduction for breakage and defects.
· Selective logging is not
seriously practiced by many logging operations in the country.
· No detail
plans for operations, boundary of the operational area is imaginary, no pre-laid
skid road, no marking of harvestable trees or felling directions, and minimal
follow-up in the field after logging.
· There is a need to change to RIL to
practice selective logging to perpetuate the forest resource and to maintain the
environmental stability of the area.
· Some of the trees in the 50-60 cm dbh
class need to be retained as future crop trees to maintain adequate forest cover
and seed trees.
· Outlines a suggested methodology to implement RIL and course field practitioners in RIL.
Buenaflor, V.D. and R. Heinrich. 1980. FMC tracked skidder logging study in Indonesia. Food and Agriculture Organization of the United Nations, Project FO:INS/78/054, working paper 7. 103pp.
· Tropical lowland tropical forest (with seasonal flooding) in Sumatra:
In logging area average volume extracted of 15.8 m3(sob)/ha (5 trees/ha with average tree size of 3.2 m3(sob)).
A bark allowance of 15% was made to obtain 12.7 m3(sub)/ha.
The study block had a lower logging intensity than in the other blocks, where it averaged 21 m3(sob)/ha or 18 m3(sub)/ha).
· Tropical high forest in steep terrain in South Kalimantan:
On average 146 m3/ha of commercial species with dbh >50 cm available, of which 120 m3/ha are dipterocarp.
In study area 10.37 trees/ha (dbh >60 cm commercial species) with a volume of 147.1 m3(sob)/ha (100% cruise of 500 ha area) was available.
Spur roads 6-8 m wide, and radius of clearing for log landings is up to 50 m (holds 50-60 logs at a times).
Skid distances average from 1000 to 2000 m.
Average road density is 15-20 m/ha.
In FMC areas the average skid trail density was 33.3 m/ha.
In FMC 100 ha area 198.04 m3/ha of which 155.11 m3/ha extracted (78% of total volume).
Buenaflor, V. and T.D.R.W. Karunatilleke. 1992. Harvest planning and operations study in wet zone natural forests, Sri Lanka. Food and Agriculture Organization of the United Nations, FO:DP/SRL/89/012.
· Most of the natural forests in the wet zone have been
logged a number of times and the growing stock has reached a very low level in
many areas.
· At present up to 70% of the wood being logged in natural forests is wasted owing to both the methods of harvesting and utilization, and the non-availability of markets for wood.
Bullock, S.H. 1980. Impacts of logging in littoral
Cameroon. Commonwealth Forestry Review 59: 208-209.
· Trees/ha (34 taxa, dbh>80 cm) extracted over a region of 474 km2
(range 0.1-4.0 trees/ha).
· Direct logging disturbance affected 8.4% of the
area.
· +- 14.7 m of tractor trail per tree extracted.
· The mean size of gaps was 400 m2 (n=100) with damage or death to
5.2 adjacent trees >25 m tall, and 6.2 trees between 15-25 m tall.
· Less
than 5% of the timber trees had lianas.
· Of 47,407 ha in region:
Area of compacted roadbed was 386 ha (0.8% of the region).
Area of road shoulder was 857 ha (1.8% of the region).
Area of trails was estimated 727 ha (1.5% of the region).
Area of tree fall gaps covered about 2001 ha (4.2% of region).
Burgess, P.F. 1971. Effect of logging on hill dipterocarp forest. Malayan Nature Journal 24: 231-237.
· On average 15 trees/ha felled (6 trees/acre).
· In
a study of a 100 acre logging site 35% (% of basal area) of the trees were
undisturbed, 55% were destroyed in the extraction process and 10% were actually
extracted.
· Road making is probably the greatest damaging factor in hill
forest exploitation.
· In general loggers pay little attention to drainage on
their roads, and the road is usually `daylighted' to a width of one chain on
either side by felling all trees and most undergrowth to enable the sun to dry
out the surface.
· Poison girdling, while it is an excellent silvicultural
practice when carefully controlled, does much to increase the loss of species in
exploited forest and by the long-delayed effects of the falling of poisoned
trees it extends the period of disturbance to the ecosystem.
Byron, N. and M.R. Perez. 1996. What future for the tropical moist forest 25 years hence? Commonwealth Forestry Review 75(2): 124-129.
· Virtually all pulp and paper and reconstituted panels
can be derived from plantations or from heavily modified temperate forests.
·
Tropical timber will increasingly change from a bulk commodity to an exclusive,
high-value product for niche markets in affluent countries.
· Any
interventions that reduce the commercial (or subsistence) value of TMF will
undermine the economic basis for their retention, thereby accelerating
conversion to agriculture.
· If logs become unsaleable for whatever reasons,
they may simply be burnt if forest conversion remains profitable, to whoever is doing it, due to the economics of alternative land uses and the rewards to `land-claiming'.
Cannon, C.H., D.R. Part, M. Leighton and K. Kartawinata. 1994. The structure of lowland rainforest after selective logging in West Kalimantan, Indonesia. Forest Ecology and Management 67(1-3): 49-68.
· Harvest removed 43% of the pre-cut basal area, and 62% of the pre-cut dipterocarp basal area (5.7 m2/ha in 6 months, 5.4 m2/ha in 1 year, 4.1 m2/ha in 8 years, mean 5.1 m2/ha)
· Residual dipterocarp trees <50 cm dbh
suffered high mortality after logging, possibly limiting future wood
production.
· On an average 76% of the crown cover had moderate to heavy
disturbance (45% heavy disturbance to the canopy).
· In the 6 month after
logging area 18.4% of the forest floor was disrupted by roads, tractor tracks
and skid trails, while after 1 year it was 14.0% and after 8 years 6.2% (lower
level partly due to lower logging intensity and partly to recovery after 8
years).
· The total basal area in the area 8 years after logging was still
only half of that found in nearby unlogged forest.
· Clear evidence of
vegetation recovery 8 years after logging, however, more than 8 years is
required for severely disturbed areas to recover any canopy structure beyond the
short-stature stands formed by pioneer species.
Canonizado, J.A. 1978.
Simulation of selective forest management regimes. The Malaysian Forester 41(2):
128-142.
· Data for simulations from 45 logging set-ups representing 2023
ha.
· Intensive logging damage surveys were made on 43 of the 45 logging
set-ups.
· No logging intensity data or residual stand information are
given.
· Average residual damage in contractor operated areas to dipterocarps
27.8% and non-dipterocarps 38.5%; and in company operations to dipterocarps
32.8% and non-dipterocarps 34.5%.
Catinot, R. 1994. Amenager les savanes boisees Africaines. Un tel objectif semble desormais a notre portee (Managing wooded African savannas. Such a goal now appears achievable). Bois et Forets des Tropiques 241: 53-70.
· In Cote d'Ivoire productivity is restored 9 years after logging and protection from brush fires increased the number of new stems 2.3-2.5 fold (increase in productivity from 1-1.5 m3/ha/year to 2-3 m3/ha/year (regions 700 mm rainfall/year) and 3-3.5 m3/ha/year (regions with up to 1500 mm rainfall/year)).
Cedergren, J., J. Falck, A. Garcia, F. Goh and M. Hagner. 1996. Impact of selective logging on silvicultural values in a mixed dipterocarp forest in Sabah. In: Proceedings of Forest Operations for Sustainable Forestry, XX IUFRO, World Congress, August 6-12, 1995. IUFRO S3.05-00 and CIFOR Publication. p.39-45.
· Study of 20 treatment plots, each 5.76 ha in
size.
· 310-440 trees/ha with dbh >10 cm, of which 10-20 stems/ha had dbh
>60 cm.
· Basal area was 28.3 m2/ha of
which 57% were dipterocarps.
· Minimum felling diameter in Sabah is 60
cm.
· 192 climbers/ha with diameter ranging from 2-32 cm, and dead trees
accounted for 3% of stocking.
· Felling intensities exceeding 100 m3/ha are common.
· Skid trail spacing was 60 m and
were planned.
· In directional felling 39% fell within 5º of intended lay,
63% within 10º of intended lay and 78% within 20º of intended lay.
· The
average felling range was 185º.
· Climber cutting had no effect on felling accuracy.
Chai, D.N.P. 1975. Enrichment planting in Sabah. Malaysian Forester 38(4): 271-277.
· Severe damage to the soil and the forest stand itself
has resulted from the recent widespread increase in the use of heavy logging
machinery.
· The total damage from logging amounts to as high as 30-50% of
the total land surface.
Chai, D.N.P. and M.P. Udarbe. 1977. The effective use of current silvicultural practice in Sabah. Malaysian Forester 40(1): 27-35.
· The greatest menace to the advance growth is careless
extraction rather than felling.
· Felling coupes selected two years in
advance and climber cutting done then.
· 25 commercial trees/hectare marked
for retention.
Chauvin, H. 1976. Opening up the tropical moist forest and harvesting the timber: factors conditioning methods and costs. Unasylva 28(112-113): 80-84.
· An essential feature in the harvesting of tropical
forests: the logger must also be a public works contractor.
· Successful
logging operations and a good network of trails depend essentially on a good
pre-harvest survey.
· The smaller the volume logged per hectare, the more
elaborate and complete must be the survey.
· Felling production is affected
much more by the organization of the work and by local habits.
· Skidding
operations represent from 20-40% of the cost of the wood delivered to
roadside.
Chim, L.T. and W.F. On. 1973. Density, recruitment, mortality and growth of dipterocarp seedlings in virgin and logged-over forests in Sabah. The Malaysian Forester 36(1): 3-15.
· Mortality of seedlings occurs continuously in the
regeneration pool but its rate rises after logging.
· In one study 13.7% of
the original number of seedlings present before logging were still alive 3 years
after logging (19350 seedlings/acre reduced to 2450 seedlings/acre).
· The
majority of the mortality occurred during logging (5350 seedlings/acre 1 year
after).
· There was no change in species composition of the live seedlings
though.
· Retention of relics as seed-bearers in open areas is relevant for
regeneration and should be enforced.
· Preferable to manage the regenerating
forest than plant dipterocarps in open areas; regeneration of bare lands has
been shown to be a slow process though some success may be achieved.
· Undue
destruction of regenerating forests should not be allowed and the Forest
Department should endeavour, as far as possible to impose rules and regulations
with respect to logging damage.
CIFOR. Annual Report 1998. Centre for International Forestry Research. 1998.
· The implementation of reduced impact logging
techniques can reduce impacts to the soil from heavy logging machinery by 25%,
and lead to a gain of as much as 50% in the "carbon storehouse" benefits from
the remaining vegetation.
· In some RIL experiments in lowland tropical
forests the damage to the soil and to advanced regeneration was reduced by 50%
relative to conventional logging.
Cordero, W. and A. Howard. 1996. Use of oxen in logging operations in rural
areas of Costa Rica. In: Proceedings of Forest Operations for Sustainable
Forestry, XX IUFRO, World Congress, August 6-12, 1995. IUFRO S3.05-00 and CIFOR
Publication. p.5-12.
· Logging intensity was 6 trees/ha in oxen logged
area and 7.33 trees/ha in tractor logged area.
· In oxen logged area logging
effect (based on number of stems) was 1.3% extracted, 11.85% very severe injury
or killed, 3.25% severe, 12.36% minor injury, 68.5% had no injury, and
non-logging damage was 2.75%.
· In tractor logged area logging effect was
4.82% extracted, 19.15% very severe injury or killed, 0.86% severe injury,
14.06% minor injury, 60.66% had no injury, and non-logging damage was 5.26%.
Crome, F.H.J., L.A. Moore and G.C. Richards. 1992. A study of logging damage in upland rainforest in north Queensland. Forest Ecology and Management 49(1-2): 1-29.
· Queensland Selective Logging System studied.
· Mean
removal was 6.6 stems/ha, 4.9 m2/ha basal area
and 37 m3/ha logs.
· 146.7 stems/ha were
killed during the logging amounting to 12 m2/ha
of basal area.
· Machine trails occupied 5% of the area.
· Damage was less
than in other studies done in S.E. Asia.
· Could have used more of the fibre
in the crowns (large branches).
· Most important to further reduce damage is
to enhance the skills, sensibilities and cooperation of field personnel.
·
Harvesting rainforest under a management system is now being recognized as
ecologically, economically and socially preferable to its conversion to
plantations and agriculture, particularly when the who range of values of the
forest is considered.
· Management systems that were being abandoned in many
countries are again being promoted.
· There are about 1 million ha of
tropical rainforest in Queensland, between Cooktown and Townsville.
· 3-years
before logging the area was surveyed and mapped and complete tree species lists
produced.
· All felled trees were located on a map, identified and measured
immediately after felling.
· Standing damaged trees likely to survive were
not enumerated.
· 121 marked trees and 5 salvage trees of 25 species were
harvested.
· Ridge sites had 23.3% of their total stems and 25% of their
total basal areas removed of which 57.6% was on harvested trees.
· Gully
sites lost 16.6% of total stems and 17.1% of total basal area yet only 42.4% of
this total basal area loss was on harvested trees - greater `incidental losses'
in gullies due to tree crowns falling from further up the slope.
· Logging
did not result in the loss of any tree species from the sample sites nor was
there any change in the total plant species list after logging.
· Of the 19
ha plot harvested, 3.7 ha of canopy (19.5%) was lost.
· There were 1600 m of
major logging tracks, averaging 5 m in width (0.8 ha) from which all vegetation
was cleared and with mineral soil exposed along their entire length = 4.2% of
area.
· An additional 530 m of minor tracks averaging 3 m wide (0.16 ha) were
made by the skidder (little exposed mineral soil and many seedlings and small
saplings remained) = 0.8% of area.
· 18 months after logging casual
observations indicated that there was little regeneration on the major logging
tracks.
· After log hauling was finished the QFS constructed drains across
the tracks and prohibited vehicle access - observations indicated that this, and
the banning of heavy machinery in wet conditions, were effective in reducing
erosion.
· The most significant factor in siltation of the stream, however,
was constant erosion from the busy main access roadside alongside the study
area.
· Data from various logging studies for comparison with data from the
logging area on the Windsor Tableland, north Queensland:
(note variable methodologies used in studies so data is not totally comparable between studies and incidental losses include both extracted and damaged trees)
|
Place |
Area (ha) |
Harvested (/ha) |
Incidental Losses (% BA) |
% canopy loss |
Area (%) |
Study | ||||
|
Stems |
m3 |
m2 |
Killed |
Damaged |
All Roads |
Minor Roads1 | ||||
|
Queensland Queensland Queensland Queensland Queensland Queensland Queensland Queensland Queensland |
5.6 1.6 0.1 0.4 0.6 0.3 0.2 19.0 16.5 |
26.0 32.7 39.5 18.9 25.6 18.2 19.8 6.6 7.6 |
66.0 36.6 42.1 |
15.4 24.8 7.3 11.4 8.4 9.0 4.8 5.6 |
16.02 29.9 21.3 16.0 29.4 28.9 35.8 18.1 20.4 |
18.2 19.4 22.3 |
26.0 |
4.3 4.8 |
Nicholson et al. (1983) 3 Nicholson et al. (1988) Nicholson et al. (1988) Nicholson et al. (1988) Nicholson et al. (1988) Nicholson et al. (1988) Nicholson et al. (1988) This study This study | |
|
Sabah Sabah Sabah Sabah Sabah Sabah Sabah Sabah Sabah |
43.7 8.1 8.1 4.0 4.0 4.0 4.0 4.0 43.7 |
11.6 15.3 16.6 19.0 9.1 12.8 11.9 16.1 11.6 |
47.2 |
58.04 40.04 51.04 43.04 47.04 29.84 |
45 |
14.0 |
Nicholson (1979) p.19 Nicholson (1979) p.19 Nicholson (1979) p.19 Nicholson (1979) Table19 Nicholson (1979) Table19 Nicholson (1979) Table19 Nicholson (1979) Table19 Nicholson (1979) Table19 Nicholson (1958) | |||
|
W.Malaysia W.Malaysia W.Malaysia W.Malaysia W.Malaysia W.Malaysia W.Malaysia W.Malaysia |
21.3 |
13.7 8.4 12.3 10.8 9.6 9.9 18.3 |
41.6 |
24.0 |
47.6 |
53.6 |
9.0 |
Nicholson (1979) Table 21 Nicholson (1979) Table 21 Nicholson (1979) Table 21 Nicholson (1979) Table 21 Nicholson (1979) Table 21 Nicholson (1979) Table 21 Wyatt-Smith et al. (1962) Johns (1988) | ||
|
Kalimantan Philippines Philippines Philippines Philippines |
2.0 10.0 22.2 7.6 7.6 |
11.0 24.6 19.8 20.5 7.2 |
244 222 187 |
12.0 |
30.0 |
Abdulhadi et al. (1981) Nicholson (1979) Table 26 Nicholson (1979) Table 26 Nicholson (1979) Table 27 Nicholson (1979) p.29 | ||||
|
Amazonia Amazonia |
6.8 52.0 |
8.0 4.3 |
52 31 |
11.0 |
28.0 |
46.3 |
8.0 |
4.0 |
Uhl and Vieira (1989) Uhl and Vieira (1989) | |
1Roads too small to
allow logging trucks
2Stems over 20 cm
3Virgin plots on granite only
4Commercial stems only
· Average volume logged throughout the Windsor Tableland
was 50 m3/ha and some areas logged before 1982
yielded as much as 66 m3/ha.
· Other
Queensland studies would have had strict control over the timber cuttings and
bulldozer drivers at all times, also machinery would have been smaller and more
winching done.
· 18 months after logging casual observations showed that
there was a dense growth of Stinging Tree and rattans in large gaps.
· There
could be more use of the felled trees. Much timber was left in heads and large
limbs and this could have been harvested with no increased incidental
damage.
· In the past when smaller machines were used, winching over long
distances was commonplace. Also had a helper to pull out the cable and guide the
logs around residuals. Now the tractor driver has to do all this himself.
·
In spite of close supervision by QFS personnel the rules were not always obeyed
and the decisions of the company staff and/or contractors resulted in incorrect
placement of the
loading area, increased roading, increased incidental losses
and stream siltation.
· This indicates how important the skills and attitudes
of field personnel are and, above all, how willing they are to obey the
strictures in the logging plans.
· The field operators have the power to
exacerbate or ameliorate the environmental damage caused by logging and their
management determines the success or otherwise of management plans.
Dawkins, H.C. 1958. The management of tropical high forest, with special reference to Uganda. Imperial Forestry Institute, Oxford, U.K., IFI Paper 34. 155pp.
· Area of damage associated with the removal of one tree
of 70 cm dbh is not likely to be less than 200 m2 (tree with 8 foot girth (78 cm dbh) will
irreparably damage at least 0.05 acre (202m2) of
pole and adolescent stock).
· Classes the Queensland system as complicated to
illustrate as a scheme, being based on a polycyclic system of management and
supported by exceptionally skilled field staff.
· In one study the mean
felling damage per tree was 0.1 ac (405 m2), and
could have been reduced to one-half of this through directional felling.
· If
basal area is >140 ft2/ac trees of THF are
incapable of satisfactory growth.
· Basal area should be between 80 to 120
ft2/ac to attain one foot girth growth per ten
years.
· Presents a calculation of the impact of felling 10 trees/acre of 8
ft girth on a 40-year cycle (i.e., MAI 30 ft3/acre/year = 2.1 m3/ha/year), and shows that crown damage to pole size
timber is so high that this yield is just achievable with careful directional
felling (i.e., with careful felling gap opening of 0.05 acres/tree felled = 0.5
acres impacted).
· Any polycyclic system aiming at a MAI of greater than 2.1
m3/ha/year will be difficult as it is bound to
require more intense and more frequent felling than every 40 years.
· Partly
because of the above reasoning the uniform system is recommended.
DeBonis, J. 1986. Harvesting tropical forests in Ecuador. Journal of Forestry 84(4): 43-46.
· Extraction is performed with ground-skidding
equipment; the most common being large rubber-tired skidders .
· Report
describes a conventional unplanned and uncontrolled logging operation in the
tropics.
· Due to the haphazard nature of the operations 40% or more of the
ground surface area is disturbed.
· In wet soil conditions bulldozers dig out
trails to mineral soil to a depth of 0.25-0.5 m.
· On slopes of over 10%
trails are dug out even deeper in the hope of better traction.
· The amount
and intensity of damage is amplified during wet-weather skidding, where up to
75% of the area can end up covered by skid trails (trails are used until they
become troughs of mud 1 m or more in depth, incapable of being reclaimed.
·
When operating during the wet period, one company experienced a 100% increase in
machine maintenance and repair costs, while productivity decreased to as low as
15% of average dry season productivity.
· Preplanning skid trails and
directional felling could reduce the area covered by skid trails to 15%.
· By
restricting skidders to skid trails and requiring more winching the disturbed
area could be reduced to as low as 4%, depending on skid trail spacing.
·
Sawyers receive no training in felling or bucking and their is considerable
wastage due to poor trimming (i.e., log lengths not measured) and felling (e.g.,
no hinge to control felling direction).
· With the use of proper felling and
bucking technique at least a 15-30% increase in wood volume at the mill could be
realized.
· Safety is more or less disregarded (e.g., no safety equipment
(many workers work in shorts with no hard hat, shirt or footwear), trees felled
into areas where other workers working, no communication between skidders and
sawyers so trees are pushed into areas the sawyers are working).
· Sawyers
appear unaware of the need for preparing escape routes prior to felling a
tree.
· A system of controls and rewards could be applied to logging
contractors, including rewards for good utilization practices or fines for poor
practices.
· Use of chokers could increase skidder productivity; more often
than not only one log is skidded at a time, with two logs being the
maximum.
· A major shift by the public sector toward enactment and
enforcement of new, stricter environmental controls appears unlikely in the near
future.
· Improvement of logging practices will occur most rapidly if
initiated by the private sector
· If only advanced planning of skid trails
and wet-weather shutdown were implemented, most of the current skidding damage
could be eliminated.
· Increased productivity and reduced maintenance and
repair costs to equipment would cover the above costs, as well as inventory
holding costs for the approximate five months of shutdown time required.
d'Oliveira, M.V.N. and E.M. Braz. 1995. Reduction of damage to tropical moist forest through planned harvesting. Commonwealth Forestry Review 74(3): 208-210.
· RIL study (previous survey, planning, climber cutting,
directional felling, careful construction of skid trails and roads).
·
Logging intensity is claimed to be 20 m3/ha in
Brazil, contracting the data shown in Table 1, which indicates intensity of 10
m3/ha.
· In RIL the number of damaged trees
(>10 cm dbh) per tree logged was 5.3 (or 0.27 m3 per m3 extracted)
or 27%.
· Maximum canopy opening was 15% (including all damage to the canopy
in felling, skid trail, road and landing construction).
· In a study of
conventional logging by Uhl and Viera (1991), damage amounted to 1.9 m3 per m3 extracted,
while the canopy opening was 3800 m2/ha vs. 1500
m2/ha in this study.
· Uhl and Viera (1991)
got 13.8% canopy opening in careful logging.
· 450 m of road (5 m wide) was
built (22.5 m/ha), 1200 m of skid trail was built (60 m/ha), and a landing of
225 m2 (25 m x 35 m) was built.
· Average
growing stock (dbh >10 cm) was 247.9 m3/ha,
or 133.9 m3/ha when dbh >50cm.
·
Marketable species volume was contained in 109 trees/ha, of which 19 were of
commercial size.
· In the 20 ha - 57 trees were felled (2.85 trees/ha) with a
total volume of 199.331 m3 (3.5 m3/tree or 10 m3/ha).
· In many parts of the tropics, forest
management has paid little attention to the minimization of damage caused to the
forest through exploitation. The main concern has been with the choice and
performance of the logging technologies and equipment employed.
· When the
subject of sustaining wood production over a number of cutting cycles is
considered, it becomes obvious that planned exploitation is the key to ensuring
that the growing stock is maintained at a desirable level.
· In addition to
sustaining timber production, it is important for the provision of other
services such as biodiversity, local climate, etc.
· Regeneration also
requires that attention be paid to the size of clearing, a factor much
influenced by the felling operation (Yared and de Souza 1993).
· Planned
production reflects positively on management costs (Hendrison 1989) - he
reported that average annual skidder production doubled with planned harvesting,
when compared to conventional harvesting.
DOSSIER: Recherches sylvicoles en Indonésie. 1999.
STREK, CIRAD-Forêt et FORDA. Bois et Forêts desTropiques. 1999. #259 (1).
5-45.
· This study was carried out in Indonesia (east Kalimantan) as part
of the STREK project.
· In this publication the application of silvicultural
treatments and reduced impact harvesting techniques were evaluated.
· In
conventional logging the minimal harvesting diameter was 60cm dbh.
· In RIL
operations the minimum harvesting diameters was 50cm and 60cm dbh
respectively.
· The following data were found for the correlation between
damage level and mortality:
|
Damage level |
Basal area remaining |
Mortality rate (%/year) |
|
Light |
> 80% |
1.6 |
|
Moderate |
70-80% |
2.4 |
|
High |
< 70% |
2.9 |
· 26% of residual stand were damaged during harvesting,
resulting in 51% of the total mortality two years after harvesting.
· The
following data show the relation between silvicultural system, mortality and
growth rate:
|
Treatment |
Mortality |
Growth rate (m3/ha/yr) |
Recruitment (m3/ha/yr) |
Mean annual increment (m3/ha/yr) |
|
Virgin Forest |
1.31 |
2.31 |
0.58 |
+1.58 |
|
Systematic Thinning |
1.32 |
4.85 |
1.37 |
+4.9 |
|
Selective Thinning |
2.08 |
4.56 |
0.63 |
+3.11 |
|
Control CL |
2.62 |
3.36 |
0.17 |
+0.91 |
|
RIL 50 |
2.15 |
3.44 |
0.34 |
+1.67 |
|
RIL 60 |
3.09 |
3.74 |
0.24 |
+0.88 |
|
CL 60 |
3.55 |
3.67 |
0.63 |
+0.75 |
Durrieu de Madron, L., Forni, E. 1997. Aménagement
forestier dans l'est du Cameroun. CIRAD-Forêt. Bois et Forêts des Tropiques. 254
(4). 39-50.
· The project API (aménagement pilote intégré) was carried out at
Dimako, Cameroon.
· Harvesting intensities greater than 1tree/ha were
recommended.
· A cutting cycle of 30 years and a planting prescription for
areas with poor regeneration were recommended.
Durrieu de Madron, L., Fontez, B., Dipapoundji, B. 2000. Dégâts d'exploitation et de débardage en fonction de l'intensité d'exploitation en forêt dense humide d'Afrique centrale. CIRAD-Forêt, Projet ECOFAC. Bois et Forêts des Tropiques. 264 (2). 57-60.
· This study was carried out in Central Africa.
· The
main objective of the "ECOFAC" project was to determine the relation between
harvesting intensity and damage to the residual stand.
· Most of the damage
was caused during skidding operations.
· The harvesting intensity ranged from
0.4 - 4 trees/ha.
· The minimum harvesting diameter was 80cm dbh, however,
few trees smaller than 90cm dbh were cut.
· The following data were found
for the relation of site damage and harvesting intensity:
|
Harvesting Intensity (trees/ha) |
Site Damage (% of total area) |
|
0.24 |
3.71 |
|
0.44 |
3.79 |
|
0.60 |
7.21 |
|
0.76 |
4.35 |
|
0.88 |
6.11 |
|
1.16 |
9.40 |
|
1.20 |
9.05 |
|
1.28 |
7.90 |
|
1.40 |
9.17 |
|
1.68 |
12.40 |
|
1.76 |
14.60 |
|
1.84 |
10.95 |
|
2.32 |
15.68 |
|
3.28 |
19.90 |
· On average 0.8% of the surface were affected by roads and landings.
Durrieu de Madron, L., Forni, E., Mekok, M. 1998. Les
techniques d'exploitation `a faible impact en forêt densehumide camerounaise.
CIRAD-Forêt. 1998. 29pp.
· This publication is based on results from
Project A.P.I. de Dimako (east Cameroon) and studies from the Ivory Coast and
Central Africa.
· The main goal of this study was to identify harvesting
techniques that minimise damage to the residual stand.
· Maximal harvesting
intensity (A.P.I. de Dimako) was increased from 0.8 trees/ha (10 m3/ha) to 3 trees/ha (40 m3/ha).
· A sufficient number of seed trees must be
retained to provide for regeneration and biodiversity.
· Approximately 25% of
the harvested volume was left behind as waste or due to oversight.
· Main
and secondary roads affect 1-2% of the total area.
· With harvesting
intensities of 0,5-1 tree/ha (5-15 m3/ha)
approximately 3% of the site is damaged during skidding operations.
·
Governments should provide economic incentives for the implementation of reduced
impact logging techniques.
Dykstra, D.P. 1992. Wood residues from timber harvesting and primary processing: a global assessment for tropical forests. Food and Agriculture Organization of the United Nations, unpublished mimeograph. 93pp.
· Estimated volume of trees left standing on harvested areas, forest residues, and felling recovery rates for the three tropical regions around 1986, with data for the U.S.A. provided for comparison sake:
|
Region |
Estimated standing volume on harvested areas |
Estimated residual volume on harvested areas |
Estimated volume felled (mill.m3) |
Estimated forest residues (mill.m3) |
Industrial roundwood production (mill.m3) |
Estimated felling recover rate (%) |
|
Africa |
251.664 |
179.587 |
72.077 |
33.512 |
38.565 |
54 |
|
Asia/Pacific |
905.822 |
669.672 |
236.150 |
127.884 |
108.266 |
46 |
|
Latin America/ Caribbean |
657.273 |
499.556 |
157.716 |
70.014 |
87.702 |
56 |
|
Total |
1 814.759 |
1 348.815 |
465.943 |
231.410 |
234.533 |
50 |
|
U.S.A. |
na |
na |
493.385 |
110.796 |
382.589 |
78 |
· Estimated sawmill recovery rates for the tree tropical regions around 1986, with data for the U.S.A. provided for comparison:
|
Region |
Sawnwood production (mill.m3) |
Estimated sawmill residues (mill.m3) |
Estimated sawmill recovery rate (%) |
|
Africa |
6.503 |
7.527 |
46 |
|
Asia/Pacific |
34.314 |
34.027 |
50 |
|
Latin America/ Caribbean |
25.424 |
34.415 |
42 |
|
Total |
66.241 |
75.969 |
47 |
|
U.S.A. |
88.065 |
122.667 |
42 |
· Estimated plywood recovery rates for the tree tropical regions around 1986, with data for the U.S.A. provided for comparison:
|
Region |
Plywood production (mill.m3) |
Estimated plywood residues (mill.m3) |
Estimated plywood recovery rate (%) |
|
Africa |
0.445 |
0.455 |
49 |
|
Asia/Pacific |
7.969 |
8.741 |
48 |
|
Latin America/ Caribbean |
1.433 |
1.801 |
44 |
|
Total |
9.847 |
10.997 |
47 |
|
U.S.A. |
22.710 |
24.522 |
48 |
· Amount of logging and mill residues generated in the
tropics was estimated to be 208 million m3
annual, or 89% of the total annual production of industrial roundwood.
·
About 60% of mill residues in tropical countries are unutilized.
· Report has
logging residues, sawmill and veneer mill residues for Cameroon, Ghana, Nigeria,
Indonesia, Malaysia, Philippines, Thailand, Brazil, Columbia and Peru.
·
Quantities and types of residues generated at each stage of the harvesting
operation (10 country average) (all volumes 1000 m3 sob):
|
Total m3 of standing timber on logged areas (TVOL) = 42150.2 |
|
|
Volume of non-utilized species = 6884.5 (16.3% of TVOL) | |
|
Volume of small-dimension trees = 1805.0 (4.3% of TVOL) | |
|
Volume of reserved commercial trees = 4518.5 (10.7% of TVOL) | |
|
Volume to be felled (VFELL) = 28942.2 |
|
|
Volume in high stumps = 1918.9 (6.6% of VFELL) | |
|
Felling breakage = 1226.2 (4.2% of VFELL) | |
|
Volume to be limbed and crosscut (VL&C) = 25797.1 |
|
|
Rejected pieces = 8454.3 (32.8% of VL&C) | |
|
Losses due to improper bucking = 361.2 (1.4% of VL&C) | |
|
Volume to be skidded (VSKID) = 16981.7 |
|
|
Skidding breakage = 263.0 (1.5% of VSKID) | |
|
Lost or rejected pieces = 413.2 (2.4% of VSKID) | |
|
Volume at landing (VLAND) = 16305.4 |
|
|
Loading losses and damage = 853.3 (5.2% of VLAND) | |
|
Volume on truck (VTRUCK) = 15452.1 |
|
|
Transport losses and damage = 124.9 (0.8% of VTRUCK) | |
|
Industrial Roundwood Volume = 15327.2 (36% of TVOL or 53% of VFELL) |
Should approximately equal IRW production as reported in the FAO Yearbook of Forest Products |
· Quantities and types of residues generated during sawnwood production (10 country average):
|
Volume scheduled for harvest (TVOL) = 42150.2 |
|
|
Timber not harvested = 13208.0 (31.3% of TVOL) | |
|
Harvesting and transport losses = 13615.0 (32.3% of TVOL) | |
|
Industrial roundwood volume (IRW) = 15327.2 |
|
|
Volume to other mills or export = 6715.2 (43.8% of IRW) | |
|
Volume at sawmills (VSMILL) = 8612.1 |
|
|
Debarker residues = 140.4 (1.6% of VSMILL) | |
|
Sawdust = 767.9 (8.9% of VSMILL) | |
|
Slabs and edgings = 1994.9 (23.2% of VSMILL) | |
|
Board end trimmings = 403.5 (4.7% of VSMILL) | |
|
Planer shavings = --- | |
|
Drying losses = --- | |
|
Unusable sawnwood = --- | |
|
Other conversion losses = 1450.8 (16.8% of VSMILL) | |
|
Volume of sawnwood production (VSAWN) = 3854.7 (44.8% of VSMILL) |
|
|
Storage and transport losses = 56.3 (1.5% of VSAWN) | |
|
Sawnwood delivered to market (VSDELIV) = 3798.4 |
|
|
Premature degradation = --- | |
|
Sawnwood in final use (VSFINAL) =3798.4 |
· Quantities and types of residues generated during plywood processing (10 country average):
|
Volume scheduled for harvest (TVOL) = 42150.2 |
|
|
Timber not harvested = 13208.0 (31.3% of TVOL) | |
|
Harvesting and transport losses = 13615.0 (32.3% of TVOL) | |
|
Industrial roundwood volume (IRW) = 15327.2 |
|
|
Volume to other mills or export = 13612.7 (88.9% of IRW) | |
|
Volume at plywood mills (VPMILL) = 1705.5 |
|
|
Debarker residues = 58.8 (3.5% of VPMILL) | |
|
Cores and lathe roundup = 197.1 (11.6% of VPMILL) | |
|
Spur knife trim = 19.3 (1.1% of VPMILL) | |
|
Veneer waste and clippings = 227.4 (13.3% of VPMILL) | |
|
Drying losses = 19.4 (1.1% of VPMILL) | |
|
Panel trimmings = 34.3 (2.0% of VPMILL) | |
|
Sander dust = 12.1 (0.7% of VPMILL) | |
|
Volume replaced in patching = -- | |
|
Other conversion losses = 301.2 (17.7% of VPMILL) | |
|
Volume of plywood produced (VPLY) = 835.9 (49.0% of VPMILL) |
|
|
Storage and transport loss = --- | |
|
Plywood delivered to market (VPDELIV) = 835.9 |
|
|
Premature degradation = --- | |
|
Plywood in final use = 835.9 |
· Harvesting operations in natural tropical forests can reduce logging residues by 10-30% without a significant increase in harvesting cost.
Dykstra, D.P. and R. Heinrich. 1992. Sustaining tropical forests through environmentally sound harvesting practices. Unasylva 43(169): 9-15.
· If tropical forests are to be retained as forest, then
for the most part their resources must be utilized. Otherwise, they risk being
perceived by local people and government decision-makers as having less value
than other land-use options.
· Improper harvesting practices can so degrade
the forest that future timber and non-timber values may be substantially
reduced.
· There is evidence that the degree of damage is increasing as
logging operations extend over more rugged terrain and become increasingly
mechanized, relying to a greater extent on "horsepower" rather than on technical
competence (Fox 1968, Nicholson 1979, Marn and Jonkers 1982).
· Sufficient
information exists to permit sustainable harvesting operations in virtually any
area of tropical forest world-wide.
· Not just preserving nature, you can
save money also through tighter operations as shown in three studies (Marn and
Jonkers 1982, Hendrison 1989, Schmitt 1989).
· Need to use the best knowledge
available in planning, forest roads, felling, skidding and yarding, and
post-harvest assessments.
· Nicholson (1958, 1979) suggests that harvest
planning for tropical forests is less now than it was during the colonial
era.
· Although harvesting planning implies an increase in initial cost, it
can help avoid many problems and costs by reducing wastage and improving
efficiency of operations (could cost 20-45% less overall).
· Improper felling
can cause damage to pole-size trees, which could be potential crop trees in the
future.
· Improper cross-cutting can cause timber wastage and loss of log
value.
· Skidders tend to wander through the forest searching for trees, thus
resulting in excessive damage to residual trees.
· Post-harvest assessment is
necessary to give valuable feedback as to the success or failure of the
harvesting operation on long-term sustainability.
Dykstra, D.P. and R. Heinrich. 1996. FAO model code of forest harvesting practice. Food and Agriculture Organization of the United Nations, Rome. 85 pp.
· Completely outlines RIL and procedure to follow.
·
Experience with training programs to improve crosscutting skills suggest that
improved utilization of 20% or more and increased log values of 10-50% can be
attained by such training.
· Although skid trails commonly represent 20-40%
of the harvesting area, several studies have found 60% or even 80% of the area
covered with skid trails after selection harvesting had been completed.
Dykstra, D.P., G.S. Kowero, A. Ofosu-Asiedu and P. Kio (eds.). 1996. Promoting stewardship of forests in the humid forest zone of anglophone West and Central Africa. The United Nations Environment Programme and The Centre for International Forestry Research, Final Report. 103pp.
· Felling cycle is defined as the period between two
successive commercial harvests in the same forest stand.
· The optimum
felling cycle is one that ensures complete forest recovery and sufficient stem
recruitment into the exploitable diameter class.
· The length of felling
cycle is directly related to logging intensity, which is also affected by
species composition, stem diameter distribution, total stocking, silvicultural
characteristics of desirable species, cost of exploitation and financial needs
of the forest owner.
· Felling cycle in Cameroon is 30-60 years.
· Felling
cycle in Nigeria is 50 years.
· Felling cycle in Ghana is 40 years.
·
Felling limits between 50-110 cm dbh are used in West Africa and vary by country
and species (table given in report).
· In south-east Asia 33% of the total
area and 33-67% of the residual trees are damaged after logging.
Elias, Ir. 1996. A case study on foret harvesting, damage, structure and composition: dynamic changes of the residual stand for dipterocarps forest in East Kalimantan, Indonesia. In: Proceedings of Forest Operations for Sustainable Forestry, XX IUFRO, World Congress, August 6-12, 1995. IUFRO S3.05-00 and CIFOR Publication. p.13-27.
· Effects of forest harvesting with the Indonesian
Selection Cutting and Planting (TPTI) system.
· Almost all the concession
holders use the TPTI system.
· Cutting cycle is 35 years and the minimum
felling dbh is 50 cm.
· Felling with chain saw and crawler tractor (160 kW)
skidding.
· Degree of residual stand damages by plots:
|
Slope, % |
Trees before logging, dbh >10 cm |
Logging intensity, trees/ha |
Percent of residuals damaged | |
|
In PT, Narkata Rimba I II III |
0-15 16-25 >25 |
620 697 748 |
2 6 17 |
9.39 21.13 35.43 |
|
In PT, Kiani Lestari I II III |
0-15 16-25 >25% |
565 487 480 |
8 9 8 |
38.60 46.20 46.82 |
· Most of the damage was in smaller trees (NR 65.23%
damaged trees with dbh 10-19 cm, and 28-33% in KL).
· 75% of the injuries
were caused by skidding and 25% by felling.
· Canopy opening size ranged from
285-512 m2/tree felled and averaged 396 m2/tree felled.
· Mortality of residual trees 10-39
cm dbh was 6-26.6% during the harvesting year, 2-13.6% one year after, and
0.7-3.6% two years after.
· Higher damage occurring in residual stands causes
the higher tree mortality.
· The mortality of trees in virgin forest was
0.9-2.4% per year (1.1% average).
· At NR the dbh growth of trees with dbh
>10 cm was initially 0.55-1.25 cm/year after logging but reduced to 0.41-1.04
cm/year.
· At NR the dbh and volume growth of 25 nucleus trees one and two
years after logging were 0.92 and 0.50 cm/year, and 1.832 and 0.901 m3/ha/year.
· At KL the average dbh growth on trees
>10 cm was 0.80-0.95 cm/year after harvesting, and 0.47-0.69 cm/year 4, 9, 13
and 17 years after harvesting; dbh growth in virgin forest is 0.51-0.74
cm/year.
· At KL the average growth of commercial trees with dbh >10 cm
was 2.97 m3/ha/year.
Elias. 1999. Introducing a manual on reduced impact timber harvesting in the Indonesian selective cutting and planting system. ITTO Tropical Forestry Update 9(3): 26-30.
· Timber harvesting in Indonesia is carried out under the selective cutting and planting system. This system is often considered to cause forest degradation.
Enright, N.J. 1978. The effects of logging on the regeneration and nutrient budget of Araucaria cunninghamii dominated tropical rainforest in Papua New Guinea. The Malaysian Forester 41(4): 303- 318.
· Initial basal area was 42.11 m2/ha of which 29.4 m2/ha was A.
cunninghamii.
· In the logging almost all A.
cunninghamii were removed (dbh >40 cm).
· Selective logging was very
destructive to all size classes of A.
cunninghamii.
· Of the 168 A. cunninghamii
individuals (dbh >10 cm), 67 were of commercial size and 64 of these were
removed.
· 60 of the remaining 101 trees were destroyed, and by 14 months
after felling four more individuals died due to damage sustained during logging
(56 remaining A. cunninghamii).
· The number of
saplings was reduced from 66 to seven, and a further four died by 18 months
after logging.
· Of the 143 individuals of non-commercial species (>10 cm
dbh) only nine survived.
· Means annual increment in the logged area was 0.71
cm/year and 0.36 cm/year, one and two years after logging.
· Mean annual
increments for the corresponding years in the undisturbed site were 0.39 cm/year
and 0.42 cm/year.
· Nitrogen and organic carbon levels were back almost to
preharvest levels within 18 months.
· Chemicals such as calcium and potassium
will take much longer to return to preharvest levels.
· Early secondary tree
species rapidly occupy the disturbed sites.
· Under the present logging
practices, even where an adequate sapling stand is available, destruction during
logging reduces the number of saplings to such an extent that development of a
commercially viable stand must start from seed germination rather than sapling
development.
· Due to the slow growth rate of A.
cunninghamii it would be preferable to regenerate the species from saplings
since the rotation age could be reduced by 100 years (i.e., eliminate 30 year
early successional stage and 50+/-20 years needed for seedlings to read 10 cm
dbh).
· Due to the severe logging damage to advance growth, it was estimated
that it would take 300 years for the stand to approach its former state due to
the slow growth rate of A. cunninghamii.
Ewel, J. and L. Conde. 1980. Potential ecological impact of increased intensity of tropical forest utilization. BIOTROP, Special Publication No. 11. 70pp.
· Thorough review of the literature on logging impacts in tropical forests with articles ranging from 1909 to 1980 (most articles from 1950 to 1980).
FAO, 1989a. Management of tropical moist forests in
Africa. Food and Agriculture Organization of the United Nations, Rome, Forestry
Paper 88. 165pp.
· Soil disturbance 20-25% of logged area.
· The TMF
of Africa have a lower stocking of commercial species than in the MDF in
south-east Asia.
· Big problem is what share of the growing stock is
merchantable, because the varies between locations and between years.
· In
the past concessionaires were obliged to plant 3 to 10 plants of the same
species for every one which they had felled - this was soon abandoned as a
failure because no proven planting technique had been developed and control of
operations scattered sparsely over thousands of hectares was impossible.
·
Forest services starting doing their enrichment plantings themselves (1930
...).
· After WWII there was a swing toward natural regeneration
(1950-60).
· Again in 1960 results of natural regeneration were judged
generally disappointing and the pendulum swung back to plantations in
francophone African countries.
· Realization that most of the valuable
species in African TMF are light demanders has led to an increasing trend
towards planting forest sites after complete removal of the pre-existing forest
(timber species on closed forest sites 1,200-2000 USD/ha, pines and eucalypts on
savannah sites 700-1000 USD/ha - 1986).
· Well planned and carefully
controlled harvesting systems are superior economically, environmentally and
silviculturally. Such harvesting systems should be fully integrated with the
management system, but has been an elusive goal in the tropics.
· Harvesting
problems in the tropics:
high rainfall - (1500-4000 mm/year) with little or no dry season, makes felling, extraction, and transport difficult. Even with a good road system, road transport may be limited to 180-220 days a year because of climate
topography - a significant part of the forests of Congo, Gabon and Zaire, as well as the montaine forests of East Africa, are found on steep slopes
difficult soils - (excessively sandy or excessively clayey) which, in conjunction with high rainfall, make logging and transport difficult
large tree sizes -
long distance to market - in some cases.
inadequate knowledge of forest - although a great part of the forests have been inventoried, the intensity of the inventory is often too low to provide acceptable information on stocking on smaller blocks of less than 20,000 ha (sometimes less than 100,000 ha).
heterogeneous composition of the forest - commercial volume varies greatly according to proximity to local markets or to ports for export, the sales policy of the concessionaire and the annual fluctuations in the market.
· Total bole volume in francophone African countries
average 111 m3/ha, of which 61 m3/ha (11.5 trees/ha) is commercial (>70 cm dbh),
and of which 15 m3/ha (2.3 trees/ha) is
commercial volume of the preferred species.
· Licenses are not linked
directly to regeneration success, therefore, there is no incentive for a
concessionaire to minimize damage to residuals and therefore ensure there is
volume for future logging operations.
· Every felled mature trees destroys
0.02-0.04 ha of forest, therefore will have some damage to residuals
irrespective of what you do.
· Controversy of polycyclic vs. monocyclic
silviculture systems - examples of both which have been adopted by
countries.
· In polycyclic - must use RIL to maintain at least 15 trees in
the 30-60 cm dbh classes, therefore assuming a 30 year felling cycle and growth
of at least 1 cm dbh per year there will be a similar volume available as in the
first cut (i.e., 15 trees with average dbh of 75 cm will equal same volume as
4-5 trees with mean dbh of 110 cm) - quality will be slightly decreased because
of a wider range of species used and smaller log size.
· There is a need for
partnership between harvesting and silviculture:
· In Uganda, the current
policy is to avoid any system that will tend to convert TMF into single species
plantations or even uniform blocks.
· The current rate of harvesting in
Nigerian moist forests is so high that almost all the valuable timber will have
been harvested by the end of the century.
· In Cote d'Ivoire, silviculture
experiments with logging intensity - by removal uncommercial species by 30-40%
of the basal area, growth of marketable species increased by 50-100% - indicate
that in 40 years they are confident that the majority of stems in the 20-40 and
40-60 cm dbh classes will move up to the next higher size classes.
FAO, 1989b. Review of forest management systems of tropical Asia. Food and Agriculture Organization of the United Nations, Rome, Forestry Paper 89. 228pp.
· Diversity of the vegetation coupled with the
complexity of socio-economic conditions have led to the evolution of a wide
spectrum of management systems. However, what is actually practiced seldom fits
into the description usually found in silviculture text books and often
represents a compromise between conflicting factors.
· Felling rules in
Kerala (no two trees within 20 m of each other may be felled/climber cutting at
time of marking to reduce felling damage/no felling 20 m on either side of a
watercourse/marking done so no lasting gaps in canopy/only dead or dying trees
marked on slopes).
· In addition all broken or completely damaged trees are
to be cut back.
· Although only a few trees are felled damage to other
standing trees is very high (e.g., if only 10 trees/ha felled, sometimes this
results in opening the canopy to the extent of 50%).
· Drastic increase in
light and change in moisture conditions encourage the growth of weeds,
especially primary colonizers, impeding the establishment and growth of
regeneration.
· Selective felling with sufficiently long cutting cycles on
moderate slopes seldom causes any erosion problems.
· Contractors (employed
by both the State (India) and private companies) are primarily interested in
profit maximization, to the neglect of silvicultural prescriptions.
·
Clearfelling adopted in India to maximize yields.
· Malaysian Selective
Management System (SMS) - based on inventory data - minimum dbh cutting limit 50
cm in dipterocarps and 45 cm in non-dipterocarps.
· Results from 100-0.4 ha
continuous inventory sample plots and another 100 experimental cutting and/or
silvicultural treatment plots (4 ha each), give following data for trees >30
cm dbh) - Malaysia:
|
Diameter growth in cm/year |
|
|
a) all marketable species |
0.80 |
|
b) dark/light and red meranti |
1.05 |
|
c) medium-heavy marketable species |
0.75 |
|
d) light non-meranti marketable species |
0.80 |
|
e) non-marketable species |
0.75 |
|
Gross volume growth in m3/ha/year |
|
|
a) all marketable species |
2.20 |
|
b) all species |
2.75 |
|
Gross volume growth % |
|
|
a) all marketable species |
2.1% |
|
b) all species |
1.9% |
|
Annual mortality % of number of marketable species |
0.9% |
|
Annual ingrowth % of marketable species growing >30 cm dbh |
0.6% |
· Preliminary studies have assessed felling damage to
remaining intermediate sized trees of >30 cm dbh to be 30%.
· Wastage due
to breakage and bucking: 6.5-8% of the gross timber volume.
· Need more
effective use of directional felling.
· In Malaysia minimum cut to be
economic estimated to be 35-40 m3/ha, with
periodic cuts every 35-40 years.
· Logging cycle in Malaysian Peninsular hill
forests could be 30 years, and the cut should be 40-45 m3/ha of currently marketable and utilizable species
(assuming 0.8-1.0 cm diameter growth per year = 2.0-2.5 m3/ha/year in commercial gross volume).
· However,
it is necessary to limit logging damage to residual stand to not more than 30%
of intermediate sized trees.
· Sabah - Modified Malaysian Uniform System
explained.
· Sarawak - Malaysian Uniform System explained.
· Philippines -
selective logging if properly implemented is still regarded as the best
silvicultural system applicable to the Philippine dipterocarp forests.
· For
1974-1983 forest destruction occurred over an average 21% of the area logged per
year, leaving an adequately stocked logged-over area of 79%.
· These forests
should yield and adequate logging volume after 30, 35, 40 or 45 years.
· In
ground-based systems 54.5% of residuals undamaged, while with high-lead yarding
43.3% undamaged.
· Could have 1-2 improvement cuts between logging cycles to
help improve the stand, cut vines, etc.
· The disappointing results of the
early attempts to transpose the Malaysian uniform system to West Africa, where
the canopy opening led more often to climber tangles than to established
regeneration, show the high degree of sensitivity to this distinction. A very
substantial jump in the uncertainty, as well as the difficulty of management is
clearly associated with systems depending on induced regeneration as compared
with release. So much so, that it could well be that the Dipterocarps are a
fortunate exception; perhaps one of the few types of the tropical mixed forest,
in which, given the present state of ecological knowledge, natural management
systems can be confidently advocated and put into effect.
· In India, the
unreliability of regeneration reinforced the trend towards plantations.
Pessimism about the prospects for the management of the tropical mixed forest
where regeneration is not readily assured might therefore be justified.
Fortunately, there are several indications to the contrary.
· Tropical
shelterwood system in West Africa lead to more often than not, to the successful
establishment of a satisfactory second crop, and that crop had all the signs of
being a more productive one than the forest it replaced.
· Uneasiness in
India, Philippines and Malaysia in regard to the low yield of the natural
tropical forest (e.g., 20 m3/ha over 30-40
years).
· Shortening the felling cycle and increasing the logging intensity
in natural tropical forests will lead to the vicious cycle of liquidation.
·
Have to careful about increased use of lesser known species to increase logging
intensity, but could be useful to decrease the demand in the same forest for the
high-value commercial species (i.e., ensure they are still available into the
future).
· This could lead to more damage and environmental impact.
·
Nicholson (1979, 1985) extremely skeptical of the chances of raising the
increment of the Dipterocarp forests to more than 2-3 m3/ha/year. The fact that after a century or more of
management in India, the average increment for the natural forests is still only
0.5 m3/ha/year.
· If all you want is wood
fibre then plantations come into question, although it is possible to grow
sawlogs and veneer logs in plantations on longer rotations (5 to 10 times
increase in increment when compared to a fully managed tropical mixed
forest).
FAO, 1991. Forest management research and development, Papua New Guinea: Project findings and recommendations. Food and Agriculture Organization of the United Nations, Rome, Project FO:DP/PNG/84/003, Terminal Report. 61pp.
· The terminal report of a series of 16 reports on
forest management, mensuration, logging operations and silviculture in PNG.
·
Although the intensity and standards of logging and log marketing vary from
company to company, there has been an increase in the number of species
harvested and number of trees harvested per hectare.
· Over 400 species are
known to have commercial value, and of these, about 70 are regularly
marketed.
· Logging is very selective with a minimum felling limit of 50 cm
dbh (59 m3/ha +/- 13.3 m3/ha), although companies dealing with export markets
maintain a 60 cm limit and the average logging intensity is 30 m3/ha (companies rarely log areas with less than 20
m3/ha).
· Potential yields are 50% greater
(i.e., 45 m3/ha) if all available commercial
species were harvested down to a 50 cm diameter, and unnecessary wastage caused
by high stumps, poor felling technique, excessive trimming and inefficient
bucking into commercial lengths were removed.
· Experience in other countries
has shown that with good control of selective logging the average commercial
wood yield expected is an average from 0.5 to 2 m3/ha/year, with a logging cycle from 20 to 40
years.
· This same experience has shown that the forest will recover after
poor logging but this adds another 10-20 years to the logging cycle due to the
loss of advanced growth required for the next cut; poor logging practices are
more likely to result in undesirable changes in species composition.
· Could
have stumpage rates by species (i.e., higher quality and larger trees have
higher stumpage rates and poorer quality trees lower stumpage rates to encourage
their use).
· Could have variable minimum dbh felling limits by species
(i.e., pioneer species can be felled at smaller dbh).
· All improvements,
stand marking, etc. require close supervision and cannot be left to the logging
contractor.
· A problem which has occurred almost everywhere where stand
improvement has been used in the tropics, is that many trees which were killed
as useless would have been marketable in the next cutting cycle if they had been
left.
· Old natural forest often seems to be saturated with basal area so
that growth ceases except in the vicinity of fallen trees. It follows that
tending must aim to keep the basal area below this saturation level and until
research determines more precisely what this level is an arbitrary figure of 30
m2/ha is a useful index to apply.
· Current
practice in most logging operations is basically very poor and the impact has
adverse effects on the sustainability of the forest resource and the stability
of the environment.
· Shortcomings are marked by a lack of adequate planning,
lack of experienced technical staff and past liberal policies in control.
·
Alignment and construction of forest roads and skid trails are very variable and
result in excessive damage to the forest; a result of a lack of adequate forward
planning and control.
· Trees are felled in the direction most convenient to
the chain saw operator and this frequently results in unnecessary damage being
caused to the tree and its neighbours.
· High stumps and bucking to a 40 cm
top results in considerable waste, with further losses in excessive trimming,
lost logs and unfelled trees of commercial quality.
· Unnecessary forest loss
occurs due to too frequent and too large log landings.
· The >30% of area
covered by roads, skid trails and landings can be reduced to <15%.
· In
each case study it was apparent that planned logging operations can effectively
reduce the area of land assigned to roads and landings.
· Skidder production
is increased in planned operations from 8.42 m3/machine hour to 12.1 m3/machine hour (43.7%).
· Better planning and
control can result in less machine time required and consequently fewer machines
required, forward marking can be practiced, and damage to the forest is reduced
with a resultant saving of residuals for the next cycle of logging and the
environment is protected.
· Maximum basal area CAI is at about 50 cm dbh,
while maximum basal area MAI increment is at about 60 to 70 cm dbh.
· The MAI
at its worst will be 0.6 m3/ha/year and best 2.5
m3/ha/year, and the logging cycle will be from
30 to 40 years.
· A felling cycle of 30 years should be used for tactical
planning and 40 years for strategic planning, as currently adopted by the
Department of Forests.
· It is also justified to use a volume increment of
between 0.8 and 1.7 m3/ha/year for predicting
future volume availability.
· Good controlled logging is the only realistic
silvicultural tool available for the management of the natural forests.
·
Planning is essential if logging operations are to be applied in an orderly
manner and damage to the forest and the environment reduced to a minimum.
FAO. 1997a. Forest harvesting in natural forest of the Republic of the Congo. Forest Harvesting Case Study # 7. Food and Agriculture Organisation of the United Nations. Rome.
· The study was carried out in a closed-canopy,
broad-leaved forest located in southern Congo at the border to Gabon.
· The
average harvesting intensity was 5.8 m3 net log
volume or approximately 1 tree/ha.
· The study inventory revealed an average
density of 455 trees/ha of which 3.3% was Okoume (Aucoumea klaineana). The felling limit was set to a
minimum of 80 cm dbh.
· The total recovery, expressed as net log volume
compared to the standing stem volume (including stump, up to the first branch of
the crown) was 70%.
· The average damage frequency was 17.7 damaged trees per
tree felled (approximately 3 trees damaged per cubic metre removed).
· The
damage rate to residual Okoume trees was 3.3% with the majority of damaged stems
in the higher dbh classes.
· Skidding damage occurred with a frequency of
11.5 trees/ha (proportion of Okoume 2.8%).
· 46% of all trees damaged during
skidding operations were fully or partly uprooted.
· The overall damage
frequency for Okoume in all diameter classes was 7.2% and for those trees 40-80
cm dbh (immature future crop trees) it was 9%.
· The damage frequency for
all species and size classes was 6.3%.
· Soil disturbance was recorded on
8.4% of the total area. Felling sites accounted for 3.8%, skid trails for 2.7%,
secondary roads for 1.0%, primary roads for 0.7% and landings for an estimated
0.2%.
· A more detailed survey shows that 0.9% of the area were seriously
disturbed by skid trails and landings (mineral soil exposed) and 5.8% of the
area were slightly disturbed by felling sites and skid trails.
· According to
a pre-harvest survey the average density of harvestable trees in the study area
was less than one tree per hectare.
· The harvestable volume (_80cm dbh) of
Okoume was 11.8 m3/ha (total volume of Okoume
37.5 m3/ha).
· The average wood recovery rate
was 86% after felling and 70% after crosscutting. The loss of 14% of the volume
during felling was due to stump wood and stem wood that does not meet the
quality requirements. The possibilities for increasing felling recovery are very
limited, since the stump wood is not considered usable.
· Assuming an average
skid trail width of 4m, the area covered by skid trails is approximately 2.7% of
the total area.
· The road and skid trail network, including landings,
covers approximately 4.6% of the total surface of the study area.
FAO. 1997b. Harvest Impacts. Forest Harvesting Bulletin 7(1): 1-4.
· Eastern Amazonia:
Three felling intensities were used where 20, 40 and 60% respectively of all trees over 40cm dbh were harvested.
The impact on the soil was examined both in dry and rainy seasons (soil moisture 39-43% and saturated respectively).
Concentrating vehicle movement on skid trails can reduce the total area of compacted soils.
The use of a smaller diameter winch line allows for an increase in the distance between skid trails.
Poorly positioned logs and communication
problems between choker setter and skidder operator were the main reason of
damage to the residual stand.
Increased traffic caused an
increase in mechanical and shear forces down to a soil depth of 20cm and a
decrease in water conductivity and air permeability.
Water conductivity and intrinsic air permeability were reduced drastically after the first pass of heavy machinery.
Signs of compaction were still found 12 years after the skidding occurred.
The position of the log after felling is directly correlated with the degree of damage caused by extraction and with operational productivity.
· East Kalitamantan, Indonesia (STREK project):
Primary and secondary mixed lowland dipterocarp forests covered the study area.
RIL techniques were applied with two diameter limits (50 and 60cm dbh respectively).
The net annual increment increased from 0.7 m3/(ha*a) to 1.3 m3/(ha*a) with the transition from conventional logging to reduced impact logging.
Logging damage to the residual stand can be reduced from 40-50% to 25-30% if several recommended improvements to conventional logging methods are implemented.
· East Kalitamantan, Indonesia:
This study analysed the impact of conventional and reduced impact wood harvesting within the Indonesian Selective Cutting and Planting System>
The following data summarise the results of the impact study:
|
Impact Results |
Method of Harvesting | |
|
Conventional |
Reduced Impact | |
|
Residual stand damage by stage of vegetation (%) - Seedlings - Saplings - Poles and trees |
33% 35% 40% |
18% 20% 19% |
|
Tree damage based on injury size (%) - Light and medium injury - Heavy injury |
12% 29% |
7% 12% |
|
Canopy opening (%) - Caused by felling - Caused by skidding |
11% 9% |
8% 5% |
· The comparison of production costs shows no significant difference between conventional and reduced impact harvesting methods.
FAO 1997c. Environmentally sound forest harvesting. Forest Harvesting Case Study # 8. Food and Agriculture Organisation of the United Nations. Rome.
· This study was carried out in the Amazon region of
Brazil, testing the applicability of the FAO Model Code
of Forest Harvesting Practice.
· The planned harvesting cycle is 25
years.
· The average harvesting intensity is 35 m3/ha with a maximum of 40 m3/ha (about half of the average harvestable volume
per hectare found for the project area).
· For the environmentally sound
forest harvesting system, 33% of the timber volume found by the commercial
inventory prior to harvesting was removed (equals 26% of the trees of commercial
interest).
· In conventional harvesting operations 73% of the timber volume
was removed (69% of the trees of commercial interest).
· Classification and
percentage of workplace time consumption:
|
Reduced impact logging |
Conventional logging | |
|
Work time |
17 h 15 min |
13 h 34 min |
|
Non-work time |
40 min |
26 min |
|
Workplace time |
17 h 55 min |
14 h 00 min |
|
Trees felled |
44 |
43 |
|
Trees only bucked |
6 |
2 |
|
Trees harvested |
50 |
45 |
|
Trees rejected |
19 |
2 |
|
Utilisable volume |
353.90 m3 |
250.81 m3 |
|
Volume/tree |
7.08 m3 |
5.57 m3 |
|
Time required for felling a single tree |
21.41 min |
17.59 min |
|
Productivity for felling |
19.76 m3/h |
17.92 m3/ha |
|
Time required for extraction of a single log |
9.27 min (pre-skidding) |
10.35 min |
|
4.27 min (skidding) |
||
|
Productivity for extraction |
31.04 m3/h (pre-skidding) |
24.90 m3/h |
|
65.53 m3/h (skidding) |
· The estimation of production costs is based on the productivity for harvesting operations as stated above. The hourly cost estimates are based upon information obtained from the company:
|
Reduced impact logging |
Conventional logging | ||
|
Actual production cost (%) |
Planned production cost (%) |
Production cost | |
|
Commercial inventory |
15 |
16 |
- |
|
Forest road |
24 |
26 |
27 |
|
Road maintenance |
6 |
7 |
- |
|
Trail pre-opening |
4 |
3 |
- |
|
Felling |
12 |
9 |
10 |
|
Pre-skidding |
29 |
28 |
- |
|
Skidding |
10 |
11 |
63 |
|
Total |
100 |
100 |
1000 |
· Referring to the costs of the conventional logging
system per cubic metre of saw log at landing site as 100%, the costs the of
environmentally sound forest harvesting system come to 109% and would amount to
101.5% of the environmentally sound forest harvesting system had been carried
out according to the planned changes.
· Severe harvesting damage to
potential crop trees was more than two times higher in the conventionally logged
unit than in the unit harvested according to RIL guidelines (In the reduced
impact harvesting operation 19.5% percent of the potential crop trees were
damaged during felling and 2.7% during skidding. In the conventional logging
operation 32.3% of the potential crop trees were damaged during felling and
19.8% during skidding).
· Two years after harvesting the plant density in
skid trails was about two times higher than in gap openings. Soil compaction did
not seem to have an influence regarding plant density.
· In the reduced
impact logging unit the area occupied by skid trials amounts to 4.2% of he total
area, whereas in the conventional logging system the affected area amounts to
18.7%.
· Measurements carried out one week after skidding indicate that soil
compaction as found after several skidder passes severely restricts the
infiltration of water into the ground.
· Dragging of heavy logs (e.g.
cableways) also considerably diminishes the infiltration rate.
· The total
timber losses amounted to 8.5% in the conventionally logged area and 3.9% in the
reduced impact logging area. Losses due to forgotten logs did not occur since
all trees had been numbered prior to harvesting.
· The most important cause
of timber loss in the reduced impact logging system was unsatisfactory
crosscutting and topping. This could have been avoided by using a measuring
tape.
· Reduced impact logging caused canopy gaps totalling 10.8% of the area
(mean size 174 m2, maximum size 532 m2), while conventional logging resulted in canopy
gaps on 24.7% of the area (mean size 150 m2,
maximum size 317 m2).
· Severe harvesting
damage to potential crop trees was found to be more than twice as high in
conventionally logged areas (51.5%) as compared to the environmentally sound
forest harvesting system (22.2%).
FAO, 1997d. State of the World's Forests: 1997. Food and Agriculture Organization of the United Nations, Rome, Italy. 200pp.
· 3 454 million ha (1995) of forest area or 26.6% of
total land area of the world (Greenland and Antarctica excepted).
· Temperate
and boreal forests 1.64 billion ha and tropical forests 1.76 billion ha.
·
Many improvements in tree-felling operations, extraction systems and forest road
construction have come about as a result of efforts to minimize the negative
environmental impacts.
· Evidence from studies done in various countries
suggests that environmentally-sound forest harvesting practice may be only
marginally more expensive than traditional methods.
· However, there are
clear economic and ecological benefits arising from the reduced damage of both
felled and residual trees, smaller areas needed for roads, skidtrails and
loading/landing areas, and reduced wood waste.
· Dykstra (1992) - of all the
wood felled annually for timber in tropical forests, about half remains in the
forest as unused wood residues.
· Need for improvements in tree-felling
operations (cutting of climbers and vines before tree felling, directional
felling).
· Recent studies on improved tree felling techniques show increased
wood volume recuperated of up to 30% and that damage to the residual forest
stand can be reduced by more than 20%.
· Low impact wood extraction systems,
better planned skid trails and forest roads, environmentally-acceptable
harvesting and forest engineering operations are gradually being adopted by
forest owners and contractors particularly, but not only, in the developed
world
· See Boulter above in regard to sawnwood.
· In the manufacture of
paper and paperboard pulp from chips and roundwood only made up 56% of the
furnish in 1994, where in 1970 it was 75% (i.e., increase use of recycled fibre,
non-wood fibres and other additives (e.g., clay)).
· Global roundwood
consumption 1994 was 3.21 billion m3 (fw 1.890
and irw 1.476 billion m3).
· Forecasted
roundwood consumption 2000 is 3.512 billion m3
(fw 1.885 and irw 1.627 billion m3).
FAO. 1998. Reduced impact timber harvesting in the tropical natural forest in Indonesia. Forest Harvesting Case Study # 11. Food and Agriculture Organisation of the United Nations, Rome.
· The study was carried out in East Kalimantan and
compares conventional and reduced impact timber harvesting within the Indonesian
Selective Cutting and Planting system.
· The objective of the study was to
test the applicability of the FAO model code of forest
harvesting practice 1996.
· The cutting cycle was set at 35 years.
·
Productivity of felling in conventional and reduced impact timber
harvesting:
|
Average dbh (cm) |
Volume per tree (m3) |
Time required (min/tree) |
Productivity (m3/h) | |
|
Conventional harvesting |
68.42 |
4.00 |
16.9 |
14.20 |
|
Reduced impact harvesting |
61.58 |
3.69 |
18.0 |
12.30 |
· Productivity of skidding in conventional and reduced impact timber harvesting:
|
Volume per load (m3) |
Time required per trip (minutes) |
Productivity (m3/h) | |
|
Conventional harvesting |
4.11 |
38.14 |
6.47 |
|
Reduced impact harvesting |
4.03 |
33.01 |
7.33 |
· Performance was about 100m3/h for bucking, 15 m3/h for debarking and 72- 76 m3/h for loading (conventional harvesting).
· The
productivity of skidding in reduced impact harvesting is about 13% higher than
in conventional timber harvesting.
· The total cost of timber harvesting in
conventional logging operations is 2.94 US$/m3,
while in reduced impact timber harvesting it is 2.97 US$/m3 (this does not include the topographic maps and
timber harvesting planning costs).
· Assuming a profit ratio of 30%, the
timber damages value caused by conventional timber harvesting is twice greater
than the timber damages value caused by reduced impact timber harvesting (2.94
US$/ha : 1.29 US$/ha).
· The size of the opened areas caused by felling of
one tree in conventional logging is 300m2 and in
reduced impact logging it is 212.9 m2.
· With
a harvesting intensity of 3-4 trees/ha, the opened areas caused by felling in
conventional timber harvesting is 11.10% and in reduced impact logging is
7.65%.
· With a harvesting intensity of 3-4 trees/ha, the opened areas caused
by skidding in conventional timber harvesting is 8.73% and in reduced impact
logging is 5.21%.
· With a harvesting intensity of 3-4 trees/ha reduced
impact logging can diminish by up to 35% the opened area otherwise caused by
conventional timber harvesting.
· As compared to conventional timber
harvesting, reduced impact logging can lessen damage up to 50% - without a
significant productivity decrease- through a series of timber harvest plans and
techniques, such as: cutting of vines, directional felling, skid trail planning
and construction and proper skidding.
FAO. 1999. Environmentally sound forest infrastructure development and harvesting in Bhutan. Forest Harvesting Case Study # 12. Food and Agriculture Organisation of the United Nations. Rome.
· This study was carried out in natural forests of the
Himalayan range in Buthan, focussing on "Environmentally Friendly Forest
Engineering".
· A productivity of 3.88 m3/h
was found for cable logging applying the traditional clear felling practice. The
corresponding figure for the group selection felling system was 5.01 m3/h.
· The costs per cubic metre of timber
extracted by long-distance cable crane amounts to US$ 25.53/m3 for the traditional system and US$ 20.13/m3 for the group selection system.
· The
production rates for road construction were 6.72 m/h for construction by
excavator and 15.19 m/h for construction by bulldozer.
· The total costs were
US$ 9.28/m for excavator construction and US$ 6.07/m for bulldozer
construction.
· Focussing on environmental impacts of road construction, the
superiority of the excavator technique in difficult and/or steep terrain over
bulldozer construction techniques becomes obvious, although the short-term
benefits might favour the use of bulldozers.
FAO Regional Office for Asia and the Pacific, Regional Wood Energy Development Programme in Asia. 1998. Carbon dioxide offset investment in the Asia-Pacific forestry sector: opportunities and constraints. RAP Publication 1998/9, RWEDP Field Document No. 53. Food and Agriculture Organisation of the United Nations. Bankok, Thailand.
· There is an increasing interest in using carbon offset
financing to carry out more environmentally sound forest management.
·
Conventional logging practices release large volume of greenhouse gases through
the rapid decay of trees and other vegetation and soils damaged or disturbed
during logging operations.
· Putz and Pinard (1995) suggest that
conventional logging operations damage up to 70% of the residual trees in
harvesting areas.
· Reduced impact logging is an attractive carbon offset
option because 50% of the green-house-gas-benefits are realised over the first
few years.
· A basic attraction of RIL, particularly for governments, is
that forests continue to provide economic potential through timber production
while improving the environmental value.
· RIL techniques are cost intensive.
If paid for with carbon offset money the implementation must be closely
monitored. RIL provides little monetary incentives for forest concessionaires to
invest in these techniques.
· Indonesia: In the lowland dipterocarp forest
of East Kalimantan, RIL will be introduced on 600ha. It is estimated that
logging damage to the remaining biomass can be reduced by as much as 50% through
vine cutting, directional felling, proper construction of skid trails and
carefully planned extraction. Project developers believe this project will
generate savings of 56,400 tons of carbon over its projected 40-year period.
Without outside financing the incentive to expend resources on improved
management is minimal. A carbon investment would provide training as well as pay
for various RIL activities.
· Malaysia: After a pilot stage of 3 years which
covered an area of 1400 ha, the calculated greenhouse-gas-benefits were
sufficiently positive to warrant the concession for implementing reduced impact
logging on up to 9000 ha over the coming three years. The approximate cost,
based on greenhouse gas savings, is around US$ 1.40 per ton of CO2.
Fearnside, P.M. 1989. Forest management in Amazonia: the need for new criteria in evaluating development options. Forest Ecology and Management 27(1): 61-79.
· Sustained management of Amazonian forest is
non-existent on a commercial scale and is in its infancy as a research
front.
· The low priority that has been given to developing and implementing
sustainable systems is a reflection of the low weight given to future costs and
benefits in presently-used economic calculations.
· Problems include the lack
of connection between discount rates applied to future returns and the
biological rates limiting forest growth, inappropriate accounting for
environmental and social factors and common property effects.
· When standard
discount rates (i.e., 10%/year) are compared with returns from the forestry
sector (in the order of 3%/year), the forest is sacrificed for unsustainable
uses with higher short-term returns.
· Ways of shifting the balance toward
sustainable management include:
use of a lower discount rate for judging forestry projects.
adjust present value calculations to correct for expected increases in the value of forestry products relative to other commodities.
increasing the weight given to future costs.
using shadow prices in the calculations to reflect forestry's social benefits.
assigning additional weight to irreversible costs such as species extinction.
· Lists a number of cases where good forest management
practices in the tropics have been thwarted due to political instability or
other reasons.
· Government agencies give virtually universal endorsement to
the goal of sustained forest management but do not match these ideals through
budgetary allocations or other concrete actions.
· Logging operators make no
effort to determine sustainable use intensities or to restrict their activities
to such limits. Although frequently decried as `irrational', this behaviour is
in fact quite logical under the current system of economic decision rules.
·
Rapid discounting of future returns leads to decisions to harvest natural
populations at unsustainable rates, leading to elimination of populations and
the extinction of species when the discount rate is more than twice the maximum
reproductive potential of the population.
· Another problem is known as the
`common resource dilemma', the `prisoner's dilemma' and the `tragedy of the
commons', where independent nations, firms and individuals harvest a population
as quickly as possible, although knowingly destroying the resource because each
perceives that the others will do so anyway.
· Applying NPV is often flawed
by less-than-full weight being applied to risk and uncertainty.
· Sustainable
forest management should be most attractive to large firms, since the principal
attraction of this land use is its offer of long-range stability rather than
quick profits.
· The large areas required to guarantee an adequate harvest
rotation also make big operations most appropriate.
· Individuals can however
join together to form co-operatives of sufficient size, given the proper
institutional support.
Fearnside, T. 1995. Australian hardwood logging and the sustainable harvesting of tropical rainforest. Commonwealth Forestry Review 74(3): 204-207.
· As in other developed countries, the factors which are
shaping logging practices in Australia include new government policies, economic
considerations, technical and organizational changes, and a greater awareness of
environmental factors at all levels of the community, not least the `green
movement'.
· In the coastal tropics the major disturbance is by wind and
cyclones.
· If openings in these forests are too large, they become invaded
by creepers or pioneer species of little timber value.
· Need planning,
marking of trees and directional felling.
· Helped in Australia with new GIS
and GPS technology to mark trees on maps of scale 1:10000.
· Also been
benefits of these technologies in Fiji, however, these resources are rarely
available in developing countries.
· Also a problem of using GPS in a closed
canopy tropical rain forest.
· Need a broad, not necessarily a detailed,
understanding of the ways in which the forests regenerate after natural
disturbance.
· Need clear prescriptions for the country and forest in
question.
· Need sound planning and management of logging operations.
·
All stakeholders must be environmentally aware.
Fickinger, H. 1992. Zur Verjungung einiger Wirtschaftsbaumarten in selecktiv genutzten Feuchtwaldern der Republik Kongo (Regeneration of some commercial tree species in selectively logged rain forests in the Congo). Gottinger Beitrage zur Land und Forstwirtschaft in den Tropen und Subtropen, No. 75. 226pp.
· Removed 1-2 trees/ha (=10-15 m3/ha, dbh>80 cm) on a 30-35 year cycle.
· The
selective logging did not induce regeneration of three (commercial?) species in
the gaps and involved a loss of biodiversity.
· Accordingly, any form of
utilization that relies on natural regeneration must be based on a wider range
of species, and measures must be taken in the interval between the logging
operations so as to establish adequate regeneration and concentrate increment on
the commercial species.
· Expected rotation age for individual trees is 100
years for a dbh from 70-80 cm.
Fox, J.E.D. 1968. Logging damage and the influence of climber cutting prior to logging in the lowland dipterocarp forest of Sabah. Malaysian Forester 31(4): 326-347.
· The levels of damage have increased over time and not
merely due to increased basal areas being extracted.
· This damage is of
concern as it will obviously mitigate against any attempts at selection working
or of reducing the period of time between harvests.
· Some control of tractor
working is essential if damage is to be reduced.
· When climbers were cut,
42.5% of residuals had little or no damage; with no climber cutting 26.1% had
little or no damage (logged 1966), but results from 1958 showed 55% with little
or no damage.
· Volumes extracted in treated in ft3/acre (1752, 1780, 1788,
912, 1538, avg = 1554).
· Volumes extracted in controls in ft3/acre (2164,
1435, 1891, 3008, 2004, avg = 2100).
· Considerable seedling loss due to
tractor movement and approximately 43% of the sampled squares were damaged by
machinery.
Fox, J.E.D. 1968. Defect, damage and wastage. Malaysian Forester 31(3): 157-164.
· Considerable quantities of timber are at present left
in the forests of Sabah.
· Due to difficulties of marketing little known or
uncommon, or small-sized species, considerable quantity of defective wood either
through insects or decay, and a large proportion is lost through damage in
falling, as top or bottom pieces bucked off or, less often, as bent pieces.
·
Generally logging intensity is 89 m3/ha, though
stands may reach 267 m3/ha.
· 80% of more of
the stand over 60 cm dbh is generally dipterocarps.
· The top diameter is 48
cm, but sometimes smaller material is removed (though will be hard to
sell).
· No attempt is made to extract logs that have split on felling or
cross-cutting.
· After harvesting there should be 40 +/- 9.4 dipterocarp
trees/ha of 10-50 cm dbh left as residuals.
· Only 33.6% of the residuals had
little or no damage, while 53.5% were fallen or broken off, and 12.9% had major
crown and/or bark damage.
· Of 42.5 potential dipterocarp residual crop
trees/ha in the study area, only 14.3 trees/ha had little or no damage.
· It
is generally accepted by progressive companies in Sabah that felling near the
ground tends to reduce damage due to falling: i.e., shatter, splitting, broken
logs, torn bases.
· For trees felled at 7 ft or more 50% were damaged
significantly or severely.
· For trees felled at 6 ft or less 21% were
damaged significantly or severely.
· However, a review of the information
presented indicates that not much weight can be given to the above trend (i.e.,
125 trees <= 6 ft felling height vs. 12 trees >=7 ft felling height).
Fredericksen, T.S. 2000. Limitations of low-intensity selection and selective logging for sustainable tropical forestry. Commonwealth Forestry Review 77(4): 262-266.
· In selection systems, individual trees are selected
for harvesting with the intention of maintaining sustained yield. In contrast,
selective harvesting involves cutting trees based on economic considerations of
stem size and/or quality without respect to sustained yield.
· Van Gadingen
(1998) observed an absence of regeneration of dipterocarp seedlings on sites
with soils disturbed by logging and in large logging gaps.
· It may be
preferable to reduce the rate at which new areas are logged by practising more
intensive logging in areas currently being harvested.
· Findings by Lugo
(1995) indicate that tropical forests are surprisingly resilient to disturbances
on a much larger scale than those created by single treefalls.
Gajaseni, J. and C.F. Jordan. 1990. Decline of teak
yield in northern Thailand: effects of logging on forest structure. Biotropica
22(2): 114-118.
· Selective harvest of teak reduces the volume of trees
>60 cm dbh from 100.7 m3/ha to 9.5 m3/ha (91.2 m3/ha).
· A study of a teak forest 25 years after
logging showed good regeneration of teak but a lack of large trees, especially
in the 40-45 cm dbh class, is most likely due to the harvest being too intense
and greater than can be sustained by the natural productivity of the
forest.
· In the study area 49 of 89 stumps/ha were less than 60 cm dbh
class.
· Total stem volume in stand 152.1 m3/ha (111.4 m3/ha of
teak).
· Volume removed in cut based on number and diameters of stumps
estimated at 159.5 m3/ha (89 stumps/ha).
·
The average stump height in the area was 95 cm.
· Minimum dbh cutting limit
for teak is 60 cm.
· Only 5 residual trees/ha had a dbh >60 cm.
· The
annual dbh increment for teak in the study area was 1.61 cm.
· Therefore,
another 14.25 years needed for the trees in the 35-40 cm dbh class to become
marketable (i.e., total time from previous harvest about 40 years).
Ganzhorn, J.U., A.W. Ganzhorn, J.P. Abraham, L. Andriamanarivo and A. Ramananjatovo. 1990. The impact of selective logging on forest structure and tenrec populations in western Madagascar. Oecologia 84(1): 126-133.
· Logging intensity 10 m3/ha.
van Gardingen, P-R., Clearwater, M.J., Nifinluri, T.,
Effendi, R. Rusmantoro, W. Noor, M., Mason, A., Ingleby, K. and Munro, R.C.
1998. Impacts of logging on the regeneration of lowland dipterocarp forest in
Indonesia. Commonwealth Forestry Review 77(2):
71-82.
· The study was conducted in Central Kalimantan (Indonesia) in
lowland dipterocarp forest. Annual rainfall is high (3500mm) with a drier season
from July to October.
· The forest is dominated by members of the
Dipterocarpaceae (17% of total number, 40% of basal area) and Euphorbiaceae (15%
of total number, 6% of basal area).
· The average stocking density is 583
stems/ha with a basal area of 34.4 m2/ha.
·
Four scenarios were evaluated: Primary forest, manual extraction (clearfelling,
processing on site, no machinery on site), conventional logging (10 trees/ha
removed) and reduced impact logging (following the FAO model code for forest
harvesting practice).
· Canopy cover in unlogged primary forest was
uniformly high; dipterocarp seedlings were present on most of the area.
·
With conventional logging, 38% of the canopy was completely removed, and logging
debris or skid trails covered 52% of the area. Dipterocarp seedlings were
concentrated along the margins of skid trails and felling gaps in areas with
undisturbed soil and partially open canopy.
· There could be significant
reductions in the level of canopy disturbance if directional felling techniques
were implemented (the gap size opened by the felling of two trees ranged from
545 m2 to 1081 m2).
· 6 months after logging, dipterocarp
seedlings were already growing rapidly in disturbed areas. The average seedling
height was higher than in areas with undisturbed canopy.
· 18 months after
logging, the tallest seedlings of pioneer species were higher than the
dipterocarp seedlings.
· Dipterocarps appear to be highly dependent upon
their mycorrhizas. Poor growth and survival of naturally regenerating
dipterocarps in logged forest could be the result of the removal of host- or
site-specific mycorrhizal fungi.
· Soil disturbance is usually minimal in
natural canopy gaps. As a consequence, the large reservoir of ectomycorrhizal
fungi within the soil and on the roots of mature trees remains largely
undamaged. Dipterocarp seedlings will thus be able to quickly gain access to a
wider diversity of mycorrhizal fungi.
· The lowest intensity of damage was
observed when timber was manually removed form the site. After 9 months the
largest seedlings were located where the canopy had been fully opened up and
where, as a result, levels of mycorrhizal infection of 74% were achieved.
·
The highest intensity of damage was observed in plots logged with conventional
techniques. Seedlings only reached mycorrhizal infection rates of 30%.
· In
primary forests (closed canopy) and natural canopy gaps infection rates of 15%
and 85% respectively were recorded.
· Both the removal of mature trees and
resulting soil disturbance are thought to severely limit the successful
establishment of dipterocarp seedlings through their apparent impact on the
mycorrhizal flora (Smits 1983).
· Data from conventional logging trials
showed that seedlings were absent on 49% of the area while the soil was
disturbed on 68% of the area.
· Although RIL is an improvement when compared
to other logging techniques, it still leads to a reduction in both the amount of
mycorrhizal inoculum available and the mycorrhizal diversity. This could affect
the regeneration of particular, perhaps commercially important, dipterocarps.
Therefore fine-tuning of this system may be required in order to ensure adequate
regeneration.
· The mean canopy opening per felled tree is 390m2.
· The optimum disturbance regime for the
processes of seedlings establishment and regeneration will be associated with
small gaps (<650m2) created by logging and
extraction of no more than 2 trees per gap. Larger gaps (>1000m2) may eventually inhibit regeneration of the forest
either through failure of seedlings to establish or through the intense
competition with pioneer species.
Gerwing, J.J., J.S. Johns and E. Vidal. 1996. Reducing waste during logging and log processing: forest conservation in eastern Amazonia. Unasylva 47(187): 17-25.
· A close look at the growth of the region's (Para
State) wood industry reveals a repeated pattern of the careless exploitation and
degradation of forests near mill centres.
· Woodwaste and increased canopy
openings result in increased fire risk.
· Breaking this destructive pattern
requires a shifting from forest mining to a system of forest management.
·
Planned forest extracting included the following pre-harvesting activities:
stand inventorying and mapping; vine cutting; road and skid trail planning and
marking. In logging, directional felling and a skidder with winch (rather than
bulldozer with no winch) were used.
· In the study found wood waste as logs
felled and bucked but never skidded, and the needless destruction of young trees
of commercial species.
· Mill waste also high through degradation of logs
before processing and excessive lumber thickness due to excessive sawing
variation.
· Waste could be greatly reduced by the adoption of
straightforward management practices.
· Traditional timber extraction
currently practiced can be thought of as unplanned forest mining that both
wastes usable timber and damages the future productive capacity of the
forest.
· The chain sawyers have little formal training in tree felling and
no training in forest management or silviculture. Payment is based on production
and not quality, thus, rapid sawing is better rewarded than careful sawing.
·
Skidding occurs several days after felling and there is no real communication
between the felling crew and the skidding crew. To find felled trees the
bulldozer operators drive their tractors towards openings in the forest canopy.
When a log is found it is skidded back to log landing, but not necessarily by
retracing the path used to arrive at the log. The result of this unplanned
searching and skidding is a criss-crossing network of skid trails, some of which
lead to natural forest gaps in which no timber tree was felled.
· In three previously logged sites 6.6 m3/ha of usable timber was felled but never skidded,
which represents one tree per hectare or as much as 20% of the 30 m3/ha of timber volume that is extracted from a
typical hectare.
· The majority of the trees found were buried under the
crowns of other felled trees or isolated from other timber trees.
· The above
type of waste did not occur in the planning logging areas.
· Other waste was
in high stumps (trees without buttresses), or not sawing the buttress off and
then felling the tree (trees with buttresses).
· Improper sawing at the base
of the tree so that the bole splits upwards from the base as it falls.
·
Bucking a tree too far from the top and leaving the usable bole with the
crown.
· In conventional logging sites it was found that 0.41 m3/tree was lost in the above four types of cutting
errors. This is 7% of the harvestable volume of a tree or 2.3 m3/ha.
· A study of 164 trees directionally felled
by a trained chain sawyer showed 0.11 m3 of
waste per tree felled in felling and bucking operations or 1.7 m3/ha less wastage.
· Combined with trees that are
never found in skidding results in a saving of 8.3 m3/ha which resulted from planned timber extraction
and training the chain sawyer.
· In conventional logging 5-6 trees/ha are
extracted, but an additional 200 trees/ha with more than 10-cm dbh are
incidentally damaged.
· Vines in the region connect the canopy of a tree on
average to six others.
· Also with uncontrolled felling the trees are often
felled on each other, cause a major tangle which the bulldozer operator must
push apart by using his blade and excessive tractor movement in the stand.
· Long lengths are generally skidded (i.e., bole is just
topped) and skidding the logs back along twisting trails results in considerable
residual tree damage and damage to the log itself.
· To reduce damage it is
proposed that: vine cutting occur two years prior to logging; directional
felling be used; planning of skid trail location; and use a tractor with a
winch.
· In conventional logging 28.7 trees (dbh >10cm) were damaged per
tree felled, compared to 20.5 trees per tree in the planned operation (46 more
trees (dbh >10 cm) were undamaged in the planned harvesting area).
· In
conventional skidding an additional 7.1 trees were damaged for each log skidded,
compared to 4.4 trees per log skidded in the planned logging. This is equivalent
to 16.2 fewer trees damaged per ha, for a total of 91 fewer trees damaged per
hectare in the planned logging areas.
· Of the 91 potential trees - 57 would
be severely damaged (i.e., topped or smashed) and of these, 11 trees (totally
2.7 m3/ha) were of species with current
commercial value.
· Processing yield at the mills in Paragominas were low
also.
· Saw timber yield was 35% (low yield due to wood waste at various
steps during log processing, inadequate log storage resulting in volume and
quality losses, excessive storage period length (i.e., 15% of log volume was
found to be affected by insect damage).
· Also log splitting (checking due to
drying) affected 13% of the total sawable log volume.
· Outdated technology
used in the sawmills (mean age 10 years) ??? result in a sawing loss of 3-5% due
to sawing thickness variation.
· Improvement should raise conversion
efficiency of veneer mills from 39% to 60% and for sawmills from 35% to
50%.
· Conventional logging gives 30 m3/ha @
35% lumber recovery or 10.5 m3/ha of lumber,
while planned logging and more efficient processing gives 38.3 m3/ha @ 50% lumber recovery or 19.2 m3/ha of lumber.
Gilmour, D.A., 1977. Logging and the environment, with particular reference to soil and stream protection in tropical rainforest situations. In: Guidelines for watershed management. Food and Agriculture Organization of the United Nations, Rome, Conservation Guide 1. p.223-235
· Ground skidding with a tractor without an arch causes
unnecessary soil disturbance and gouging of skid trails, frequently turning them
into well defined waterways which are difficult to drain - the use of an arch
would assist in reducing this sort of damage.
· It is important that road and
skid trail grades be kept as low as possible, because the erosion potential of
surface runoff increases with velocity.
· Ensuring drainage of skid trails
and roads is a self evident method of reducing erosion and stream
sedimentation.
· Uphill skidding is preferable to downhill skidding in regard
to erosion control.
· After logging the area should be inspected and roads
and skid trails put "to bed".
de Graaf, N.R., Poels, R.L.H. and van Rompaey, R.S.A.R. 1999. Effect of silvicultural treatment on growth and mortality of rainforest in Surinam over long periods. Forest Ecology and Management 124: 123-135
· These silvicultural experiments were carried out in
Surinam over a period of 30 years.
· With an initial thinning of
non-commercial species from 20 to 6-10 m2 of
basal area, the large-scale field trial had grown enough volume for a harvest of
20-30 m3/ha after 20 years.
· Harvesting of a
considerable volume per hectare might have a similar effect of release as
removing competitors around potential crop trees.
· Intensive harvesting is
usually more destructive for the residual stand per unit of basal area removed
than a silvicultural treatment in which trees area killed standing by means of
girdling.
· The results indicate that in lightly exploited forest, the
optimum schedule might be to refine or liberate heavily three times during a
cycle of 20-25 years.
de Graaf, N.R. 2000. Reduced impact logging as part of the domestication of neotropical rainforest. International Forestry Review 2(1): 40-44.
· Applying RIL for production of marketable timber
without any further steering of forest development will probably result in a
steady decrease in standing volumes of timber of marketable species.
· Under
the CELOS Silvicultural System a felling cycle of 20-30 years is applied to
previously exploited neotropical rainforest. The forest should have been
exploited under the CELOS Harvesting system, which can be classified as a
reduced impact logging system.
· The maximum harvesting intensity is 30 m3/ha. Following the harvest valuable trees have to be
released with three consecutive thinnings.
· The cost per m3of standing roundwood produced is in the order of
half a man-day.
· In Brazil (Amazonas Region) the CELOS results were applied
to an area of 80,000 ha. Soils were very poor kaolinitic clays. Drainage under
undisturbed forest was reasonable, but the soil was compacted easily.
· The
total basal area was 30 m2/ha. The maximum
harvesting level was set to 30 m3/ha on a 25
year cutting cycle.
· Harvesting activities were concentrated on trees with
a dbh preferably larger than 60cm.
· It is estimated that about 5% of the
area is compacted by machines, mostly as permanent infrastructure (skidding
trails, log landings, truck roads).
· Because of the extreme nutrient poverty
of the soil the extraction has to be restricted to timber logs in order to
minimise nutrient exports.
· Where forest management proceeds towards
classical selection felling in succeeding cycles, the frequency of harvesting
may be increased to 10 or even 5 years, with a correspondingly low volume taken
per ha. The reason is that an annual mortality of 2% eliminates too much
potentially utilisable timber over 20-30 year long cycles.
Gray, J.A., 1997. Underpricing and overexploitation of tropical forests: forest pricing in the management, conservation and preservation of tropical forests. Journal of Sustainable Forestry 4(1/2): 75-97.
· Low forest revenues can result either from low forest
fees, set at levels well below the value of the timber, or from low collection
rates, the result of inefficient collection systems.
· Low forest fees, which
mean that timber is underpriced, encourage poor utilisation of timber in the
forest and inefficiency in utilisation in processing industries.
· Economic
incentives and better-designed forest revenue systems can contribute to and
support improved forest management and administration. Higher prices and values
of tropical timber would make improved forest management economically
attractive.
Grieser-Johns, A. 1996. Bird population persistence in Sabahan logging concessions. Biological Conservation 75 (1): 3-10.
· Logging intensity in Sabah averages around 120 m3/ha.
· Logging intensity in Sarawak averages
around 90 m3/ha.
· Logging intensity in
Peninsular Malaysia averages around 52 m3/ha.
· Levels of damage of the forest are
correspondingly high.
· In the Ulu Segama Forest Reserve in south-east Sabah
the logging intensity between 1970-1990 averaged 118 m3/ha (range 73-166 m3/ha) (Marsh and Greer 1992).
· In coupes logged
during the late 1980s, tree losses during felling reached 62%, under
conventional (tractor) logging techniques, and 80% under overhead cable
techniques.
· Study emphasizes the importance of small refuge areas within
logging concessions in assisting bird recolonization.
Grieser-Johns, A. 1997. Studies on the effects of tropical forest management on biodiversity: a summary bibliography. FRR Technical Report Series No. 2. 26pp.
· A review of the literature on the effects of forest management and logging on biodiversity in the tropical and sub-tropical regions by countries/regions.
Gullison, R.E. and J.J. Hardner. 1993. The effects of
road design and harvesting intensity on forest damage caused by selective
logging; empirical results and a simulation model from Bosque Chimanes, Bolivia.
Forest Ecology and Management 59(1): 1-14.
· The value of previously
logged forests for future timber production, and the contributions of these
forests to the conservation of biodiversity, will depend to a large degree on
how much damage is done to the forest during the initial log extraction.
· In
the study area a 20-year first pass through the area is planned, with the hope
that more species can be harvested in the second harvest since the volume of
mahogany will be considerably lower (currently mahogany makes up 95% of the
harvest).
· Study area was 602 ha, from which 74 commercial mahogany trees
were extracted (= 0.12 trees/ha); the main road was 4993 m in length and 6.62 m
wide; skid trails totaled 8523 m and 3.53 m wide.
· Area under roads was 6.31
ha or 1.05%.
· Felling gaps ranged from 100 m2 to 1000 m2, with
the average size being 380 m2, resulting a total
felling area damaged of 2.81 ha or 0.47%.
· Secondary damage caused by roads
was much greater than damage caused by felling of commercial trees, with the
damage corridor being almost four times wider than the road itself (i.e., 24.69
m for main roads and 13.23 m for skid trails).
· Area of road secondary
damage was 17.29 ha or 2.87% of the total area.
· Total damage in area
directly under roads, secondary damage and gaps is 26.41 ha or 4.39% of the
study site (3569 m2/tree removed).
·
Minimizing the amount of main road minimized the amount of damage.
· The
roads built by the logging company caused 25.2% more damage than the best road
system designed by the computer program (i.e., straight main road with skid
trail running off of it).
· A computer model showed that damage to vegetation
adjacent to skid trails and damage caused by tree felling became increasingly
important components of overall forest damage as the density of harvested trees
increased, and damage to the forest rapidly escalated with increased logging
intensity.
· On the other hand more disturbance is necessary to get
sufficient regeneration of mahogany.
· Through the design of roads and the
control of harvest intensity, a forest manager can have a substantial impact on
forest damage, re-entry time and post-harvest regeneration in logged
forests.
Gullison, R.E., Hardner, J.J. 1997. The percentage utilization of felled mahogany trees in the chimanes forest, Beni, Bolivia. Journal of Tropical Forest Science 10(1): 94-100.
· The study took place in the Bolivian lowlands. Two
forest types in the Chimanes Forest contain significant quantities of mahogany
(total volume 159-180 m3/ha and 100 m3/ha respectively).
· Harvesting is regulated
through a minimum cutting diameter limit of 80cm, and the requirement that 10%
of commercial sized trees should be left as seed trees.
· The processing
efficiency at the mill is estimated as 60%.
· Wood waste was calculated
including straight branches with a minimum diameter of 20cm and a minimum length
of 1m.
· Quantities of residual branch wood are substantial, ranging from
0.85 m3 to more than 16.3 m3 per tree. In a few cases, the branch segments
themselves exceeded the minimum cutting diameter of 80cm.
· The percentage
utilisation of mahogany ranged from 49.2 to 90.5%, and decreased significantly
with increasing diameter.
· Using an average diameter of 1.3m, the
concessionaire extracts 14.48 m3 of wood per
tree felled, leaving 8.44 m3 of branch wood
behind.
· Stem cut-offs, buttresses and the stump usually account for 20.2%
of the total tree volume.
Hammond, D.S., van der Hout, P., Roderick, J.Z.,
Marshall, G., Evans, J. and Cassells, D.S. 2000. Benefits, bottlenecks and
uncertainties in the pantropical implementation of reduced impact logging
techniques. International Forestry Review 2(1):
45-53.
· While most studies suggest that there is generally an overall
net benefit in using RIL techniques, a number of uncertainties and potential
bottlenecks remain.
· The use of RIL techniques will ultimately fail to
produce the expected benefits when harvesting levels overshadow the gains made
through careful planning. Harvesting intensities are highly sensitive to the
spatial distribution of commercial stems and the ecological and economic
implementations their distribution has for reducing damage at the expense of
foregone timber.
· Stable supplies of currently marketed timber species will
only be enhanced in stands where RIL techniques are employed if the resulting
level of disturbance is consistent with the regeneration requirements of the
target timber species.
· Benefits derived from a reduction in soil
disturbance and erosion will vary depending on the prevailing background
conditions. Differences in topographical, soil and hydrological conditions will
alter the savings made by RIL when the costs of these environmental impacts are
counted.
· The interaction between slope, soil and stem size will constrain
the achievable environmental benefits without further technological and
financial inputs.
· Damage associated with the type of machinery used to
extract timber, not the way in which it is used, is limiting when conditions
prevent the use of less destructive techniques.
· It is necessary to account
for the varying cost of training and subsequent rise in wages. However, higher
wages can be seen as a medium to long-term investment.
· The capital costs
of equipment required for the implementation of RIL (such as databases, GPSs and
data loggers) must be incorporated into the calculation of costs and benefits
associated with better planning.
· If the costs of implementing RIL are at a
level acceptable to the industry, then RIL will be widely adopted.
·
Mechanisms to reduce the financial burden should be developed particularly where
financial benefits are not certain.
Hamzah, Z. 1978. Some observations on the effects of mechanical logging on regeneration, soil and hydrological conditions in East Kalimantan. BIOTROP Special Publication 3: 73-78.
· On average the standing volume (dbh >50cm) is 115
m3/ha (68 m3/ha
dipterocarps; 24 m3/ha non-dipterocarps; 23
m3/ha non-commercial).
· Based on cruise data
an estimated exportable volume is 48.5 m3/ha.
· Forestry Service in Indonesia accepts a
waste of 30%.
· Using a waste rate of 30% the net extracted volume is 34
m3/ha.
· In a review of logged over areas
very few, if any, dipterocarp saw log sized trees, poles and saplings were found
in the trafficked part of a logged-over forest.
· 42 m/ha of road to log an
area and daylighting area can extend to 50 m from the centre-line of the road on
both sides of the road.
· It is too optimistic to assume that trees of sawlog
size will mature 35 years after logging and that they will constitute the second
crop in the following cutting cycle.
Hawthorne, W.D. 1997. Towards an improved logging system
in Ghana: a fresh look at logging damage and forest regeneration (draft). FRR
Technical Report Series, No. 3. 43pp.
· a literature review on the
topic
· a literature review of logging damage and tree dynamics relating
directly to Ghana, and even Africa, would be very short, yet studies from other
countries are frequently of dubious relevance
· it is an open question how
far trends of logging damage, recovery and regeneration in one locality can be
extrapolated to others
· ground-based logging systems (as widely use in the
tropics) are used in Ghana for selective logging on a 40 year cycle
· within
Ghana there was no good evidence that plant biodiversity would suffer as a
consequence of logging, providing that careful logging measures are adopted
·
In Ghana, a history of `bad' logging is strongly correlated with a history of
`bad' record-keeping, thus making a historical review of logging impacts/damage
unproductive.
· As data becomes available from permanent sample plots and
growth and yield studies, the modeling of tropical forest dynamics is starting
to become feasible.
Heinrich, R. 1995. Environmental sound harvesting to
sustain tropical forests. IUFRO XX World Congress, Tampere, Finland, August
6-12, Congress Report, Volume II. p.436-446.
· Forest degradation and
forest destruction are often caused by careless unplanned and uncontrolled
harvesting of forest products in excess of their regenerative capacity.
·
This is particularly the case of timber harvesting in the rain forests in the
tropics.
· Increments of timber in plantations may be as high as 30 m3/ha/year compared to 2-8 m3/ha/year form a managed natural forest.
·
Training of forest workers is very important from both forest sustainability and
industrial accident points of view; poorly trained forest workers have more
serious accidents than well-trained workers do.
· Poor felling and
cross-cutting, as well as poor knowledge of log grading rules, also result in
volume and value loss; experience with training programs to improve
cross-cutting skills suggest that wood recovery can be improved by 20% or more,
and that the value of logs increased by 10-50%.
Hendrison, J. 1989. Damage-controlled logging in managed tropical rain forests in Suriname. Wageningen Agricultural University, Netherlands. 204pp.
· A polycyclic silvicultural system on a 20-30 year
felling cycle is most appropriate for rain forests in Suriname, than a
monocyclic silvicultural system with a rotation age of 60-80 years.
· Soil
recovery is a slow process and skid trails used 8 years previously were still
found to be maximally compacted.
· Controlled logging was found to be more
efficient than conventional logging.
· Felling productivity was more or less
the same, even with more careful and directional felling, however, skidding
production under the controlled system was twice that of conventional
logging.
· Cornerstone is planning and 100% enumeration of harvestable
commercial trees and marking all major terrain features on a large-scale map
(e.g., 1:10000 or 1:5000).
· Field staff need to be trained in all parts of
the job to allow job rotation - this give flexibility and makes the work more
interesting for the workers.
· Felling intensity is restricted in Suriname to
not exceed 30 m3/ha, in order to maintain the
ecological, conservation and protective functions of the forest.
· When tree
location maps are not available the tractor operator has to find the logs by
making trails through the forest.
· A large canopy opening may take a longer
period to recover because succession starts at the pioneer phase, while a small
gap may be closed rapidly by the crowns of trees surveying or recovering from
the felling impact.
· Timber harvesting should not be an activity on its own
but be integrated with silviculture in one forest management system.
·
Shifting cultivation along forest roads has grown almost simultaneously with the
road building program.
· Logging has become a capital-intensive operation,
the cost of which has to be recovered by raising output.
· When felled trees
are linked by lianas, a felled tree can easily damage neighbouring trees and may
even uproot them. Large open spaces may appear in the forest vegetation as a
result of the chain effect of falling trees (Fox 1968, Putz 1984).
· A
felling intensity of 5-8 trees/ha is considered to be sustainable for most types
of tropical forests (Boerboom and Wiersum 1983).
· The amount of damage done
in this operation will depend on the proposed logging intensity, and the planned
organization of the harvesting work.
· Poor work methods and techniques
during felling and terrain transport lead to splitting and breaking of felled
trees.
· Wood damage, involving serious loss of quality, can occur during
positioning and collecting (bunching) of logs with the blade of a skidder.
·
In addition, logs may deteriorate during storage in the forest and at roadside
or river landing.
· In some western countries, control of stand damage is a
management objective in harvesting systems.
· In selection felling every
effort is made to keep the remaining stand in a healthy state, by carrying out
each periodic harvest with the greatest care.
· Damage-controlled logging
aims to use the technical and ecological potential of the forest without
endangering its existence.
· direction felling is used to improve efficiency
and to restrict damage to the remaining trees
· In past operations, creaming
of the best commercial trees without replacement has led to selective forest
depletion.
· In one system used (BSH) an incentive is given to exceed a
certain production level - this in turn results in more damage to residual trees
since efficiency and not stand protection is the goal (BSH is a type of
semi-controlled logging, because no measures are taken to prevent or restrict
logging damage).
· In the period 1957-70 the logging intensity was 8-10 m3/ha.
· In the pre-logging survey an experienced
crew can cover two units (each unit is 10 ha) within a day (100% tally of all
commercial species of harvestable size (>35 cm dbh)).
· On average an
efficient trail system should be limited to cover 5-8% of the area.
· Forests
in the study had been logged previously at an VAC intensity of at least 6 m3/ha.
· Controlled felling did not influence the
number of damage trees within a gap (about 72% of the trees in a gap area were
undamaged by felling (controlled and conventional)).
· However, the area of
felling gaps was higher in the uncontrolled compartments by about 40% (had more
and larger felling gaps).
· Skid trail area was 50% less in the controlled
logging areas ( 5.4-7.3) vs. uncontrolled (conventional) (14.5 and 16.0%).
·
Wood damage was substantially higher in the conventional logging area at
24.3-28.3 % vs. 6.1-8.5% in the controlled logging area.
· More trees with
natural defects were felled in the conventional operations than in controlled
harvesting.
· Skidding should be confined to permanent rail network, built
trail on good, well drained ground, harvesting carried out during seasons when
soil damage will not occur.
· Terrain transport has become the bottleneck in
timber harvesting and often a large number of felled trees remain in the forest
for months because of limited skidding capacity.
· CELOS silvicultural
systems aim for a logging cycle of 25 years and a yield of 30 m3/ha.
· This can be achieved within the limits of
controllable logging damage, because controlled logging reduces the effect of
logging intensity.
· 20-30 m3/ha of veneer
and saw logs appears to be the most likely yield possible, when corrected for
defects, conversion losses, processability and marketability.
· The maximum
slope for economic skidding and crawling should not exceed 25% and the bearing
capacity of the soil should preferably not exceed strength class 3.
· With
controlled logging the logging damage was reduced by 40% at a logging intensity
of 20 m3/ha, and skidding area was restricted to
5-7% compared to 14% in conventional logging.
· Controlled harvesting is less
costly than conventional logging.
· Also, the study indicated that at an
operational scale, damage-controlled logging is not necessarily more expensive
than commercial logging focusing on efficiency only.
· The extra cost of
planning is returned by improved operational efficiency.
· Also, logging
intensity on the next cycle can more or less be maintained at the same
level.
Hering, K.G. 1993. Naturnahe Waldwirtschaft im atlantischen Küstenregenwald Brasiliens. Forstarchiev 64. 284-290.
· This study was carried out in southern Brazil.
·
Currently the study site is managed for commercial timber, palm hearts and
honey.
· The purpose of this study was to enhance the production of these
timber and non-timber forest products while ensuring positive returns from the
forestland.
· Harvesting operations reduced the stand density from 851 to
645 trees/ha (basal area reduced from 48.5 to 29.2 m2/ha), which is equal to a harvesting intensity of
24% of the stems or 40% of the basal area (including trees damaged during
harvesting).
· Harvesting intensities of up to 25% of the basal area ensure
sufficient regeneration of primary forest tree species.
· With an annual
growth increment of 1.8%, a cutting cycle of 12 years at a harvesting intensity
of 25% appears to be sustainable. The annual harvesting rate would equal 2.56
m3/ha.
· A comparison of management scenarios
for a forest area of 2,208 ha indicated that sustainable management practices
result in a present value of US$ 2.2 million compared to US$ 5.6 million with
timber exploitation.
Hernández-Diaz, J.C. and M. Delgado-Pacheco. 1996. Damage evaluation of the remaining standing trees in a timber yarding operation (case study). In: Proceedings of Forest Operations for Sustainable Forestry, XX IUFRO, World Congress, August 6-12, 1995. IUFRO S3.05-00 and CIFOR Publication. p.33-37.
· study of a small cable yarding operation in selective
cutting in Mexico
· initial stand volume 163.1 m3/ha (113 adult trees/ha)
· marked volume 65.3
m3/ha (45.3 trees/ha marked)
· extracted
volume 41.4 m3/ha (45.3 trees/ha felled) (63% of
marked volume utilized)
· average piece size 0.78 m3
· of the residual commercial volume 4.6 m3/ha had severe or medium damage (about 4.7%)
Holdsworth, A.R. and Uhl, C. 1997. Fire in Amazonian selectively logged rain forest and the potential for fire reduction. Ecological Applications 7(2): 713-725.
· The study area was located near Paragominas in the
eastern Amazon, Brazil.
· Low impact logging reduced the mean size of canopy
gaps by 53% relative to conventional logging.
· Fire reduces the potential
value of the forest, but by reducing the size of logging gaps low impact logging
techniques can reduce the risk of fire.
· An average extraction intensity
for the Paragominas region is 30-40 m3/ha with a
cutting cycle of 30-50 years.
· Using low impact logging techniques, 50
US$/ha are required to carefully plan and execute logging operations.
·
According to Barreto et al.1998 the additional costs
of low impact logging would be completely recovered by the additional
benefits.
van der Hout, P. 1999. Reduced impact logging in the tropical rain forest of Guyana. Ph.D. thesis. University of Utrecht, Netherlands. 331pp.
· This study was carried out in the Upper Demarara
district of Guyana.
· Reduced impact logging was studied with harvesting
intensities of 4, 8 and 16 trees/ha.
· With conventional logging an average
of 8.7 trees/ha was harvested (basal area 2.2 m2, or 27.8 m3/ha).
The variability was high (0 to 25 trees/ha harvested).
· Mean loss of canopy
cover as percentage of total area:
|
Type of logging |
Loss of canopy cover (%) |
Loss of canopy cover per tree extracted (m2) |
Mean gap size (m2) |
Number of gaps per hectare |
|
Conventional | ||||
|
8/ha |
15.8 |
198 |
264 |
6.0 |
|
16/ha |
24.5 |
153 |
439 |
5.7 |
|
Reduced impact | ||||
|
4/ha |
8.5 |
208 |
185 |
4.6 |
|
8/ha |
15.7 |
192 |
209 |
7.7 |
|
16/ha |
30.1 |
184 |
333 |
9.0 |
|
Percentage of total area (%) | |||
|
Trails |
Other movements |
Total | |
|
Conventional | |||
|
8/ha |
8.2 |
4.7 |
12.9 |
|
16/ha |
9.9 |
10.8 |
20.7 |
|
Reduced impact | |||
|
4/ha |
4.9 |
0.1 |
5.1 |
|
8/ha |
7.6 |
0.4 |
8.0 |
|
16/ha |
8.3 |
0.5 |
8.1 |
· Ground disturbance in felling gaps occurred significantly more often in conventional logging than in reduce impact logging; an average 6.7% of the total area as opposed to an average 1.1%.
· Conventional logging severely damaged a basal area of
1.5 m2/ha (an estimated 5.1% of the original
stand) with no significant relation to logging intensity. Reduced impact logging
seriously damaged a basal area of 0.5 m2/ha
(2.1% of the initial stand) after a light harvest, and a basal area of 1.8 m2/ha (7.6% of the initial stand) was damaged with a
logging intensity of 16 trees/ha.
· In the reduced impact operation a higher
proportion of tree damage was due to felling than in the conventional operation.
An increase in logging intensity raised the proportion of damage due to felling
as opposed to skidding.
· Reduced impact logging reduced the number of trees
killed by skidding by 24 trees/ha.
· During the entire operation trees
between 20 and 40cm dbh were relatively more frequently damaged. This may be due
to their relatively large crowns when compared to smaller size classes.
·
Compared to conventional logging reduced impact logging damaged trees between 20
and 40cm dbh less frequently, large trees more frequently, and a similar
proportion of the trees between 10 and 20cm dbh.
· RIL is effective in
reducing skidding damage to small and medium sized trees. However, the level of
felling damage increases when RIL is implemented.
· With conventional
logging, 85% of the residual stand are likely to survive at a harvesting
intensity of 8 trees/ha, at a harvesting intensity the rate of survival will be
reduced to 77%.
· With RIL, 89% of the trees will probably survive at a
harvesting intensity of 8 trees/ha (78% at 16 trees/ha).
· Survival rates
are highest among large trees (92 to 96%) and lowest among small trees (71 to
87%).
· Directional felling did not result in a smaller number of affected
commercial trees, but it may have had an affect on the severity of the damage. A
positive impact of directional felling was noted in the field but could not be
verified statistically.
· With a cutting cycle of 25 years and neglecting
mortality, harvesting intensity of 8 trees/ha may be possible. However, for the
following cutting cycle all trees will have to be recruited from the 20-40cm dbh
size class, which will take much longer than 25 years. With the same
assumptions, stand table projection with a harvesting intensity of 8 trees/ha
indicate 27 trees/ha in the 40cm and above size class after 25 years, which
suggests that this exploitation level may be sustainable.
· In this study RIL
reduced the damage to the residual stand by 6% at an extraction level of 8
trees/ha, and by 3% at an extraction level of 16 trees/ha.
· RIL resulted in
a reduction of the skid trail coverage from 13% to 8% of the total area at a
logging intensity of 8 trees/ha and from 21% to 85% at an intensity of 16
trees/ha.
· Liana cutting did not seem to have any effect. However, cutting
lianas 6 months prior to harvesting is probably too short a period (only 50% of
the trees had died 6 months after cutting).
· Fewer composite gaps occurred
with reduced impact logging.
· Due to implementation of RIL the proportion of
residual trees damaged by skidding was reduced from 12% to 8% at a logging
intensity of 8 trees/ha and from 16% to 9% at a logging intensity of 16
trees/ha.
· Due to implementing RIL techniques the level of felling damage
was reduced from 15% to 12% at a logging intensity of 8 trees/ha whereas an
increase from 22% to 24% was found at a logging intensity of 16 trees/ha.
·
It was found that the number of trees irreversibly damaged by felling did not
differ at a harvesting intensity of 8 trees/ha - remaining at 8% - but increased
strongly at an intensity of 16 trees/ha - an increase from 12% to 18% by
applying RIL techniques.
· Felling and skidding damage taken together, this
equals a reduction of irreversible residual damage from 15% to 11% (at 8
trees/ha) and from 22% to 21% (at 16 trees/ha) respectively.
· In
conventional logging, felling reached a productivity of 10 m3/h per crew while in reduced impact logging
productivity only reached a level of 5.8 m3/h
(reduction in felling performance 37% while the operative machine time was
increased by 66%).
· For skidding the volume delivered at the landing per
operative machine hour increased from 11.8 m3/h
to 14.4 m3/h when RIL guidelines were
implemented.
· Costs of pre-harvest planning for conventional and reduced
impact logging in US$/ha (Costs are incurred one year prior to harvesting):
|
Activity |
Costs (US$/ha) | |
|
Conventional Logging |
Reduced Impact Logging | |
|
Block lay-out |
2.08 |
2.80 |
|
Inventory |
2.45 |
7.66 |
|
Liana cutting |
0.00 |
3.99 |
|
Data processing |
0.23 |
0.46 |
|
Map making |
0.10 |
0.43 |
|
Road planning |
0.20 |
0.20 |
|
Total |
5.06 |
15.52 |
· Costs of harvest preparation for conventional and reduced impact logging in US$/ha (The road density of primary roads is 2m/ha and of secondary roads is 10m/ha. The area occupied by landings amounts to 50 m2/ha. Costs are incurred six months prior to harvesting):
|
Activity |
Costs (US$/ha) | |
|
Conventional Logging |
Reduced Impact Logging | |
|
Road construction |
||
|
Primary road |
6.42 |
6.42 |
|
Secondary road |
4.61 |
4.61 |
|
Landing construction |
3.84 |
3.84 |
|
Skid trial demarcation |
- |
2.37 |
|
Total |
14.87 |
17.24 |
· Reduced impact logging thus increases the up-front
costs by US$ 12.83/ha (NPV = $14.69/ha) which have to be recovered by more
efficient harvesting operations.
· Cost of felling, skidding and landing
operations for conventional and reduced impact logging in US$/m3 and output expressed as m3 per effective crew hour (felling and landing
operations) or effective machine hour (skidding) [flat to rolling terrain,
logging intensity of 10 trees/ha, standard load of 9.7 m3 per trip, average straight-line distance 383
m]:
|
Activity |
Conventional Logging |
Reduced Impact Logging | ||
|
Costs ($/m3) |
Output (m3/h) |
Costs ($/m3) |
Output (m3/h) | |
|
Felling and bucking |
0.60 |
10.6 |
1.16 |
6.7 |
|
Skidding |
4.30 |
14.4 |
4.10 |
15.9 |
|
Landing operations |
0.34 |
19.3 |
0.32 |
20.9 |
|
Total |
5.24 |
5.58 |
||
· Costs per m3 and equivalent volume output per day of support, logistics and supervision (Estimates are based on a daily output per logging team of 84 m3 for conventional logging and 97 m3 for reduced impact logging, at logging intensities of 28.5 and 31.0 m3/ha respectively):
|
Activity |
Conventional Logging |
Reduced Impact Logging | ||
|
Costs ($/m3) |
Output (m3/h) |
Costs ($/m3) |
Output (m3/h) | |
|
Road maintenance |
1.91 |
167 |
1.64 |
195 |
|
Logistics |
2.88 |
84 |
2.48 |
97 |
|
Supervisor |
0.26 |
84 |
0.22 |
97 |
|
Cooks |
0.23 |
84 |
0.20 |
97 |
|
Base camp |
1.66 |
- |
1.66 |
- |
|
Administration costs |
0.33 |
- |
0.33 |
- |
|
Royalty |
2.68 |
- |
2.68 |
- |
|
Area fee |
0.21 |
- |
0.19 |
- |
|
Total |
10.17 |
- |
9.40 |
- |
· In the conventional logging operation the average
volume recovered per tree amounted to 2.9 m3
whereas a volume of 3.1 m3 was recovered on
average in the RIL operation.
· The extra investment during the felling
phase in RIL was mainly benefiting the performance of the skidding phase and
only marginally the higher wood recovery.
· For reduced impact logging the
change in the aggregate logging cost (per m3) is
small (increase of 5%) when the logging intensity is reduced from 16 to 8
trees/ha (from 50 to 25 m3/ha). The cost rises
more strongly when the harvesting intensity is further reduced to 4 trees/ha and
even more when subsequently being reduced to 2 trees/ha [the absolute financial
values and differences should not be taken too seriously. The results are all
based on projections from the observed situation with a logging intensity of 10
trees/ha]:
|
Logging intensity (trees/ha) | ||||
|
2 |
4 |
8 |
16 | |
|
Pre-harvest planning |
2.42 |
1.21 |
0.61 |
0.30 |
|
Harvest preparation |
2.69 |
1.34 |
0.68 |
0.34 |
|
Felling & bucking |
1.18 |
1.17 |
1.16 |
1.14 |
|
Skidding |
4.25 |
4.17 |
4.08 |
4.01 |
|
Landing operations |
0.32 |
0.32 |
0.32 |
0.32 |
|
Trucking, loading and unloading |
13.54 |
12.69 |
12.26 |
12.04 |
|
Road maintenance |
2.12 |
1.82 |
1.66 |
1.57 |
|
Support, logistics & supervision |
3.68 |
3.20 |
2.94 |
2.79 |
|
Other overhead costs |
1.99 |
1.99 |
1.99 |
1.99 |
|
Royalty and fee |
3.63 |
3.15 |
2.92 |
2.79 |
|
Total cost |
35.83 |
31.08 |
28.62 |
27.30 |
· In the long term several benefits are associated with
reduced impact logging. Attempts to place a financial value on these are neither
realistic nor even desirable for that very reason.
· The financial appraisal
showed that reduced impact logging is cost competitive with conventional
logging. The direct costs per cubic metre may have been 12% higher, which was
mainly related to higher planning and felling costs. There are strong
indications that the cost of felling will be reduced in the future when the
operators have gained more experience in using the felling method. In the
present study, the additional costs were offset by a higher per day and per
area, which reduced direct cost components such as road construction as well as
indirect costs such as logistics, supervision and support.
van der Hout, P. 2000. Testing the applicability of reduced impact logging in greenheart forest in Guyana. International Forestry Review 2(1): 24-32.
· The study was conducted at Pibiri in Central
Guyana.
· For conventional logging two harvesting intensities (8 stems/ha and
16 stems/ha) were evaluated. Due to the clumped distribution of commercial trees
the absolute logging intensity varied over the area, ranging from 0-78 m3/ha. 96% of the extracted trees were Chlorocardium rodiei.
· For reduced impact logging,
harvesting intensities of 4, 8 and 16 stems/ha were analysed. A harvesting
intensity of 8 stems/ha corresponds to a volume of 25 m3/ha. The share of Chlorocardium rodiei was reduced to 53% of the cut
trees.
· It must be noted that in this case conventional logging operation
featured felling in groups while trees were scattered in the RIL operation.
· RIL resulted in a greater loss of canopy if the logging intensity was
increased above 8 trees/ha.
· In the conventionally logged blocks, the
average canopy opening per felled tree decreased by 23% when the harvesting
intensity was increased from 8 to 16 trees/ha.
· Implementation of RIL
techniques reduced the area traversed by the skidder by about 2/3 depending on
the logging intensity, while skidder movements in felling gaps were reduced by
about 3/4 (also depending on the logging intensity).
· By adopting RIL,
felling damage was reduced by 16% at a logging intensity of 8 trees/ha, whereas
it was augmented by 9% at a logging intensity of 16 trees/ha.
· No
difference was found in the size of single tree fall gaps. Liana cutting and
directional felling as carried out in this study did not reduce the amount of
canopy loss.
· Skidding appeared to have a lower impact in the RIL operation
than in the conventional logging operation.
· The gross volume recovery rate
increased from an average of 2.9 to 3.1 m3 over
bark by implementing RIL techniques.
· RIL reduced the felling performance by
37% while the operative machine time was increased by 66%.
· The
implementation of RIL increases the skidding output from 14.4 to 15.9m3/h.
· Cost of logging of conventional and reduced
impact logging:
|
Operation |
Conventional (US$/m3) |
Reduced Impact (US$/m3) |
|
Pre harvest planning |
0.18 |
0.50 |
|
Harvest preparation |
0.52 |
0.56 |
|
Felling and cross-cutting |
0.60 |
1.16 |
|
Skidding |
4.30 |
4.10 |
|
Landing operations |
0.34 |
0.32 |
|
Trucking, loading and unloading |
12.18 |
12.18 |
|
Road maintenance |
1.91 |
1.64 |
|
Support, logistics and supervision |
3.37 |
2.90 |
|
Other overhead costs |
1.99 |
1.99 |
|
Royalty and area fee |
2.89 |
2.88 |
|
Total |
28.29 |
28.23 |
· RIL systems are neither necessarily more expensive,
nor cheaper than harvesting with conventional techniques.
· RIL resulted in a
very modest reduction in residual stand damage and canopy loss. Only the
reduction of the skidding trail coverage is in agreement with the results of
other studies.
· Residual damage in conventional operations in Guyana was
lower than in most RIL operations elsewhere. Therefore the spectacular
reductions in other studies should be seen against a higher benchmark.
Hutchinson, I.D. 1987a. Improvement thinning in natural
tropical forests: aspects and institutionalization. In: Mergen, F. and J.R.
Vincent (eds.). Natural Management of Tropical Moist Forests - Silvicultural and
Management Prospects of Sustained Utilization. Yale University, School of
Forestry and Environmental Studies, New Haven, Connecticut. p.113-133.
·
From 1974-1980 selective logging in Sarawak MDF extracted an average of 5-15
trees/ha (10-50 m3/ha).
· With improvement
thinning could have a polycyclic system with 60-year rotation and 30 year
cutting cycle.
· In MDF forest in Malaysia, mean annual dbh increment of
trees >10 cm dbh in control (all trees) was 0.22-0.34 cm/year, with overstory
removal 0.37-0.44 cm/year, and with liberation thinning 0.45-0.56 cm/year (in
this case if only reserved trees measured 0.77-0.99 cm/year).
Hutchison, I.D. 1987b. The management of humid tropical forest to produce wood. In: Proceedings of Management of the Forests of Tropical America: Prospects and Technologies, San Jan, Puerto Rico, September 22-27, 1986. USDA, Forest Service, Southern Forest Experiment Station. 121-155.
· Report gives the same logging intensity as in the
previous article.
· The study showed that the incidence of injury per wood
quality group did not differ significantly; i.e., loggers disregard the
protection of standing stems of desirable species.
· Only 15 desirable
stems/ha were recorded as being both of potentially commercial log grade and
free from injury.
· Incidence of injury can be reduced by regular inspections
and direction of operations by trained and experienced staff, and by
post-logging inspection and enumeration.
· Selective logging eliminated 20%
of the total number of stems that existed in the virgin forest, snapped the
trunks of 5% and injured more than 66% of all stems >= 10 cm dbh.
·
Improvement thinning after logging is necessary to improve the quality of the
stand, otherwise it just degrades with each cutting cycle; e.g., 60% of the
basal area per hectare of surviving trees with fully illuminated crowns
comprised stems with visible decay, while 20% were recorded as being totally
decayed.
· Without an improvement cut a significant component of the growth
will be on unmerchantable trees.
· 40% of medium-sized trees were damaged by
selective logging, thus jeopardizing the yield in the second cut.
· The
incidence of total destruction of stems by selective logging falls most heavily
on the small dbh classes.
· A minimum felling limit is needed to limit the
intensity of the logging operations; this however needs to be complemented by
improvement thinning.
Inglis, C.J., G. Sutton and G.J. Lawson. 1997. Research and monitoring for sustainable forest management in North-west Guyana. In: Proceedings of the FAO/IUFRO Satellite Meeting held in conjunction with the IUFRO XX World Congress, Tampere, Finland, 4-5 August, 1995, Research on Environmentally Sound Forest Practices to Sustain Tropical Forests. Food and Agriculture Organization of the United Nations. p.27-36.
· BCL sets the minimum dbh for felling at 50-60 cm for
the plywood mill.
· There are on average 7 trees/ha which fulfil the species,
size and quality requirements for the mill and in fact only 5 trees/ha are being
felled (average tree size is 3 m3 = 15 m3/ha).
· This is lower than in north-eastern
Brazil where 6 trees/ha (38 m3/ha) are harvested
(Verissimo et al. 1992).
· For every 6 trees logged a further 21 were either
pushed or pulled over or were snapped (1 bent, 17 pushed over, 4 crown snapped,
4 severe crown damage).
· Of the original 227 trees/ha (dbh >20 cm, 183
were not felled and had no logging damage.
· A need for evaluation of the
effectiveness of pre-logging climber cutting.
· The CELOS system has partly
guided the logging operations at BCL.
ISTF. 1995. IMAZON logging improvement Note. International Society of Tropical Foresters News 16(1): 1,10.
· RIL with vines cut 18 months prior to logging.
·
Directional felling made 85% of the felled trees easier to skid; about 40% were
naturally in a good position, relative to the skid trail.
· Improved skidding
operations resulted in less forest damage, less timber extraction time and lower
extraction cost, than in the conventionally logged area.
· RIL looked much
better, skid trails had good regeneration and canopy cover, the openings looked
very similar to natural tree fall gaps.
· Vine cutting, directional felling
and removal of buttresses clearly helped reduce damage and increased skidding
efficiency.
· RIL stand suffered one-third less damage than the
conventionally logged stand.
· The potential impact of an industry conversion
to RIL is enormous.
· Adoption of RIL throughout the tropics would result in
more efficient use of production forests that in turn would reduce pressure on
primary forests.
· IMAZON results suggest costs may be reduced by
one-third.
ITTC, 1990. The promotion of sustainable forest management: a case study in Sarawak, Malaysia. Report by the ITTC Mission, Earl of Cranbrook (ed.) ITTC, Denpasar, Indonesia. 208pp.
· Prospective timber yield - Cutover Hill Mixed Forest (harvesting to the minimum dbh and assuming reduced impact logging):
|
Diameter classes |
60+ cm |
45+ cm |
30+ cm | |||
|
Wood quality group1 |
1 |
1-3 |
1 |
1-3 |
1 |
1-3 |
|
Aver. residual crop - number/ha - m3/ha |
0.9 3.4 |
1.0 3.8 |
6.7 15.4 |
8.3 18.8 |
13.1 22.0 |
17.0 27.8 |
|
Predicted harvestable volume by cutting cycles, m3/ha | ||||||
|
25 years - untreated - treated |
8.6 18.5 |
10.1 22.6 |
27.4 32.6 |
34.8 41.9 |
41.3 54.2 |
45.6 69.9 |
|
30 years - untreated - treated |
14.3 23.4 |
17.6 29.2 |
29.3 43.0 |
37.4 55.4 |
45.2 60.7 |
49.1 78.3 |
|
35 years - untreated - treated |
20.0 28.3 |
25.1 35.8 |
32.0 53.4 |
42.5 68.9 |
Growth data incomplete | |
|
40 years - untreated - treated |
25.7 33.2 |
32.6 42.4 |
37.7 63.8 |
47.6 82.4 | ||
|
45 years - untreated - treated |
31.4 38.1 |
40.1 49.0 |
43.4 74.2 |
55.1 95.9 | ||
|
50 years - untreated - treated |
37.0 43.0 |
47.6 55.4 |
49.0 84.8 |
62.6 109.2 | ||
1Wood quality group 1 contains 179 timber tree species (5% of tree flora), while group 1-3 contains 785 tree species (23% of tree flora)
· It is seen that if the harvest were limited to trees
of 60 cm dbh or more and to the choice no. 1 group, long cutting cycles (45-50
years) would be necessary to attain the present harvest of 38 m3/ha.
· More realistic would appear a minimum dbh
of 45 cm with species groups 1-3, permitting a 35 year cutting cycle.
·
Indicated cutting cycles for hill forests (to produce a minimum 38 m3/ha):
|
Minimum dbh, cm |
Species group |
Indicated cycle, years | |
|
Untreated |
Liberated | ||
|
60 45 30 60 45 30 |
1 1 1 1-3 1-3 1-3 |
50 40 25 45 35 20 |
45 30 15 40 25 10 |
· The above yields can never be attained by continuing
present practice, which is damaging to the environment and the residual
stand.
· The practices of the labour force in the forest directly cause much
of the damage; practically no formal training for fellers or tractor and skidder
drivers (experience is passed from one to the other). It is hardly surprising,
therefore, that little attention is paid by the fellers to limiting damage to
the residual stems or by skidders to this or other effects on the
environment.
· Tractor and skidder operators are paid piece rates by most
companies, and fellers apparently by all companies. The emphasis is on output
and not on the minimization of damage.
· Safety standards are usually of a
low standard.
· These weaknesses are exacerbated by inadequate staffing of
the Forest Department and the consequent inability to exercise the degree of
supervision required.
ITTO, 1992a. ITTO guidelines for the sustainable management of natural tropical forests. International Timber Trade Organization, Yokohama, Japan, Policy Development Series 1. 18pp.
· "To encourage the development of national policies
aimed at sustainable utilization and conservation of tropical forests and their
genetic resources, and a maintaining the ecological balance in the regions
concerned."
· Principle 12: Proper planning, at national, forest management
unit and operational levels reduces economic and environmental costs and is
therefore an essential component of long-term sustainable forest management
·
Possible action 13: The Annual Allowable Cut (AAC) should be set conservatively
in the case of absence of reliable data on the regeneration and growth dynamics
of tree species, especially with regard to diameter increment and response to
the effect of logging on trees and soils. This applies both to tree species
which, under current market conditions, are desirable or which have the
potential to become commercially attractive in the future, recognizing that
domestic and world markets for forest produce are under very dynamic
development. In practice, this will often mean conservative setting of rotation
length, felling cycle and girth limits. As and when permanent sample plots begin
to yield more reliable information about dynamics of desirable species, a
reassessment of AAC should be considered.
Possible action 15: Management inventory and mapping should be carried out
Possible action 16: Preparation of working plans
Principle 21: Harvesting operations should fit into the silvicultural concept, and may, if they are well planned and executed, help to provide conditions for increased increment and for successful regeneration. Efficiency and sustainability of forest management depend to a large extent on the quality of harvesting operations. Inadequately executed harvesting operations can have far-reaching negative impacts on the environment, such as erosion, pollution, habitat disruption and reduction of biological diversity, and may jeopardize the implementation of the silvicultural concept
Principle 22: Pre-harvesting prescriptions are important to minimize logging damage to the residual stand, to reduce health risks for logging personnel and to attune harvesting with the silvicultural concept
Possible action 19: To draw up detailed prescriptions, including measures such as climber cutting, marking of trees to be felled and/or residuals to be retained and indications of extraction direction and felling direction
Principle 23: Planning, location, design and construction of roads, bridges, causeways and fords should be done so as to minimize environmental damage
Principle 24: Extraction frequently involves the use of heavy machinery and, therefore, precautions must be taken to avoid damage
Principle 25: Post-harvest operations are necessary to assess logging damage, the state of forest regeneration, the need for releasing and other silvicultural operations to assure the future timber crop
Appendix 3 (Roads and Harvesting) list considerations important on grounds of efficiency and to minimize environmental damage
ITTO, 1992b. Criteria for the measurement of sustainable tropical forest management. International Timber Trade Organization, Yokohama, Japan, Policy Development Series No. 3. 5pp.
· Part of the process to achieve ITTO's Target 2000 to
ensure that all trade in tropical timber is sourced from sustainably managed
forests by the year 2000.
· Sustainable forest management is the process of
managing permanent forest land to achieve one or more clearly specified
objectives of management with regard to the production of a continuous flow of
desired forest products and services without undue reduction of its inherent
values and future productivity and without undue undesirable effects on the
physical and social environment.
ITTO, 1993a. ITTO guidelines for the establishment and sustainable management of planted tropical forests. International Tropical Timber Organization, Policy Development Series No. 4. 38pp.
· Plantations will have a major role in fulfilling
societal fibre requirements and to reduce pressure on natural forests.
· On
the other hand, it would be wrong to assume that planted forests could
substitute for natural forests and replace them as source of raw materials and
environmental and social benefits. Such assumptions could lead to natural
tropical forests being cleared to provide sites for industrial forest
plantations which promise to produce much higher volumes of timber per unit
area. However, major social conflicts may also arise from industrial plantations
displacing existing landholders and disrupting prevailing patterns of land-use.
Possible detrimental environmental and ecological effects of large-scale
introductions of exotic tree species are also emerging as major concerns and
policy issues in some tropical countries and amongst the international
community.
· Actions recommended have a lot to do with BMPs and management
and operational planning at all phases.
· Links logging operations directly
in with silviculture.
ITTO, 1993b. ITTO guidelines on the conservation of biological diversity in tropical production forests. International Tropical Timber Organization, Policy Development Series No. 5. 18pp.
· Recommended action 11 - In forest areas of recognized
importance for biodiversity conservation incorporate consideration of the
effects of rotation length, felling cycles, girth limits and size of the annual
area cut-over in deciding the allocation of the AAC.
· Recommended action 12
- when determining yield allocations and rotation lengths for particular
management units, plan logging operations so that a mosaic of recently logged
and old growth forests are maintained over time.
· Recommended action 16 -
reduce individual gap size as far as possible, unless specifically required for
the regeneration of key species. Avoid creating very large gaps that equate to
areas of local clearfelling.
· Recommended action 17 - minimize machinery and
felling damage to the residual stand, undergrowth and soil.
ITTO. 1996. Reduced impact, increased cost? ITTO, Tropical Forest Update 6(3): 10-12.
· A certain level of RIL can be achieved simply through
careful planning, scheduling and control of logging operations.
· Cost of
implement RIL in Malaysia 2.05 USD/m3 or 82
USD/ha (does not included additional cost of pre-logging inventory or training
of felling crews and supervisors).
· Benefits assumed to be reduced skid
trails from 250 m/ha to 200 m/ha (conservation reduction) (saving = 0.50
USD/m3 @ 393.70 USD/km of skid trail).
· 20%
increase in skidding productivity results in a decrease from 393.70 USD/ha (9.84
USD/m3) to 314.96 USD/ha (7.87 USD/m3) = 1.97 USD/m3.
· RIL cost = 2.05 USD/m3 with a logging cost saving of 2.47 USD/m3 or 0.42 USD/m3.
· In addition to saving in logging costs there
would be a substantial long term increase in timber yield.
· A reduction in
logging damage from 20 to 15 trees/ha would result in a saving of 7.5 m3/ha (5 trees @ an average 1.5 m3/tree) of residual wood volume. Additional growth on
these trees of 10 m3/ha over a 25 year periods
could be expected, of which about 70% would be commercially recoverable timber.
The overall additional wood fibre would thus be 14.5 m3/ha after 25 years, which could work out to 1184
USD/ha more revenue for the logger on the next harvest.
· One of the most
significant benefits of RIL is the increase in value of the next harvest, but
this is hardly likely to impress the holders of short-term concession rights
who, above all, are the ones who must be convinced that RIL is in their best
interests.
· Also need to implement training programs, which are mainly
lacking in developing countries.
· Also have to deal with concession system,
the performance of regulatory bodies, the expectations of society and the
willingness of outside players to pay for various products and services from the
forest.
Ivo, W.M., S. Ferreira, Y. Biot and S. Ross. 1996. Nutrients in soil solution following selective logging of a humid tropical `terre firme' forest north of Manaus, Brazil. Environmental Geochemistry and Health 18(2): 69-75.
· Selective logging removed 35 m3/ha of wood.
Jabil, M. 1983. Problems and prospects in tropical rainforest management for sustained yield. Malaysia Forester 46(4): 398-408.
· With the apparent failure of forest management in most
tropical countries, there has been a growing tendency to question the validity
and practicality of the concept of sustained yield in tropical rainforest
management.
· The resultant controversy has been heightened by the successful
introduction of fast-growing species in recent years in some tropical
countries.
· This has led to the naive conclusion that the solution of the
problems in tropical rainforest management lies in abandoning the natural
forest.
· While the need for plantations cannot be denied, particularly in
meeting long-term wood supply objectives, sustained yield management of the
natural forest is imperative in most tropical countries.
· The successful
practice of tropical rainforest management for sustained yield requires not only
technical expertise and appropriate technologies but also careful planning and
implementation.
Johns, A.D. 1988. Effects of "selective" timber extraction on rain forest structure and composition and some consequences for frugivores and folivores. Biotropica 20(1): 31-37.
· Mechanized logging using heavy bulldozers and highlead
yarding.
· In a West Malaysian dipterocarp forest the mechanized extraction
of 3.3% (18 trees/ha) of trees (>=30 cm dbh) destroyed 50.9% (3.3% timber
trees/4.8% destroyed during road building/3.6% destroyed when building landings
and spar tree sites/39.2% destroyed during felling operation and log dragging)
of the trees and damage was spread equally among all tree taxa and all size
classes.
· Of the 49.1% remaining trees 6.0% were standing but damaged.
·
18.3 stems/ha of marketable timber (24 m2/ha)
were extracted with minimum girths of 145-192 cm (46-61 cm dbh depending on
species).
· Since only 3.3% of the stems were removed with 50.1% destroyed
the term selective logging does not apply.
Johns, A.D. 1991. Responses of Amazonian rain forest birds to habitat modification. Journal of Tropical Ecology 7(4): 417-437.
· Study of terre firme rain forest in Amazonas
State.
· Logged during 1975-85 with a logging intensity of 3-5 trees/ha (main
tree cut Cedrelinga cateniformis).
· Damage was
considerable at the time due mainly to careless siting of skid roads.
·
However, the forest had since regenerated over 11 years to a basal area of at
least 15 m2/ha, compared to 35 m2/ha in unlogged forest.
Johns, A.D. 1992. Species conservation in managed
tropical forests. In: Whitmore, T.C. and J.A. Sayer (eds.), Tropical
Deforestation and Species Extinction. IUCN, Chapman and Hall, London.
P.15-50.
· Logging is most often controlled by entrepreneurs, to whom
short-term profits are of prime importance, rather than by foresters, whose duty
is to the long-term maintenance of the resource.
· A logging contractor, or a
contractor with a short-term lease, will be concerned only with a single cut and
will not be motivated to minimize environmental damage.
· Lack of financial
interest in the future crop is probably the main reason for the excessive damage
levels typical of short-term extraction operations.
· Commercial logging in
tropical rain forests can take a number of forms, almost all of which involve
the removal of selected trees rather than the clear-felling of whole stands. The
only exceptions are three operations (Columbia, Papua New Guinea, Sabah) where
forests are clear-felled for wood chips.
· In Amazonia, up to 140 species may
be logged in the eastern forests accessible both to local markets and to the
populated regions of southern Brazil (Uhl and Viera, 1989), whereas a few as two
or three species may be cut in the isolated western regions (Johns 1988a).
·
Harvesting intensity in tropical forests varies considerably from 1 to 72
trees/hectare depending on the forest type and country.
· Malaysian
dipterocarp forest up to 72 trees/ha felled (extremes that result in total
destruction of the forest canopy), with an average being 14 trees/ha.
· Most
Amazonian terra firme forests yield only 3-5 trees/ha.
· This equal to level
2 harvesting at about 10-15 m3/ha/cycle (Braz
and d'Oliviera 1995).
· Level 3 harvesting will be more intensive and remove
30-40 m3/ha/cycle (Braz and d'Oliviera
1995).
· Some African forests as low as 1.1 trees/ha.
· The number of
species used is increasing in many parts of the world.
· In the 80's 8.4-13.5
m3/ha for neotropical and African forests
(Freezailah 1984).
· In Asian dipterocarp forests generally more than 50
m3/ha, and in Sabah up to 110 m3/ha.
· Monocyclic systems - remove all
merchantable trees in a single operation - come back in 70 years time.
·
Polycyclic systems - lower initial felling intensity, designed to limit damage
to advance regeneration of commercial species which become a viable second crop
after only 20-30 years.
· An emergent tree of >2.5 m girth will destroy
around 0.02 ha on falling (Dawkins 1959).
· Main access roads through the
forest have ROW widths of 20-30 m wide to allow sun to reach the ground and thus
dry up the road faster.
· These roads and their landing areas occupy from
6-20% of the forest (Hamzah 1978, Malvas 1987).
· Skid roads in the cut area
average 4 m in width and can be 270 m/ha.
· Kartawinata (1978) estimates that
30-40% of the logged forest in Indonesia may be left bare of vegetation as a
result of roading and dragging activities.
· Some kind of damage to 40% of
the residual trees is common (Abdulhadi et al. 1981).
· Post harvest
windthrow can also be increased due to the uneven nature of the canopy after
logging and increased wind turbulence.
· A study in Sarawak (Marn and Jonkers
1981, Marn 1982) showed that felling trees in the direction which caused least
damage, careful siting of skidroads and the restriction of
tractors to them
reduced damage levels by half without increasing cost.
· Results from
Queensland in fact suggest that logging reverses a natural loss of diversity
that occurs as a forest matures after disturbance and pioneer species die out
(Nicholson et al. 1988). However, logged forests may not always regain all
species lost during logging and their species composition may be somewhat
different.
· It is generally recognized that damage levels attached to
current logging operations, particularly intensive logging operations, are
unnecessarily high.
· Experimental operations in Sarawak and Sabah have shown
that the levels of incidental damage, even under intensive harvesting, can be
reduced by as much as half (Marn 1982, Malvas 1987).
· There is an optimum
canopy gap size at which the regeneration of timber trees may be affected.
Larger gaps caused by felling too many adjacent trees commonly stimulate the
growth of commercially useless pioneer tree species, woody climbers and shrubs,
which can be a bane to future management operations.
· In most tropical
forests, the most effective form of forest management is undoubtedly protection
and encouragement of advanced growth in optimally sized gaps created during
logging, with planting of gaps where no advanced growth exists.
Johns, J.S., P. Barreto and C. Uhl. 1996. Logging damage during planned and unplanned logging operations in the eastern Amazon. Forest Ecology and Management 89: 59-77
· For each commercial tree felled, unplanned logging
damaged 16 more trees >= 10 cm dbh and affected a ground area that was 100
m2 greater than in planned operations.
·
Unplanned vs. planned (severe crown damage 7.4 vs. 4.5 trees/trees felled)
(trees smashed to the ground 7.2 vs. 4.9 trees/trees felled).
· More trees
experienced moderate or severe damage along unplanned skid trails than along
planned skidder skid trails. These differences are particularly pronounced in
the bole damage categories (7.9 trees >10 cm dbh smashed and 5.3 trees >10
cm dbh with moderate bole damage per 100 m of unplanned bulldozer skid trails
vs. 5.3 trees smashed and 2.2 trees with moderate bole damage per 100 m of
planned skidder skid trails).
· Unplanned felling damaged almost 2x as many
trees per hectare as planned felling (124 vs. 64).
· Damage to individual
trees was reduced in the planned logging operation by cutting vines 2 years
prior to logging and by implementing directional felling.
· Estimate the
profit margins for companies doing planned fellings will increase.
· Planned
logging costs offset by benefits from reduced machine operating hours and labour
per m3 of timber extracted and less waste.
·
More than 80 trees per hectare were spared damage with planned logging.
·
With planned logging damages can be reduced by 25-33% and the logging can be
done on a 30-40 year cycle.
· With a planned harvest, subsequent cuts should
yield more or less the same volume as the first harvest, otherwise 75-100 years
would be required to get the same logging intensity.
· Presently logging in
Brazil Amazon is done carelessly, and even though only a few trees are removed
the forest is left in a highly degraded state.
· Logging intensity in planned
logging 37 m3/ha (=4.5 trees/ha >52 cm
dbh).
· Logging intensity in unplanned logging 30 m3/ha (=5.6 trees/ha >45 cm dbh).
· The total
ground area affected by the planned skidder operation was 1503 m2/ha, planned bulldozer operation 1706 m2/ha, and unplanned bulldozer operation 2276 m2/ha.
· The biggest differences are found in
maneuvering the machine in the bole area (254 m2/ha unplanned bulldozer vs. 23 m2/ha planned bulldozer vs. 45 m2/ha planned skidder), constructing log landings (153
m2/ha unplanned vs. 61 m2/ha planned) and constructing roads (336 m2/ha unplanned vs. 203 m2/ha planned).
· Measures to reduce damage .
·
VINE CUTTING two years prior to cutting - vines cause damage when trees are
felled (i.e., tree felled pulls over trees linked or at least breaks part or
most of crown) and during road build with the bulldozer.
· Average gap size
in planned harvesting 166 m2 while in unplanned
logging 355 m2 (the average gap size for natural
tree falls in the region is about 200 m2).
·
Almost as cost effective as directional felling.
· DIRECTIONAL FELLING
results in less damage to residuals and less tangling of felled trees, which in
turn results in less tractor movement in the stand to untangle the logs
· The
most cost effective mitigating technique.
· USE OF SKIDDERS results in less
damage because narrower (3 m vs. 3.4-3.6 m in study) and less disruptive to the
soil surface.
· A skidder with a winch can also cut down on the amount of
vehicle movement in the stand.
· However, if the bulldozer has a winch there
is less area traffic in planned logging since the skidder requires a larger area
to turn around (i.e., bulldozer can do a 360 degree turn).
· My comment -
this can be fixed by fewer turn-arounds and turning into the corridor from which
the log(s) are being winched.
· PLANNING AND LAYOUT OF SKID TRAILS with the
trails in a herring bone fashion with main and secondary trails reduced the
amount of trail in the stand.
· In unplanned logging the bulldozer operator
basically just wandered through the forest.
· Also skidding shorter pieces
results in less damage to residual trees through rubbing.
· LANDING
CONSTRUCTION - in planned logging the amount of timber is known and the landing
the wood will be skidded to is known. Therefore, the landing can be made to the
size required, otherwise they are generally made too large.
· With planned
harvesting the second harvesting intensity will more or less be the same as the
first (38 m3/ha), while with unplanned
harvesting it is estimated to be 17 m3/ha, on a
30 year logging cycle.
· The most important component of improved forest
management programs is to reduce logging damage in selection/selective
cuts.
· Planning component in planned harvesting = $72/ha.
· Logging
efficiencies improved through sawyer finding trees quicker, skidder locating
trees, skidding to landing - these efficiencies gain back about 13% of the
planning cost.
· Also decreases costs by reducing the amount of waste and
lost wood - by reducing the stumpage value per m3 of harvested timber planned logging gains back
another 91% of the planning cost.
· In the short term 25.4% of the harvested
volume was wasted in the unplanned logging operation, through poor cutting
techniques or lost logs.
· The authors feel that overall profit will be
increased based solely on the short term costs.
· However, also need to look
at the long-term yield from the forest.
Jonkers, W.B.J. and P. Schmidt. 1984. Ecology and timber production in tropical rainforest in Suriname. Interciencia 9(5): 290-297.
· Growth rates in plantations in Suriname have not met
expectations.
· Plantation forests should only be put in places where the
forest has already been destroyed.
· If tropical rainforest have to be used
economically, other yield systems more adapted to the ecological conditions have
to be developed and used (e.g., CELOS).
· Commercial species accounted for
117.1 stems/ha (BA=10.11 m2/ha) (dbh >=10
cm).
· All species accounted for 476.9 stems/ha (BA=25.2 m2/ha) (dbh >=10 cm).
· Describes the use of
conventional unplanned logging and the associated problems.
· After logging
the most likely impression of a visitor, walking on a skid trail shortly after
logging, is one of almost complete destruction.
· In Suriname the logging
intensity rarely exceeds 20 m3/ha and the damage
is considerable, but the forest is not destroyed.
Jonkers, W.B.J. and J. Hendrison. 1987. Prospects for sustained yield management of tropical rainforest in Suriname. In: Proceedings of Management of the Forests of Tropical America: Prospects and Technologies, San Jan, Puerto Rico, September 22-27, 1986. USDA, Forest Service, Southern Forest Experiment Station. p.157-173.
· Diameter growth in recently logged forest (trees dbh
> 15 cm) was 0.43-0.52 cm/year, compared to 0.36 cm/year in unlogged
stands.
· In Suriname logging intensity seldom exceeds 20 m3/ha (1986).
· Logging damage with mapping of
stems for felling only to avoid needless tractor driving within the stand (main
experiment near Kabo, Suriname). Number of stems/ha and logging damage to
commercial species only:
|
Stems/ha |
Percentage per damage category | |||||
|
Felled |
Destroyed |
Injury |
No damage |
Total | ||
|
Level of exploitation: 15 m3/ha | ||||||
|
5-15 15-35 35-65 >65 >15 |
87 51 35 9 182 |
0.0 0.0 4.4 20.4 1.9 |
12.2 7.4 4.3 0.5 8.7 |
2.6 9.9 12.8 13.5 7.1 |
85.2 82.7 78.5 65.6 82.2 |
100.0 100.0 100.0 100.0 100.0 |
|
Level of exploitation: 46 m3/ha | ||||||
|
5-15 15-35 35-65 >65 >15 |
77 50 34 8 169 |
0.0 0.0 22.7 48.5 6.9 |
25.0 13.8 7.9 4.2 17.3 |
5.8 16.5 14.6 14.2 11.1 |
69.2 69.7 54.8 33.1 64.7 |
100.0 100.0 100.0 100.0 100.0 |
Jonkers, W.B.J. and van Leersum, G.J.R. 2000. Logging in south Cameroon: current methods and opportunities for improvement. International Forestry Review 2(1): 11-16.
· The study area is located on poor soils on the Central
African Shield.
· The current basal area is 34m2/ha; the felling intensity varies from 0.3 to 1.8
trees/ha.
· 5.1% of the harvested area incurred disturbance caused by logging
(felling 1.4%, skidding 1.1%, road and landing construction 2.7%).
·
Approximately 30% of the damage due to roads and landings could have been
avoided.
· About 20% of the skidding damage (e.g. dual trails, shortcuts)
could have been avoided.
· The volume delivered to the sawmill was 70% of
the amount felled. Losses occurred during felling (21%), topping (7-10%), logs
not found (4%) and cutting off both ends of the log to give the timber a better
appearance (4%).
· Liana cutting did not have a noticeable effect on logging
damage.
· Directional felling did not reduce the damage to trees of
commercial interest significantly.
· Skidding restrictions following rain
also reduced damage, but lead to losses of output in all production phases. This
may outweigh the benefits.
· About 20% of the harvesting damage could have
been avoided using the full range of RIL elements (4 instead of 5% of the
residual stand damaged).
Jonsson, T. and P. Lindgren. 1990. Logging technology
for tropical forests - for or against? Forskningsstiftelsen Skogsarbeten, Report
to the ITTO. 126pp.
· The report on the state of logging in the moist
tropical forests based on a literature review and site visits.
· Logging is
an integrated part of forest management; the way it is planned and executed
affects both short- and long-term revenue from forestry.
· In the immediate
future, it is more important to improve the use of available logging equipment
than to develop new equipment.
· Frequency and intensity of logging are as
important as the choice and use of equipment.
· Integrated forest enterprises
involved in both logging and wood processing are most likely to take a long-term
interest in forest management.
· Tropical moist forests (TMF) can be
sustainably managed for timber and non-timber products; however, systems for
sustained management of TMF are rarely implemented in practice.
· Many of the
aspects of logging are not complicated; all that is needed is a little
theoretical background and some down-to-earth practical work in the field along
with common sense.
· RIL methods are well known but are not widely applied
because of:
short term aims, and lack of planning and control
many forest operations focus on current cost minimization and profit maximization without consideration of the future
concession agreements, incentives and payment schemes do not stimulate sustained yield management and in fact often encourage the opposite
profit levels in tropical forestry have in many cases been extremely high, and thus the interested parties have been "spoiled" and are reluctant to accept any reduction in short term profit
knowledge acquired throughout research has not been broadly disseminated
· Survey results on what the forest authorities regard as most urgent to improve if sustainable forest management is to be achieved:
|
Responses out of a total of 95 | |
|
Better land use policies and plans More serious enforcement of existing laws and regulations Efficient control Funds for forestry authorities Better long range planning Better planning prior to logging Better training Better recognition of the importance of the tropical forest Better concession agreements Proper and distinct laws Better and more suitable machines |
12 11 11 10 9 9 9 7 7 6 4 |
· Survey showed that the most widely used logging
systems employed bulldozers or bulldozers in combination with skidders.
· A
large number of forest industries can still afford to run inefficiently because
of low log prices and easily available raw material. The equipment used is often
of inferior quality and wastage is high. The export market has only accepted the
highest qualities of timber and selected species and little has been done to
change this.
· Industry is starting to realize the benefits of integration
where there is tremendous scope for improvement.
· Formal vocational training
in timber harvesting for forest workers exists only in a few places in the
tropical world and only a couple of these training centres offer courses on a
regular basis.
· To achieve more efficient and environmentally sound logging
practices, training is urgently needed; if logging training is not given a
higher priority; very little progress will be achieved in improving forest
management and environmental protection.
· Ergonomics and work safety are
central in forestry and harvesting but are grossly neglected.
· The great
majority of loggers pay very little attention to the ecological consequences of
their operations.
· 11 out of 13 responses from countries viewed current
large scale logging practices as unsatisfactory in regard to sustainable
management.
· The forest enterprise should either own the forest land or have
its concession granted on a long-term basis; i.e., substantially longer than one
cutting cycle and in such a way that retention of the concession is guaranteed
as long as the conditions of the agreement are met.
· Felling is the most
crucial phase of the operation because it influences efficiency, logging costs,
the value of timber and silvicultural results.
· If the bulldozer is
over-sized there is a temptation for the operator to use power instead of skill,
while if the bulldozer is under-sized too much winching and equipment
maneuvering, and thus increased cost, can result.
· A compartment within a
concession should be logged at one occasion only and then closed off to allow
the forest to recover (30-40 years). Re-entry, after a short time, to harvest
another species should be prohibited.
· Can reduce costs and impacts by using
more species, but only up to a point that the stand can recover from
efficiently.
· Should be better use of the resource at the stump and at the
mill.
· Theoretical simulations of cost and yield showed a 20% reduction in
cost through improved logging practices, while 5 m3/ha or 7% more volume (based on a logging intensity
of 60 m3/ha) could be extracted through improved
felling and bucking techniques.
Karsenty, A. 1998. The economic implications of reduced impact and conventional logging. In: Silvicultural research in a lowland mixed dipterocarp forest of East Kalimantan. Cirad-foret. 1998.
· The data for this study was collected from the STREK
project in East Kalimantan (Indonesia).
· Efficiency and costs of intra-plot
skidding:
|
Treatment |
Volume extracted (m3/h) |
Costs ($/m3) |
Costs of trails ($/km/m3) |
|
RIL _50cm |
48.42 |
2.95 |
7.38 |
|
RIL _60cm |
46.53 |
3.14 |
11.25 |
|
Conventional |
35.65 |
4.03 |
7.20 |
· It was estimated that the additional costs of the
engineering needed for pre-planning and supervision of improved management
should not exceed US$ 20 to US$ 25 per hectare.
· The cost-benefit analysis
indicates that US$ 50 to US$ 74 can be saved per hectare with improved
management.
Kartawinata, K. 1978. Biological changes after logging in lowland dipterocarp forest. BIOTROP Special Publication 3: 27-34.
· With a log extraction intensity of 25 trees/ha in an East Kalimantan forest it was found that the tractor paths amount to about 30% of the ground surface.
Kasenene, J.M. and P.G. Murphy. 1991. Post-logging tree mortality and major branch losses in Kibale Forest, Uganda. Forest Ecology and Management 46(3-4): 295-307.
· Annual rates of live tree falls per hectare were 1.30
lightly cut (14 m3/ha), 3.30 heavily cut (21
m3/ha and extraction tracks heavily disturbed),
and 1.74 for uncut mature forest.
· Medium altitude tropical moist
forest.
· In the utilization of tropical moist forest, emphasis should always
be put on low disturbance levels similar to the natural rate of tree falls that
form an integral component of the mature forest dynamics.
Kelvin, A. 1993. Estimate of timber production, capacity utilization and export potential in Zaire. Commonwealth Forestry Review 72(3): 175-180.
· The yield of exportable species in Zaire is limited
for marketing and ecological reasons to 6-10 m3/ha on a 25 year cutting cycle; e.g., in the
Atlantic province of Bas Zaire, where the forests have been creamed.
·
Experts interviewed believe that new concessions in other provinces deeper in
the hinterland can yield 20-22 m3/ha.
· If
all species currently used by foreign and home markets are taken into
consideration the yield (according to those interviewed) could reach 50 m3/ha.
· With promotion of additional species the
yield could be further increased to 60-70 m3/ha.
· There is no scarcity of forest reserves;
the question is how to put forest resources to good use.
Kilkki, R. 1992. Reduction of wood waste by small-scale log production and conversion in tropical high forest. Food and Agriculture Organization of the United Nations, Forest Harvesting Case Study 1992:1. 33pp.
· Studies by FAO have shown that nearly half of the
timber volume felled during commercial harvesting operations in tropical forests
remains in the forest as unutilized residues after the loggers have
departed.
· Papua New Guinea:
after commercial logging 60 m3/ha of merchantable size standing timber left, plus 30 m3/ha of uncommercial mature trees
volume of trees damaged during traditional logging operations and left in the forest was found to be about 15 m3/ha in size classes from 20-50 cm dbh (i.e., 17% of total volume)
the number of stems damaged (dbh >20 cm) was 229 of the 673 residual trees or 34%
10.35% of the export volume was left at the harbour as not fulfilling export grading rules
uses a vertical circular saw 32 inches in diameter and a horizontal 12 inch diameter saw
annual roundwood production of 5 million m3 from 80 000 ha (62.5 m3/ha calculated logging intensity).
50 cm minimum dbh (60 cm minimum dbh for companies exporting logs)
skill of the sawmilling crew is imperative in recovery and quality of product
logging intensity is 5-8 stems/ha or 30 m3/ha on average
average portable sawmill recovery was 52% (44-56% range)
Klassen, B. and J. Cedergren. 1996. Felling the right way. ITTO, Tropical Forest Update 6(3): 5-7.
· Directional felling is done to minimize damage to the
log, minimize damage to the residual stand, and to facilitate log
extraction.
· Direction felling is more time consuming than haphazard
felling, but gains in these three areas will almost certainly outweigh the
costs.
Kleine, M. and J. Heuveldop. 1993. A management planning concept for sustained yield of tropical forests in Sabah, Malaysia. Forest Ecology and Management 61(3-4): 277-297.
· In many regions of the tropics, forest managers are
today confronted with the situation that the natural primary forests have either
already disappeared or will do so in the very near future.
· Left over are
residual forests which are considerably different to the primary forests in
respect of species composition, structure, dynamics and ecological
stability.
· Of fundamental importance to change from pure exploitation of
the forest to sustainable forest management practice.
· Failures in tropical
forest management are mainly due to the lack of proper enterprise management, as
well as to unfavourable macro-economic framework conditions.
· One of the
issues most intensively discussed among forest managers ins the estimation of
the volume of timber which can be harvested on a sustainable basis.
· An
example of a production goal applicable to the present condition of a
logged-over lowland dipterocarp forest is Sabah is: local tropical hardwood/high
value product; 15-30 trees/ha >60 cm dbh of light and medium hardwood
dipterocarp and non-dipterocarp; more than 50% veneer quality; uneven-aged
structure.
· Based on silvicultural experience in Sabah, a dipterocarp stand
can produce 15-30 trees/ha (>60 cm dbh) of marketable timber species at the
end of a cutting cycle, average tree size of 3 m3, gives 45-90 m3/ha.
· The cost for medium-term management
planning is 14 USD/ha or 0.70 USD/ha/year on a 20 year management planning
period.
Korsgaard, S. 1985. Guidelines for sustained yield management of mixed dipterocarp forests of South East Asia. Food and Agriculture Organization of the United Nations, GCP/RAS/106/JPN, Field Document 8. 78pp.
· Based mainly on work in Kuching, Sarawak,
Malaysia.
· At present the sustainable level of production is estimated at 2
to 3 m3/ha/year of net industrial volume of
desirable species over 30 cm dbh.
· After a period of 40 years the
accumulated production should be about 80 m3/ha
of which 50% can be utilized. The average net industrial volume possible to take
out after 40 years will be about 40 m3/ha, which
is at a level equivalent to that of the initial harvest.
· This paper
outlines RIL.
· Mono-cyclic systems have a rotation length of 70 to 80 years,
are expensive and ecologically less desirable.
· Poly-cyclic systems have a
cutting cycle of 35-40 years, concentrate efforts where the highest returns can
be expected and the system is ecologically acceptable.
· In many cases half
or more of the trees remaining after logging are damaged, some of them so badly
that they will die.
· The area lost to roads, landings and trails varies
considerably depending on the terrain, the harvesting system and the individual
operator. Currently, as a rough estimate, at least 10% of the area is lost and
must be deducted from the productive forest area.
· Few secondary forest
areas have been left undisturbed sufficiently long to yield conclusive evidence
of the attainable level of production; indications are that the production is
around 1.5 3.0 m3/ha/year.
· In one example
of RIL in Sarawak the residual stand consisted of 380 trees/ha (21 m2/ha of basal area), which was sufficient to produce
a second crop in 35 to 40 years time.
· The problem in many cases is that
when the market picks up many of the trees left after the first logging become
profitable to extract. Re-entering the forest causes heavy damage to the young
seedlings and saplings. By repeated re-entering the forest is gradually damaged
beyond the level where it is able to regenerate natural. The relogged forest
often deteriorates into a state of unproductive weeds.
· Unfortunately many
of the dipterocarp forests in Southeast Asia have been badly damaged by logging
disregarding the fact that wasteful and damaging harvesting is more expensive
and at the same time gives a lower rate of production than does a well planned
and carefully supervised harvesting operation. Careful harvesting extracts more
of the felled trees and leaves a less disturbed forest with greater potential to
rehabilitate itself.
· The conclusion is: there is no reason to tolerate
harvesting operations that are wasteful and damaging.
Kramer, R., R. Healy and R. Mendelsohn. 1992. Forest valuation. In: Sharma, N.P. (ed.). Managing the World's Forests. Kendall/Hunt Publishing Co., Dubuque, Iowa. p.237-269.
· Under-valuation of forests has caused governments to assign a low priority to the forestry sector because of its apparently low contribution to gross national product (GNP).
Kuusipalo, J., Kangas, J. and Vesa, L. 1997. Sustainable forest management in tropical rain forests: A planning approach and case study from Indonesian Borneo. Journal of Sustainable Forestry 5(3/4): 93-118.
· The study area is located in South Kalimantan.
·
The average volume of marketable tree species with a diameter >50cm is
120m3/ha.
· A harvesting intensity of 40m3/ha is possible if a 35-year cutting cycle is
applied.
Lamprecht, H. 1993. Silviculture in the tropical natural forests. In: Pancel, L. (Ed.), Tropical Forestry Handbook. Springer-Verlag, Heidelberg, Germany. p.728-810.
· In the tropics proper forestry and silviculture are
the exception.
· Only 1-5% of the topical forests are under sustained-yield
management.
· The preservation of the tropical rain forests seems only
possible by replacing the traditional wasteful methods of need satisfaction with
usage that is based on sustained yields.
· The necessary basic knowledge, as
well as suitable silvicultural technologies, are available.
· These are
outlined in the chapter.
Laurance, W.F. and S.G.W. Laurance. 1996. Response of five arboreal marsupials to recent selective logging in tropical Australia. Biotropica 28(3): 310-322.
· Selective logging of topical rain forest in
Queensland, Australia.
· 150 ha site in which an average 8-10 trees/ha were
removed (50-55 m3/ha) in 1987-1990.
· Site
had been lightly logged in the 1920's with bullock teams.
· 14 species
comprised 95% of the volume, and 4 species comprised 50% of the volume.
· In
previously logged areas (1979-1980) the logging intensity was 34.4 m3/ha.
Lee, H.S. 1982. The development of silvicultural systems in the hill forests of Malaysia. Malaysian Forester 45(1): 1-9.
· In the hill forests of Sarawak the number of trees/ha
removed varies from 4 to 20.
· The average logging intensity (1974-1978) was
25 m3/ha, with the standing volume being 94-145
m3/ha.
· Planned logging cycle is 25 years,
but the author doubts this short of a cycle is appropriate, especially due to
the high damage factor that must be accounted for.
· Lack of planned skidways
in the forest leads to the creation of numerous tractor paths for seeking
logs.
Leslie, A. 1977. Where contradictory theory and practice co-exist. Unasylva 29(115): 2-17.
· As a general rule logging costs generally account for
25-35% of the price of processed wood.
· It is fairly common experience to
fine logging costs in tropical forests varying by as much as 50% between
operators.
· Quite often, inefficiencies in logging are the result of
anachronistic and badly administered procedures and regulations, or of lax
supervision and control measures.
Leslie, A.J. 1987. A second look at the economics of natural management system in tropical mixed forests. Unasylva 39(155): 293-295.
· prominent feature of tropical forest management is the
limited success of natural management systems - more often than not, this lack
of success is the result of no management at all, rather than the failure of
natural management
· the tropical moist forest can survive only if the land
itself is seen by the people concerned to be more valuable retained as forest
than converted to any other form of land use
· natural management of the
tropical mixed forest, wherever it is ecologically feasible, is also, on its own
merits economically preferable
Lindgren, P. 1992. Just beyond the obvious. In: Beyond the guidelines - an action program for sustainable management of tropical forests. International Tropical Timber Organization, Technical Series No. 7. P.37-45.
· The vision - we want machines that do not waste or
destroy, either nature or the operator.
· The vision - felling a tree without
damage to the remaining stand, or to the tree itself or the operator. Or
machines with high traction, high ergonomic standards, low ground pressure, good
manoeuvrability, a high payload and which are easy to service and operate, and
low price.
· The vision - on the human side there is planning, organization,
leadership, education, teamwork, well-being, nourishment, incentives, etc.
·
The following are possible and occur in the topics - tropical forests can be
used for many purposes (only one is timber production)/sustainable management is
possible/logging damage can be reduced and efficiency improved/harvesting
equipment and knowledge of how this equipment should be used is already to a
large extent at hand.
· Why not implemented, because - actual targets are
cost minimization and profit maximization/incentives and payment schemes are
constructed so as to effectively sustain these targets/short-term
thinking/concessionaires and loggers and sometimes industry are separate
entities/profit levels have often been so high that any adjustment towards less
is regarded as highly disadvantageous.
· Technical adaptations must be
coupled with changes to the institutional framework and intensified training and
education. It is the way the equipment is used that causes the greatest damage -
it is the malpractice more than inadequate equipment that causes the greatest
adverse effects. At the same time there are simple technical things that are
neither known, nor used.
· Loggers are often ignorant and are not aware of
how the economy of their operations benefits from using more efficient and
better adapted machines and work methods.
Loehnertz, S.P., I.V. Cooz and J. Guerrero. 1996. Hardwood sawing technology in five tropical countries. Forest Products Journal 46(2): 51-56.
· Countries studied were Ghana, Brazil, Venezuela,
Indonesia and Malaysia; account for about 21% of the world's total hardwood
sawnwood.
· Knowing how to efficiently process its wood enhances present and
future value of the forest.
· Sawmill recovery for U.S. hardwood mills is
likely in the range of 45 to 55%.
· Sawmills in tropical countries will more
likely process larger diameter logs (yield should be higher).
· In Africa
more than 90% of the sawing machines are bandsaws.
· In Ghana, lumber is not
planed and average yield is 40%, increasing to 50% in the best case.
· Many
reported problems in Ghana are related to maintenance (e.g., saw being used when
dull, gullet burn while sharpening, incorrect and uneven tension, uneven crown,
burrs left in gullet when sharpened, faulty wheel bearings, saw too thick for
wheel dimensions and bandmill vibration). Lack of skilled labour and management
is partly to blame.
· In Brazil there is highly selective forest
exploitation, scarcity of qualified personnel, and obsolete equipment and
inadequate maintenance structure.
· Maranhao State (Brazil) the lumber
recovery from three Cikel Sawmills (bandsaw mills) was about 55%, with only part
of the mill production being planed.
· In Para the wood is harder and of
higher moisture content than in other parts of Brazil, and recovery can be very
low at 20% (80% fibre loss with 60% lost in the forest and another 20% in the
mill).
· In Venezuela almost all sawmills use bandsaws and the usual recovery
from a sawlog is 60 to 70% in sawnwood of commercial dimensions; the value seems
unusually high, but the basis of computation is unclear.
· In Indonesia, the
waste from logging may exceed the log volume extracted, perhaps by 1.5 to 2
times, when considering damage to the stand and the full range of log diameters
(Mordeno 1990).
· In Indonesia, problems that have contributed to the low
performance of the industry (yield less than 50%) include inefficient production
techniques and machinery, lack of skilled labour and poor managerial
skills.
· In Malaysia bandsaws are almost exclusively used, and throughout
the industry the average recovery rate is 54.5%.
· In general, the density of
wood and occurrence of silica make it a challenge to saw many tropical
hardwoods, and the most commonly reported sawmill problems include poor
maintenance, lack of trained personnel, obsolete equipment, and inadequate
sawtooth geometry and wear resistance.
Lowe, R.G. 1978. Experience with the shelterwood system of regeneration in natural forest in Nigeria. Forest Ecology and Management 1(3): 193-212.
· Paper outlining the Nigerian Tropical Shelterwood
System and its history.
· This was the dominant method used until the 1960's
when there was a change in emphasis to artificial regeneration.
· However,
still most of the volume was from natural forests.
· Natural forests are not
adapted to withstand heavy exploitation or to maintain high increments.
· For
this reason the author saw the need to change to intensive plantation forestry
to supply the fibre needs.
· Also it was noticed that the success of the
system probably depended more on advance growth than on regeneration stimulated
by the shelterwood operations themselves.
· The increment for the natural
forest is about 2 m3/ha/year.
· On average
less than 20 trees/ha with dbh >50 cm.
· On average 5 trees/ha (dbh >80
cm for some species) were utilized.
· Logging intensity in the 1940-50's was
less than 20 m3/ha, compared to a total stem
volume >200 m3/ha.
· Logging intensity has
increased.
· With current methods, the total exploitable volume averages
about 100 m3/ha of which 30 m3/ha is actually extracted, on a cutting cycle of 50
years (was reduced from 100 years).
· Total volume in stems >40 cm dbh was
100 m3/ha, and for trees >60 cm 75 m3/ha.
· A growth rate of 15 m3/ha/year with a total exploitable volume of 300
m3/ha is given for plantations.
Lowe, R. 1992. Volume increment of natural tropical moist forest in Nigeria: a preliminary account of the high forest monitoring project. In: Beyond the guidelines - an action program for sustainable management of tropical forests. International Tropical Timber Organization, Technical Series No. 7. P.150-151.
· Study of five high forest reserves in different
climatic/geographic regions of Nigeria.
· Mean annual increments for bole
volume were about 5.0 m3/ha/year plus or minus
1.0 m3. This included 2.5 m3 for exploitable species and 1.2 m3 for veneer quality species. Standing bole volumes
ranged from 110 to 340 m3/ha, and standing basal
areas from 16 to 37 m2/ha. Exploitable species
accounted for about half the total standing volume of the forest.
· The
results suggest that the forests can withstand removals from an annual coupe
equivalent to 50 m3/ha of the standing bole
volume on a 25 year felling cycle (35 m3/ha in
terms of log removals) without serious damage to the forest - although the
relative proportions of species may change as a result of repeated
exploitation.
· Necessary to set minimum felling diameters for the various
species.
· For example, in species valued for decorative wood, such as the
mahoganies, the heartwood is coloured whereas the sapwood is white and is less
durable than the heartwood; moreover, larger trees put on proportionately more
wood for the same diameter increment besides being the main seed bearers.
·
Some species requiring a minimum felling diameter of as much as 80 cm or 90 cm,
while other species do not grow to large sizes, and require lower minimum
felling diameters of perhaps 40 cm DBH.
· The length of felling cycles is
limited by a minimum period which allows the weed growth following exploitation
to be shade out (perhaps 15 years), but not so long that exploitable trees are
lost due to over maturity.
· However, the present situation in Nigeria is
that none of the high forest reserves are currently being managed under working
plans, and exploitation is scarcely regulated - and is proceeding to an extent
that is destroying the recuperative capacity of the foret. This extends to
secondary forest products that are garnered in the forest, such as chewsticks,
wrapping leaves, spices, medicinal materials and bush meat. These are important
for the livelihood of local communities and need to be brought within the ambit
of the forestry working plan.
Macedo, D.S. and A.B. Anderson. 1993. Early ecological changes associated with logging in an Amazon floodplain. Biotropica 25(2): 151-163.
· A study of selective logging of high density virola
(Virola surinamensis (Rol.) Warb.) stands in the basin of the Rio Preto
(Amazon).
· Charcoal deposits in the area suggest that the currently high
density of virola could be indicative of old successional forest (major fires in
region in early 1900's).
· First logging started with removal of larger trees
>45 cm dbh for plywood production, followed by sawmillers removing material
under 30 cm dbh.
· Floodplain logging in the area is manual; axes are used
for felling and cross-cutting.
· Wood is floated out along hand-dug canals
during the wet season.
· In other floodplain areas inventories have shown an
average density of 10 virola trees/ha with dbh >= 15 cm, however, in the
study area it was 265 virola trees/ha with dbh >= 15 cm.
· Most logging
impacts appear to be concentrated along a narrow strip (average 73 m) of forest
adjacent to the canals, however, secondary canals extend the impact each
year.
· First the larger wood was removed, followed by successive removal of
smaller material.
· After 5-years of logging the understory consisted of a
dense secondary community dominated by vines and herbs.
· Inventory of the
area found that the bole volume of virola (dbh >= 5 cm) was 243 m3/ha (62% of the bole volume for the entire swamp
forest).
· Virola trees with diameters as low as 26 cm are harvested.
· It
was estimated that 145 m3/ha of virola are
extracted under current logging operations. To harvest that wood, loggers must
fell a total volume of 218 m3/ha or 90% of the
virola stand and at least 56% of the entire swamp forest. Due to inevitable
damage to the residual stand the 56% of the entire forest is an
underestimate.
· Brazils environmental regulatory agency, IBAMA, stipulates a
minimum diameter limit of 29 cm for marketed virola logs and minimum felling
diameter of 45 cm dbh.
· Log checks found that 22.1% of the logs were below
the legal limit and it was estimated (based on form factors and regressions)
that 70% of the felled trees would be below the minimum tree size.
·
Reference to Rio Mocoòes (Uhl 1990) where logging intensity was 5 m3/ha and 10% of the remaining trees were damaged in
the removal of virola in a swamp forest and thus low impact with good
regeneration and sustainability (unless the sawmillers move in and start
removing the smaller pole-size material).
· In the case of this study the
logging was unsustainable due to high logging intensity; after the first year of
logging virola's basal area plummeted from 24.6 m2/ha to 2.3 m2/ha,
and over a five year period seedling density per m2 declined from 2.3 (year 0) to zero (year 5).
·
Like previous economic booms in the Rio Preto, logging of virola is thus
destined to be a short-lived activity.
· Given virola's economic importance
and high potential under sustained yield management, its demise under current
logging practices is especially tragic.
· The log-size and minimum tree dbh
limits are impossible to enforce; e.g., the IBAMA station in the town of Breves
maintains only one forest guard responsible for the entire estuarine area.
Enforcement of forestry policies pertaining to virola, as well as to other
forest resources in the Amazonia, is woefully inadequate.
· In addition to
wood supply problems for the local industry, the demise of virola will lead to
increased pressures on a wider range of alternative forest resources, thus
exacerbating the ecological impacts of current logging practices in the
region.
Malinovski, J.R. 1996. Problems and chances for forest operations in Amazon Basin. In: Proceedings of Forest Operations for Sustainable Forestry, XX IUFRO, World Congress, August 6-12, 1995. IUFRO S3.05-00 and CIFOR Publication. p.47-49.
· A 100% inventory of trees >50 cm dbh in an Amazon forest, clay soils and slopes 0-25% yielded 18.7 m3/ha of commercial volume:
12.5 m3/ha of plywood logs
1.0 m3/ha of veneer logs
5.2 m3/ha of sawnwood
4.1 m3/ha of non-commercial species
· Paper outlines RIL techniques.
Malmer, A. and H. Grip. 1990. Soil disturbance and loss of infiltrability caused by mechanized and manual extraction of tropical rainforest in Sabah, Malaysia. Forest Ecology and Management 38(1-2): 1-12.
· New tractor tracks (D4 and D6 class crawler tractors)
cover 25% of the area in the mechanically extracted area.
· For the manual
extraction area (kuda-kuda) the area of skid trails was 4% of the area.
·
During rain the extraction stopped, and for heavy storms normally stopped for
one or two days due to the tracks being too slippery.
· Along the most
heavily used parts of the tracks, up to 1 m of the upper soil layers were pushed
aside.
· In some wet places, soil was bulldozed into them or new tracks were
established around them.
· In the top 10 cm, mean dry bulk density increased
after all treatments, but was significant only in the top 5 cm on clay soil
after tractor extraction (increased from 0.82 to 1.28 g/cm3).
Malvas, J.D. 1987a. Development of forest sector planning, Malaysia: logging. Food and Agriculture Organization of the United Nations, FO:DP/MAL/85/004, Field Document 6. 90pp.
· Contract fellers have scant regard to felling sequence
considerations or to damages to forest growth.
· To exceed their production
figures, tractor operators bulldoze their way often carelessly to felling
concentrations and thereby damage regeneration and the soil.
· Studies in
dipterocarp forests on logging wastes show that for every 100 m3 extracted, 80-105 m3 of logging wastes are left behind considering
materials with minimum dimensions
of 0.91 m long and 30 cm diameter (9.3%
stumps, 31.4% tops and branches, 2.3% end trims, 50% damaged residual trees and
abandoned logs).
· Weidelt and Banaag (1982) (note: could not find report)
studied logging damages in Mindanao , Philippines and found the following
tractor skidding damages:
|
Method of logging, damages and terrain conditions |
Residual dipterocarp, % |
Residual non-dipterocarp, % |
|
A. Tractor skidding - felling damages - skidding damages Total B. Highlead, rolling terrain - felling damages - yarding damages Total C. Highlead, rough terrain - felling damages - yarding damages Total |
13.1 22.1 35.2 16.7 38.7 55.4 14.1 52.0 66.1 |
53.3 58.0 62.3 |
Malvas, J.D. 1987b. Development of forest sector planning, Malaysia: a report on the logging demonstration cum training coupe. Food and Agriculture Organization of the United Nations, FO:DP/MAL/85/004, Field Document No. 7. 43pp.
· Study of RIL with tractor skidding and highlead
yarding to demonstrate the potential benefits through reduced destruction to
residual and environment, and cost effectiveness.
· RIL must ensure that an
adequate number of 20-60 cm dbh trees/ha are retained in a healthy state after
logging through the implementation of selection logging techniques.
· In
ground skidding area 89 m3/ha available for
harvest.
· Optimum feeder road density was 12.5 m/ha (i.e., road spacing 800
m = average skid distance 400 m (straight-line)).
· 70.42 m/ha of skid trails
laid out (width D7 blade width of 4.17 m + 0.5 m = 4.67 m) and covered 3.3% of
the area.
· Optimal (i.e., minimum) total area covered by roads, landings and
skid trails slightly over 5%.
· Comparison of the number of advanced
regeneration left per hectare after logging with supervised (48 ha) and
unsupervised (21 ha) felling (tractor skidding):
|
Dbh classes |
Supervised felling |
Trees/ha remaining | |
|
Trees/ha marked for retention |
Trees/ha remaining after logging |
after unsupervised felling | |
|
20-29 30-39 40-49 50-59 60-69 Total |
9.16 6.83 2.29 3.26 1.56 23.10 |
6.42 5.48 2.86 2.64 1.58 18.98 |
5.88 2.79 2.46 1.12 - 12.25 |
· An accurate topographic map with 5-10 m contour
interval will speed up planning and layout of skid trails.
· The use of
felling tools is a prerequisite for successful implementation of directional
felling.
· Tree marking as a selective logging activity is futile without
directional felling.
· Directional felling saves more crop trees than the
uncontrolled operation (19/ha vs. 12/ha).
· Bucking length instructions
imposed in the woods definitely increases log utilization efficiency of wood
processing mills, however, odd length logs could be left in the woods.
·
Utilization of the tractor skidder was only 62% of an eight hour day.
Margules, S.R., D. Nelson, T. Petr, A. Ravuvu, U.
Sundberg and R. Watling. 1987. Study of the environmental impacts of logging:
Navua-Navutulevu Concession Area - Vitilevu. Food and Agriculture Organization
of the United Nations, TCP/FIJ/6652, Field Document 1. 108pp.
· Mini-EA
study of logging in a concession in Fiji.
· Logging intensity is 40-50 m3/ha (min. dbh 35 cm), from a total wood biomass
estimated at 250 m3/ha (minimum dbh not stated
but assumed to be 10 cm).
· 30-40 years given as the period for logging all
natural forest on the concession.
· Assessed disturbance 62% of area (light
disturbance 45%; heavy disturbance, skid tracks and skid roads 12%; and landings
and roads 5%).
Marsh, C.W., J. Tay, M.A. Pinard, F.E. Putz and T.E. Sullivan. 1996. Reduced impact logging: a pilot project in Sabah, Malaysia. In: A. Schulte and D. Schöne (eds.). Dipterocarp Forest Ecosystems: Towards Sustainable Management. World Scientific Publishing Co. Pte. Ltd., Singapore. p.293-307.
· An essential requirement for sustainable forest
management of tropical forests is a selective harvesting system that minimizes
incidental damage to the residual stand and soil.
· Important in RIL are
pre-harvest planning including preparation of a large scale stock/terrain map
(1:5000), advance vine cutting, directional felling towards pre-planned skid
trails, and above all, close supervision of tractor operations, so as to
minimize skid trail length and blade use (also need to use the winch).
·
After logging the area must be closed from further operations and skid trails
rehabilitated.
· Post harvesting monitoring of success/failure of logging
operations is a component of RIL.
· Research plots demonstrated more than 50%
reduction in all measures of damage compared with conventional logging for an
increase of about 10-15% in direct logging costs.
· Restrictions on
wet-weather skidding slowed harvesting operations considerably in RIL areas and
added to the cost.
· Additional considerations are the needs for training,
operational stoppages after heavy rain, and the opportunity costs of retaining
trees on very steep slopes and along riparian reserves.
· RIL not only
minimizes all external environmental costs but also assures greatly improved
future harvests with little or no need for further silvicultural treatment.
·
In regard to timber certification, RIL opens the possibility of additional
market-related benefits.
· Study area was 1400 ha.
· By Federal Government
mandate from 1984, all forest reserves in Sabah are supposed to be managed on a
sustainable basis. In practice, little evidence exists to suggest that this is
the case.
· In eastern Sabah the average log weighs 7-9 tons and 80-100 m3/ha are extracted.
· In the RIL logged area skid
trail area averaged 3.4% of the area, compared to 12% in adjacent conventional
logging areas, of which 38% of the skid trails in the RIL area has subsoil
exposed, while in the conventional area 87% of the skid trails had subsoil
exposed.
· Timber volumes extracted and logging damage in Sabah,
Malaysia. Mean values (with standard deviations) from four logging units of each
logging method:
|
Conventional logging area |
Reduced impact logging area | |
|
No. of trees extracted per ha Timber volume extracted, m3/ha Percent of area with soil disturbance Skid trail density, m/ha Percent of trees killed during logging (5-60 cm dbh) Density of undamaged saplings (5-20 cm dbh) per ha |
13.6 (2.7) 139 (23) 17 (2) 199 (36) 41 (11) 49 (24) |
8.8 (3.6) 103 (54) 7 (3) 67 (26) 15 (7) 104 (62) |
· Four types of costs associated with RIL:
direct costs from more careful planning, climber cutting, tree marking, directional felling, better road construction standard, etc.; as RIL becomes more common these costs may add 10% to the direct operating costs
cost associated with the need for prior training and research required for the introduction of RIL
indirect cost due to weather delays when men and equipment are idle for 24 h after a heavy downpour
indirect opportunity cost of not extracting timber on steep slopes, although these areas could be reserved for logging with skyline or helicopter logging systems
· There are also cost savings in RIL; bulldozer
maintenance and operating costs reduced, skidding production increased.
·
There is the longer-term cost saving in silvicultural inputs and
increased/maintained timber yields in the future.
Martini, A., N. Rosa and C. Uhl. 1994. A first attempt to predict Amazonian tree species threatened by logging activities. Environmental Conservation 21(2): 152-162.
· Summarizes information on ecological characteristics
of 305 timber species in Brazilian Amazon.
· Developed a scoring system to
rank species with regard to their hypothesized ability to withstand logging
impacts.
Mason, D. 1996. Responses of Venezuelan understory birds to selective logging, enrichment strips and vine cutting. Biotropica 28(3): 296-309.
· Humid evergreen tropical forest with a canopy that
varies from 30-35 m with emergents reach 50 m in height.
· Although 37
commercial species in the area, 75% of the volume extracted was "mureillo" (Erisma uninatum, Vochysiaceae).
· Minimum felling
dbh is 40 cm.
· Felling with chain saws and extraction with skidders.
·
For 1988-93 2.9-7.3 trees/ha (5.8-14.2 m3/ha)
were authorized for extraction, however, the actual extraction rate was lower
and reached 2.3 trees/ha (7.1 m3/ha).
· Tree
basal area in unlogged forest was 32 m2/ha,
logged 23 m2/ha and logged with linear strip
planting 20 m2/ha.
Masson, J.L. 1983.
Management of tropical mixed forests: preliminary assessment of present status.
Food and Agriculture Organization of the United Nations, Mimeograph
FO:MISC/83/17. 54 pp
· Maintenance of the ecological balance of the forest
ecosystems in many instances has been more or less disregarded, mainly due to
inadequate knowledge of the systems and of the silvicultural requirements of
many of the species that compose the tropical mixed forest.
· Tropical forest
management started in India and Burma more than a hundred years ago.
· Today
only 4.4% of the tropical closed production forest is reported to be under
management (which does not mean that intensive high yielding systems are
used).
· Taking into consideration the relatively long time it takes most
timber species to reach maturity there really has been little time to develop
viable management systems for the complex tropical mixed forest.
· Stands
containing more than 150 different species of trees on a single hectare are
common in some tropical forest types and even in comparatively simple forest
types in the tropics it is not unusual to have 30 species occurring in intimate
mixture on a single hectare ... compare this to Sweden which has some 40 tree
species, while tropical Madagascar has more than 2000 (both countries have
similar forest areas of about 20 million ha).
· In all tropical broadleaved
forests only about 6.5% of the standing gross volume is actually
commercialized.
· In the majority of species good seed years are irregular
and infrequent.
· The growth of the volume actually commercialized (VAC) for
mixed forests is between 0.1-0.5 m3/ha/year.
· The gross annual allowable cut (AAC)
for intensively managed broadleaved forest is often estimated at between 0.5-1.0
m3/ha/year, but can reach or surpass 2 m3/ha/year.
· Logging intensities (America 8 m3/ha/entry; Africa 13 m3/ha/entry; Asia dipterocarp 40-100 m3/ha/entry but the overall average is 37 m3/ha/entry).
· Logging has become mechanized and
large machines are used, with inadequate supervision and control.
· The
damage to advance growth is the most serious since it affects an often very
limited number of individuals that, on release from crown competition, have
great growth potential and represent the next commercial crop from a given
area.
· Today it is a common occurrence to find 40-70% of the advance growth
destroyed in the harvesting process, leaving only between 12-33 stems/ha for the
next cut.
· Damage to advanced growth consists mainly of crown break, which
can be significantly reduced if lianas are cut some time in advance of felling,
and stem and butt bark scraping, the damage done to regeneration is mostly
caused by the passage of machines opening skid trails for log haul and preparing
landings.
· In 1958, 14% of the coupe area was bared by logging operations in
Insular Malaysia, while in 1965 the area bared was estimated to be 40%
(dipterocarps do not regenerate on bared soil and there are the added problems
of soil compaction, and disrupted water flow patterns.
· Very heavy damage
(70-100%) can be expected when basal area extracted rises above 12 m2/ha and there is poor control over logging
operations and careless handling of large machinery.
· General reduction in
damage through more careful control of operations and handling of the machinery,
pre-logging treatment of the stand (vine cutting), better overall planning of
the harvesting operations and by paying more attention to the training of
machine operators.
· The operational methods used in harvesting tropical
mixed forests have so far usually been designed to keep the cost of harvesting
as low as possible and so-called silvicultural systems were often developed as a
direct function of those methods.
· Although much has been written on
tropical silviculture, the fact remains that comparatively little is known of
the silvicultural requirements of many of the species in the tropical mixed
forest, and as to how this forest can be managed on a sustained yield
basis.
· Even in the more intensively logged dipterocarp forests, only 30% of
the total volume is actually commercialized.
Matelson, T.J., N.M. Nadkarni and R. Salano. 1995. Tree damage and annual mortality in a montane forest in Monteverde, Costa Rica. Biotropica 27(4): 441-447.
· 1403 live trees (742 10-30 cm dbh, 661 >30 cm dbh)
on a 4 ha research area tagged.
· Over 4 years 147 trees were severely
damaged over the four years.
· Mean number of damaged and dead trees was 15.9
trees/ha (9.9 in 10-0 cm dbh class and 6.0 in >30 cm dbh class) or 2.8% of
tagged trees per year.
· Of the 147 trees damaged, snapped or fallen, 116
were dead (i.e., did not sprout new growth).
· The mean annual mortality was
12.7 trees/ha (s=5.9) (8.2 for 10-30 cm dbh and 4.6 for >30 cm dbh).
·
Annual true mortality of 2.2% (2.1% for 10-30 cm DBH, 2.8% for >30 cm
DBH).
· Turnover time was calculated as the number of years necessary for all
of the originally inventoried trees to die [# of originally tagged trees/(# of
dead and snapped trees/time observed)] (Uhl 1982).
· For 10-30 cm DBH the
turnover time was 55.5 years, and for >30cm DBH it was 42.4 years.
· The
2.2% annual mortality rate is mid-range of annual mortality rates of other
tropical forests (1-3% as published in Putz & Milton 1982, Uhl 1982, Brown
et al. 1983, Lang & Knight 1983, Higuchi 1987, Manokaran & Kochummen
1987, Hartshorn 1990, Lieberman et al. 1990, Swaine et al. 1990 - of which most
are from lowland tropical regions).
Mattsson-Marn, H.G. 1982. The planning and design of the forest harvesting and log transport operation in the mixed dipterocarp forest of Sarawak. Food and Agriculture Organization of the United Nations, FO:MAL/76/008, Field Doc. No. 17. 76pp.
· Report describes the system of logging in use, as well
as the situation of forest engineering in Sarawak in 1978.
· Recommends the
use of large scale topographic maps for planning roads and skid trails, the
opening of the trails prior to felling, direction felling toward the skid
trails, and the use of chokers and logging arches for skidding.
· Recommends
strengthening the Forest Department for improved planning, construction and
control of road construction, as well as logging operations on a whole, and that
the long-term licensees also be fully responsible for planning the harvesting
operations and road networks, and that they employ a sufficient number of
adequately trained staff for such operations.
· In the mixed dipterocarp hill
forests the average tree size is 5-6 m3/stem and
60-80 cm dbh (generally varies from 45 to 140 cm dbh, with a maximum of 200 cm;
but most big trees are hollow); the minimum felling limit is 45 cm dbh;
potential net industrial volume (all species >46 cm dbh) 131.4 m3/ha, however, only 28.7 m3/ha is the actual yield (Field Doc. 4).
· With
better planning of roads and logging operations, access will improve, and damage
and wastage will be reduced.
· Report outlines the logging operations which
are basically unplanned and uncontrolled, resulting in considerable operational
inefficiencies and damage to residuals and the site, as well as damage to the
logs.
· A serious problem facing the logging industry in the mixed
dipterocarp forest in Sarawak is the almost complete lack of trained personnel
in all categories, a problem which hinders the development of sound and
economical operations.
· Report outlines the results from two case studies
already presented in other reports (e.g., Mattsson-Marn and Jonkers 1981,
Mattsson-Marn et al. 1981).
· The situation in 1981:
eight companies have sent personnel to the Logging Training School
two companies were making detailed planning maps, while four others were starting such activities
many licensees are changing from square cut block boundaries to boundaries which follow the natural terrain features
most companies were supplied with 1:25000 aerial photographs of their areas
one company started to use a highlead/skyline system, while four companies were using FMC steel tracked skidders, and two companies were using chokers and one company a logging arch on crawler tractors
Mattsson-Marn, H.G. and Jonkers, W. 1981. Logging damage in tropical high forest. Food and Agriculture Organization of the United Nations, Project FO:MAL/76/008, Working Paper No. 5. 15pp.
· Review of two studies carried out in the mixed
dipterocarp hill forest in Sarawak.
· First study compared current logging
practice (122 ha, logging intensity 53 m3/ha)
with planned RIL (122 ha, logging intensity 55 m3/ha) (with RIL overall damage to residuals reduced
by 50%, skidding efficiency increased by 36% (20 m3/h vs. 14.7 m3/h)
and there was no cost increase with directional felling).
· In the current
system trees are felled in the direction convenient to the feller and thus are
scattered at random over the block. Skid trails go from log to log, and thus are
long, steep and winding (sometimes completing a full circle) with sharp curves.
As a result the skidding tends to be slow and damages to logs and the residual
stand are excessive.
· Skidding costs in planned operation (including
planning, opening up trails, supervision and skidding) was M$4.56/m3 (M$0.24/m3+M$4.32/m3),
compared to M$5.94/m3 for the current
system.
· The cost of preparing the topographic map was M$0.23/m3, but most of this charge should be against road
building and not skidding.
· Tree gaps in planned 17.1% of area, while in
current operations 30.4%.
· Both systems had 10.4% of area with bare soil
(landings and skid trails).
· Planned operation 13.3 trees/ha uprooted and
13.8 trees/ha broken.
· Current operation 25.8 trees/ha uprooted and 22.5
trees/ha broken.
· Minor damage slightly more in the planned block.
·
Found that 11 m3/ha (20% of a total volume of
sound timber felled of 55 m3/ha) of logs that
had been felled and bucked could not be located by the skidding crew and were
thus abandoned vs. 5.5 m3/ha in the planned
block.
· Second study compared logging intensities of 10 m3/ha (2 trees/ha), 32 m3/ha (6.25 trees/ha) and 55 m3/ha (13.3 trees/ha).
· Area occupied by skid
trails and landings the same, while temporary opening space increased from 5% to
30% through the range of logging intensities.
· Under current logging
practices some 60 trees/ha (or 40% of growing stock left after logging) of
desirable species are destroyed in logging 55 m3/ha, compared to an estimated 20-30 trees/ha in
lightly logged areas (although in the study the lowest intensity had 10 trees/ha
destroyed).
· The need to improve the standard of planning and execution of
logging operations in the mixed dipterocarp hill forest is stressed, not only
from the viewpoint of reducing the loss of actual and potential raw material,
but in order to ensure the perpetuation of the forest as a viable entity.
·
Found in studies in MDF in Sarawak that if selectively logging forest is treated
immediately after logging so that sound stems of desirable species are released
from competition, the logging cycle can be reduced and the harvestable volume
for the next cut will not be less than the first cut.
· About 4.4% of the
area logged is covered by secondary (40 m2/ha)
and feeder roads (400 m2/ha).
· Need proper
control of operations by trained supervisors.
Mattsson-Marn, H., E. Vel, O. de Jongh and D.C.K Hui. 1981. Planning and cost studies in harvesting in the mixed dipterocarp forest of Sarawak: Part I. Based on maps derived from ground survey. Food and Agriculture Organization of the United Nations, FO: MAL/76/008, Field Document No. 7. 76pp.
· Study of logging operations in a mixed dipterocarp
forest in Sarawak, Malaysia.
· Planning entailed: 1) topographic survey and
preparation of large scale topographic maps (1:3000) with contour interval of 5
m; planning the road and skid trail network and logging blocks on these maps;
and 3) aligning the roads, trails and blocks on the ground.
· Also used
direction felling to fell trees towards prepared trails to facilitate skidding
and minimize damage to the remaining stand.
· In the planned area the crawler
tractor was equipped with two chokers on a mainline.
· The planned operation
with directional felling was compared to a conventional operation with no
planning, no directional felling and a crawler tractor not using chokers.
·
In the planned operation, skidding efficiency increased 36%, overall damage to
the forest was reduced by 33%, 50% less volume of felled sound timber was left
in the forest, and no trees were split during felling.
· This was achieved
with no increase in felling cost, but rather with a reduction in cost of
23%.
· The total cost for planning of main skid trails, opening up trails,
supervision and skidding was $4.56/m3 (Malaysian
dollars), compared to $5.94/m3 for traditional
skidding.|
· The skidder operator in the planned area was not as experienced
as the other, thus, it was estimated that production could have been increased
by 70% (versus 36%) if similar skilled operators had been used.
· If the
$0.23/m3 cost for making the topographic maps is
included the cost advantage is reduced to 19% in favour of planned
harvesting.
· Planning and opening of trails prior to felling is a basic
requirement for an efficient logging operation, as is the large scale
topographic map that made the planning possible.
· To be fully effective the
planned logging operation must be supervised constantly by trained supervisory
personnel (included in above costs).
· The area was covered by a regular road
pattern consisting of one secondary road and five almost parallel feed roads
nearly perpendicular to the secondary road (4 km of secondary road (6.25 m/ha),
7.0 km of feeder road (11 m/ha)), for a total road density of 17.25 m/ha.
·
Overall costs involved in topographic survey and planning of roads and skid
trails ($ are Malaysian currency units):
|
$ per ha |
$/m3 =54 m3/ha) | |
|
Cost of topographic survey including office work |
12.68 |
0.23 |
|
Cost of road planning |
6.59 |
0.12 |
|
Cost of planning of main skid trails |
3.22 |
0.06 |
|
Total cost of survey and planning of roads and main skid trails: |
22.49 |
0.41 |
· Assuming 4 m wide trails 5% of area covered by trails
in planned and 7% in unplanned.
· Logging damage was only calculated for
commercial species.
· Planned area had 17.1% of areas as temporary open space
vs. 30.4% in unplanned.
· 13 trees/ha uprooted and 14 trees/ha broken in
planned block vs. 26 trees/ha uprooted and 22 trees/ha broken in unplanned
control area.
· Minor damage was slightly higher in the planned block
(assuming 35% of trees with minor damage will die based on other research),
thus, an additional 12 trees/ha in the planned and 11 trees/ha in the unplanned
areas would be lost to mortality.
· The total number of trees lost are
planned 40 trees/ha vs. unplanned with 60 trees/ha (33% less mortality).
· In
the unplanned area 3.3 felled trees/ha were left in the forest (0.8 trees/ha
showed extensive rot, 1.3 trees/ha were hollow and split during the felling
operation, and the remaining 1.3 logs/ha contained 11.5 m3/ha of sound timber.
· In the planned area 1.25
felled trees/ha were not or only partly extracted (none were split, two logs
(0.8 logs/ha) were free of serious defects and could have contributed 5.5 m3/ha).
· Summary of costs ($=Malaysian $,
1981)
|
Unplanned logging, $/m3 |
Planned logging, $/m3 | |
|
Topographic survey 10% inventory Road planning Planning of main skid trails Road construction Felling Skidding Supervision of felling & skidding Loading Road Transport TOTAL DIRECT LABOUR & MACHINE |
0.14 0.12 2.662 2.31 5.94 0.90 5.07 17.14 |
+ 0.321 0.12 0.06 2.66 2.29 4.38 0.12 0.90 5.07 15.92 |
|
OTHER LABOUR COSTS |
4.00 |
4.00 |
|
OVERHEAD COSTS (40%) |
10.57 |
9.96 |
|
TOTAL COST |
31.71 |
29.88 |
1The cost for a
separate topographic survey is $0.23/m3 and
for a separate inventory $0.14, but when done at the same time it is estimated
to be $0.32/m3.
2The cost of constructing a road planned in the
traditional way, to the same standard as was done in the planned area will
actually be higher.
Mattsson-Marn, H. and Jonkers, W. 1982. Logging damage in tropical high forest. In: Srivastava, P.B.L. et al. (eds.). Tropical Forests -- Source of Energy Through Optimisation and Diversification. Proceedings of an international conference held 11-15 November 1980 at Penerbit Universiti Pertanian, Serdang, Selangor, Malaysia. p.27-38.
· Harvesting operations utilizing detailed planning cost
20-45% less than comparable operations with minimal planning.
· The study
also found that better planning had better organization and supervision, fewer
accidents, fewer merchantable trees left unfelled and few logs lost after
felling.
Mauricio, F.P. 1984. Study cites environmental changes in selectively-logged Surigao forests: Parts I and II. The Philippine Lumberman 30(6 & 7): 7-13; 8-10,28.
· Study of logging in dipterocarp forests in rough
terrain of Eastern Mindanao, Philippines.
· Uncontrolled removal of
utilizable timber at the 10 to 15 years after logging caused excessive
destruction to the residual stands.
· Highly mechanized operations with
Berger and Washington Iron Works tower yarders.
· Continued decrease in stand
density up to the third year due to mortality of damaged and exposed trees.
·
Only 49.9% of the original stand was undamaged and non-defective after logging
(based on stem numbers).
· 20.1% of original stand was naturally
defective.
· 21.5% of original stand had logging damage.
· Assuming the
difference of 8.5% was removed (original about 440 stems/ha).
McNabb, K.L., Miller, M.S., Lockaby, B.G., Stokes, B.J., Clawson, R.G., Stanturf, J.A. and Silva, J.N.M. 1997. Selection harvest in Amazonian rainforests: long-term impacts on soil properties. Forest Ecology and Management 93: 153-160.
· The study area is located in the Brazilian
Amazon.
· The soil is a clayey Ferrasol, which is usually well drained, water
permeable, and highly resistant to erosion.
· A single tree selection harvest
of all commercial timber >55cm dbh and a selection harvest of all commercial
species >45cm dbh were applied.
· An average of 16 trees/ha was harvested
which translates to a volume extraction of 75 m3/ha.
· The data from both logging intensities and
from primary and secondary skid trails were summarised for analysis.
· Ruts
and skid trails were still visible 16 years after harvest.
· 16 years after
harvesting, 99% of the area were classified as minimally disturbed and 1% as
skid trails.
· In general, concentrations of nitrogen [N], phosphor [P],
potassium [K], and carbon [C] decreased with increasing disturbance intensity
while those of calcium [Ca] and magnesium [Mg] increased.
· There were
significant changes in bulk density, Ca and Mg concentrations between the
controls and the minimally disturbed areas.
· Bulk density data indicated
that soils remained compacted in all disturbance classes after 16 years.
·
The tendency for Ca and Mg concentration to vary directly with disturbance
intensity could be explained by increased weathering, increased mineralisation
or decreased plant uptake rates.
· Restricted rooting due to increasing bulk
densities as disturbance increases could cause the decrease in organic N and
C.
· Residual soil compaction might also contribute to reduced mineralisation
of P and K through reduced aeration and water holding capacity.
Megahan, W.F. 1977. Reducing erosional impacts of roads. In: Guidelines for watershed management. Food and Agriculture Organization of the United Nations, Rome, Conservation Guide 1. p.227-261.
· Experience by FAO in developing countries has often
shown that roads are the major source of erosion.
· Effects vary considerably
depending on the geologic, climatic, landform, soil and vegetation properties of
the area or country in question and upon the care taken to reduce erosion in all
phases of the road development project.
Meijer, W. 1970. Regeneration of tropical lowland forests in Sabah, Malaysia, forty years after logging. Malaysian Forester 33(3): 204-229.
· Average logging intensity in Sabah 1000 ft3/acre (=69
m3/ha).
· Between 20-40% soil disturbance
with heavy logging equipment.
· Area logged used highlead yarding.
· 40
years after logging dipterocarp volumes: logged plot (72 trees, 15 species,
18,884 ft3 per acre) and unlogged plot (76
trees, 17 species, 34,273 ft3 per acre).
· 40
years after logging the average dipterocarp volume per hectare is half of that
of adjacent primary forest.
· For non-dipterocarp species (except iron wood):
logged (26 trees, 22 species, 5834 ft3 per
acre); unlogged (17 trees, 16 species, 7853 ft3
per hectare).
· A comparison of a heavily disturbed site near the spar tree
with less disturbed forest yielded the following information per acre: heavily
disturbed (7 dipterocarps 3-5 ft girth, 434 ft3
per acre); less disturbed (15 dipterocarps 3-11 ft girth, 3296 ft3 per acre).
· In the disturbed area the greatest
volume (1354 ft3/acre) is occupied by Anthocephalus.
· Average dipterocarp forest in Sabah
can produce between 18-30 ft3/acre/year of millable (6 ft plus) timber over a
period of 40 years (50-83 m3/ha).
· A
selective system of logging with marking trees for retention would be the best
safeguard for a sustained yield of high productive tropical forest soils under a
60-80 year rotation.
· Areas of intensive soil disturbance can be traced back
even 40-45 years.
· The normal species composition of mature forest has
returned in the areas without soil disturbance where scattered mother trees
(about 5/acre) were left.
· Species of trees left unlogged have not become
more frequent than those that were harvested.
· Dipterocarp trees in girth
classes 4-6 ft (20-30 cm dbh) and defective trees >6 ft girth (>30 cm dbh)
should be left undisturbed in order to safeguard natural regeneration.
·
Better to not open up the stand so that pioneer species invade the site and slow
dipterocarp growth.
Mendoza, G.A. and A. Setyarso. 1986. A transition matrix forest growth model for evaluating alternative harvesting schemes in Indonesia. Forest Ecology and Management 15(3): 219-228.
· Transition matrix model constructed for tropical
forests in Indonesia, managed under the Indonesian Selective Logging System
(TPI) (east Kalimantan).
· TPI can support the second harvest, but shows that
the system's 35-year harvest cycle is too rapid to sustain the current yield
after it (e.g., when maintaining same harvest intensity and a 50 cm dbh diameter
limit).
· Adjustments must be made to the second and succeeding cuts in order
to proved sufficient growing stock for future harvests.
· TPI requires 25
residual trees/ha with a 35 year cutting cycle and 50 cm dbh cutting limit,
while the model indicates that 50 residual trees/ha are required.
· The
optimal TPI harvest intensity for the case study company forest was 67.3 m3/ha, while the company actually harvested 85.8 m3/ha.
· When the cutting cycle was reduced to 25
years, while retaining a 50 cm dbh cutting limit, the optimal harvesting
intensity was reduced to 51.9 m3/ha.
· When
harvesting 60% of trees in dbh class 40-60 cm, 80% in 60-70 cm dbh class and
100% of trees >70 cm dbh on a 35 year cycle, the optimum logging intensity
was 71.9 m3/ha.
Miller, T.B. 1981. Growth and yields of logged-over mixed dipterocarp forest in North Borneo. Malaysian Forester 44(2-3): 235-245.
· Net growth rate per hectare per year as a function of logging severity for eight plots in logged over forest (logging severity = % of original stems cut, damaged and destroyed per plot):
|
Logging severity, % |
Number of years since logging |
Net growth rate, m3/ha/year |
|
4 |
7 |
3.9 |
|
9 |
7 |
5.9 |
|
10 |
7 |
3.4 |
|
15 |
7 |
4,9 |
|
20 |
7 |
0.8 |
|
23 |
7 |
-1.7 |
|
36 |
2 |
-2.4 |
|
76 |
2 |
-16.3 |
· Mean diameter growth rates of undamaged trees 6 years after logging and similar trees in a virgin stand:
|
Dbh class, cm |
Mean diameter growth, cm/year | |||
|
Virgin Forest |
Logging severity | |||
|
4% |
15% |
20% | ||
|
15-24.9 |
0.2 |
0.4 |
0.4 |
1.6 |
|
25-34.9 |
0.6 |
0.4 |
0.6 |
1.2 |
|
35-44.9 |
0.7 |
0.4 |
1.0 |
1.6 |
· Differences in net growth rates for the plots indicate
that cutting cycles will vary considerably over the concession; some areas will
have replaced the volume removed in less than 5 years, in other areas regrowth
will take considerably longer than 40 years.
· This preliminary analysis
suggests that 2-3 m3/ha/year net growth rate
after logging is achievable (compared to their plantation growth rates of 12-20
m3/ha/year).
Mohd Shahwahid, H.O., Awang Noor, A.G., Abdul Rahim, N., Zulkifly, Y. and Tazuni, U. 1999. Trade-offs among competing uses of Malaysian forested catchments. Environment and Development Economics 4: 279-311.
· Costs and benefits of three land use options (catchment protection [CP], conventional logging [CL] and reduced impact logging [RIL]) were evaluated for catchments in Selangor, Malaysia.
· A water regulatory dam and three regulatory dams are
located within the study area.
· Harvesting intervals range from 30-35 years,
with cutting limits no lower than 50cm dbh for dipterocarp and 45cm dbh for
non-dipterocarp timber species.
· For both the RIL and the CL option the net
timber yield is 49.3 m3/ha for the first cutting
cycle and 31.6 m3/ha for the second cutting
cycle.
· Residual stocking minimum is 32 trees/ha of commercial species of
good quality from diameter class 30-45cm or its equivalent.
· For RIL a 20m
wide buffer was designated along streams, for CL the buffer was reduced to 5m
width.
· Studies by Rahim (1998) and Baharuddin (1988 and 1995) have
revealed that the rate of sedimentation tends to recover five years after
logging operations provided that no further encroachment occurs in the logged
area.
· RIL can significantly reduce the amount of sedimentation by imposing
further control measures such as better road planning, and monitoring and
enforcement of forest management specifications. Therefore a yield reduction
factor of 0.6 was assumed for RIL operations when compared to conventional
harvesting practices.
· Costs and revenues of timber production (US$ 1 = RM 3.80 [1998]):
|
Catchment Protection |
Reduced Impact Logging [US$] |
Conventional Logging [US$] | |
|
Revenue |
- |
4,195,731 |
4,918,140 |
|
Direct logging cost |
- |
1,676,286 (83.4%) |
1,964,905 (83.7%) |
|
Rehabilitation cost |
- |
71,620(3.6%) |
122,867 (5.2%) |
|
Administration and management cost |
- |
261,307 (13.0%) |
261,307 (13.0%) |
|
Total cost |
- |
2,009,213 (100%) |
2,349,080 (100%) |
|
Net present value |
- |
2,186,517 |
2,569,060 |
· The higher logging and rehabilitation cost of timber
production under the CL option significantly reduces its net present value
compared to RIL operations.
· Costs and revenues of treated water
production:
|
Catchment |
Reduced Impact Logging [US$] |
Conventional Logging [US$] | |
|
Revenue |
7,651,629 |
7,651,629 |
7,651,629 |
|
Direct production cost |
2,652,246 (82%) |
2,652,246 (82%) |
2,652,246 (82%) |
|
Treatment cost |
582,326 (18.0%) |
1,897,616 (41.7%) |
2,760,688(51%) |
|
Total cost |
3,234,573 (100%) |
4,549,831 (100%) |
5,412,934 (100%) |
|
Net present value |
4,417,056 |
3,101,767 |
2,238,695 |
· Costs and benefits of hydro-electric power production:
|
Catchment Protection |
Reduced Impact Logging [US$] |
Conventional Logging [US$] | |
|
Revenue |
5,914,259 |
5,914,259 |
5,914,259 |
|
Production cost |
4,480,499 (98.3%) |
4,480,499 (98.3%) |
4,480,499 (98.3%) |
|
Production losses |
70,339 (1.5%) |
430,467 (8.7%) |
754,165 (14.2%) |
|
Maintenance cost |
8,551 (0.2%) |
198,828 (1.0%) |
91,716 (1.7%) |
|
Total cost |
4,559,389 (100%) |
52,323 (100%) |
5,326,380 (100%) |
|
Net present value |
1,354,870 |
950,969 |
587,879 |
· Net present value of the three land use options:
|
Catchment Protection [US$] |
Reduced Impact Logging [US$] |
Conventional Logging [US$] |
Incremental Net Present Value |
Incremental Net Present Value (CL->CP) [US$] | |
|
Sub-total timber |
- |
2,186,517 |
2,569,059 |
+2,186,517 |
+2,569,059 |
|
Treated water |
4,417,056 |
3,101,767 |
2,238,695 |
-1,315,288 (-29.8%) |
-2,178,361 (-49.1%) |
|
Hydroelectric Power |
1,354,870 |
950,969 |
587,879 |
-403,900 (-29.8%) |
-766,990 (-56.6-5) |
|
Sub-total water |
5,771,926 |
4,052,736 |
2,826,574 |
-1,719,189 (-29.8%) |
-2,945,351 (-51.0%) |
|
Net present value |
5,771,926 |
6,239,254 |
5,395,634 |
+467,328 (+8.1%) |
-376,292 (-6.5%) |
· The efficient choice among the two logging methods is
the RIL option owing to the higher returns and the lower externality imposed
upon the status quo water users.
· The returns from timber cannot meet that
from the status quo production of treated water under both logging methods.
However, complementing water uses with logging in forested catchments is
efficient where hydroelectric power is produced.
· These findings cannot be
extended to other forest catchments without making adjustments to the numerical
results, such as incorporating different rates of sedimentation, rainfall
and
sediment concentration.
· Future studies should consider using shadow prices
instead of negotiated prices for treated water and hydro-electric power by
estimating the marginal costs of production in a new hydro-electric power plant
or water treatment plant or of alternative power plants and production of
treated water from alternative sources such as groundwater.
Mok, S.T. 1992. Potential for sustainable tropical
forest management in Malaysia. Unasylva 43(169): 28-33.
· The MUS has
been substantially modified over time with a shift toward more selective felling
and the retention of advance growth as well as a more discriminating use of
poison girdling as a silvicultural tool.
· Integrated studies in forest
management operations in Peninsular Malaysia show that with average annual
growth rates of 0.8 to 1.0 cm in diameter and 2 to 2.5 m3/ha in gross commercial volume for trees of more
than 30 cm dbh, about three-quarters of the hill forest is capable of producing
at least 40 to 45 m3/ha every 30 years - this is
about the current average outturn of the virgin hill forests.
· Growth and
yield studies in Sabah and Sarawak have shown similarly positive results.
Mori, S. 1992. An example of sustainable forest management in West New Britain Island of Papua New Guinea. In: Beyond the guidelines - an action program for sustainable management of tropical forests. International Tropical Timber Organization, Technical Series No. 7. P.157.
|
Species |
Cutting cycle years |
Size of tree |
Standing volume m3 |
Harvest volume m3 |
Uses | ||
|
Height, m |
DBH, cm |
Sawn/ply |
Pulp | ||||
|
Eucalyptus deglupta |
20 |
50-60 |
70-75 |
400-500 |
300-400 |
OK |
OK |
|
Octomeles sumatrana (Ertma) |
15 |
40-50 |
80-85 |
400-500 |
300-400 |
OK |
Not suitable |
|
Terminalia b. |
20 |
50 |
70-75 |
400-500 |
300-400 |
OK |
Not suitable |
|
Tectona grandis |
25 |
40 |
65-70 |
400 |
300 |
OK |
OK |
Moura-Costa, P. 1997. Reduced impact logging techniques as a means for carbon offsets. In: Proceedings of the FAO/IUFRO Satellite Meeting held in conjunction with the IUFRO XX World Congress, Tampere, Finland, 4-5 August, 1995, Research on Environmentally Sound Forest Practices to Sustain Tropical Forests. Food and Agriculture Organization of the United Nations. P.37-45.
· RIL experiment in Sabah, Malaysia.
· 8-15 trees/ha
(80 m3/ha) normally extracted in logging in E.
Malaysia, which can result in up to 50% of the residual stand damaged and up to
40% of the area crushed by bulldozers.
· Uncontrolled logging has a severe
impact on biodiversity and ecosystem function, and leads to increased soil
erosion, weed infestations and incidence of fire.
· These effects combine
with the destruction of much of the pre-existing regeneration of commercially
valuable trees to make uncontrolled logging extremely detrimental to long-term
ecological and economic productivity.
· Training needed at all levels of the
hierarchy - from tree fellers to senior management.
· In conventional logging
bulldozer traversed area can be up to 30-40% of the area.
· RIL reduced the
area of log landings by 50%.
· Figures of logging impacts after harvesting of
120 m3/ha in hilly area in Sabah following RIL
(reduced impact) and CNV (conventional) logging from ca. 800 ha:
|
Reduced impact logging |
Conventional logging | |
|
Roads |
20 m/ha 1.6% of logged area |
24 m/ha 3.3% of logged area |
|
Skid trails |
71 m/ha 4% of logged area |
205 m/ha 13% of logged area |
|
Log landings |
57 m2/ha |
103 m2/ha |
|
Residual trees damaged |
29% |
56% |
· In the initial analysis the operational costs of RIL
are higher than those of conventional logging due to the extra activities
required (detailed inventories, training, climber cutting, intensive
supervision).
· However, after the initial phase of learning and intensive
training it is expected that RIL operations will run more smoothly and
efficiently than in conventional logging.
· This may lead to savings through
reduced use of bulldozers, with lower fuel and maintenance costs.
· Added
benefit of a sense of pride in the logging crews and field staff.
· Training
of the logging crews has triggered a positive catalytic effect on the logging
attitude around the region (professional pride and competition has led to an
unexpected improvement of the performance of other logging crews operating in
the ICSB's concession).
Muladi, S. 1996. Quantification and use of dipterocarp wood residue in east Kalimantan. In: A. Schulte and D. Schöne (eds.). Dipterocarp Forest Ecosystems: Towards Sustainable Management. World Scientific Publishing Co. Pte. Ltd., Singapore. p.603-615.
· Since 1981, when the Indonesian government blocked
roundwood exports, followed by a total ban in 1985, 2708 sawmills and 117
plywood mills have been built.
· The large and medium size mills are
concentrated in Kalimantan (59.3%), with about 23% located in east
Kalimantan.
· Logs produced accounted for 63.2% of the felled trees, with
residue being 36.8% (stump 5.3%, buttress 3.8%, defective logs 6.0%, branches
21.7%).
· Logging intensity was 5.2-6.9 trees/ha (42-67 m3/ha) extracted for four logging sites totaling 130
ha.
· Sawmill recovery rate was 50% and residue 35% by volume for logs
received at the mills.
· Plywood conversion efficiency was 42-65%, with an
average rate of 55%.
Muñoz, R.R. Costo de la regencia para el aprovechamiento forestal. Colegio de Ingeniores Agrónomos de Costa Rica. 1997.
· This study was carried out in Costa Rica, where the
commercial timber value ranges from 90 to 1712m3/ha.
· Average labour costs are US$ 2.39/m3.
· Average costs for forest utilisation in Costa
Rica:
|
US$/m3 |
% | |
|
Value (per m3 of wood) |
37.80 |
47.02 |
|
Management Plan |
2.99 |
3.72 |
|
Regency |
0.58 |
0.72 |
|
Utilization |
21.16 |
26.32 |
|
Sub-Total |
62.53 |
77.78 |
|
Profit (30%) |
17.86 |
22.22 |
|
Total |
80.39 |
100.00 |
· Distribution of the management costs:
|
US$/m3 |
% | |
|
Honorarium |
69.11 |
53.33 |
|
Transportation |
22.67 |
17.49 |
|
Travel allowances |
15.12 |
11.67 |
|
Office |
7.56 |
5.83 |
|
Procedures |
15.12 |
11.67 |
|
Total |
129.58 |
100.00 |
Mussong, M., Singh, K., Laqeretabua, J. and de Vletter, J. 1996. Ökonomische Auswirkungen unterschiedlicher Nutzungsintensitäten in tropischen Regenwäldern Fidschis. Forstarchiv 67: 82-87.
· Criteria for conventional exploitation and modified logging intensities:
|
Criteria |
Conventional logging [CL] |
Reduced Impact Logging (Harvesting Intensity) | ||
|
High [HL] |
Medium [ML] |
Low [LL] | ||
|
Number of target diameter classes |
1 |
3 |
4 |
5 |
|
Minimum target diameter |
35 |
35-60-100 |
35-50-75-105 |
40-50-65-80-110 |
|
Harvesting intensity |
_80 |
50-60 |
30-40 |
15-20 |
· Reference values for the various logging intensities:
|
CL |
HL |
ML |
LL | |
|
Performance (timber harvesting) |
||||
|
Roads (m/m3) |
0.30 |
0.20 |
0.39 |
0.94 |
|
Skid trails (m/m3) |
3.35 |
2.38 |
5.13 |
8.86 |
|
Felling (m3/day) |
20.48 |
23.92 |
25.97 |
16.95 |
|
Skidding (m3/day) |
18.00 |
19.28 |
20.97 |
22.32 |
|
Bucking (m3/day) |
64.71 |
89.00 |
117.48 |
88.93 |
|
Loading (m3/day) |
24.24 |
33.41 |
43.84 |
33.91 |
|
Transport (m3/day) |
5.14 |
5.14 |
5.14 |
5.14 |
|
Planning and supervision (h/ha) |
5.5 |
10.2 |
9.4 |
8.8 |
|
Layout of harvesting units (h/ha) |
- |
3.0 |
3.0 |
3.0 |
|
Inventory (h/ha) |
- |
13.0 |
13.0 |
13.0 |
|
Selection of trees for harvest (h/ha) |
- |
13.3 |
11.4 |
10.0 |
|
Data from the study sites: |
||||
|
Area harvested (ha) |
42.3 |
35.5 |
56.6 |
41.8 |
|
Stand volume (m3_ 35cm dbh) |
3084 |
5811 |
7306 |
5000 |
|
Harvesting intensity (m3) |
2517 |
3309 |
2824 |
858 |
|
Volume sold (m3) |
1741 |
2198 |
1797 |
542 |
|
Average stem volume (m3) |
1.51 |
1.94 |
3.18 |
3.84 |
|
Harvesting (US$/m3) |
27.99 |
24.83 |
24.33 |
28.06 |
|
Fees and Taxed (US$/m3) |
10.65 |
11.44 |
11.28 |
9.84 |
|
Management (US$/m3) |
0.20 |
1.15 |
1.67 |
3.08 |
|
Sum |
38.84 |
37.47 |
37.29 |
40.98 |
· Assumed felling cycles:
|
Treatment |
Cutting cycle (years) | ||
|
Optimistic |
Realistic |
Pessimistic | |
|
CL |
35 |
45 |
55 |
|
HL |
20 |
30 |
40 |
|
ML |
10 |
15 |
20 |
|
LL |
6 |
10 |
15 |
· Profit calculation for the various management options:
|
Treatment |
Expenses (US$/m3) |
Income (US$/m3) |
Revenue (US$/m3) |
|
CL |
39.64 |
36.13 |
-2.51 |
|
HL |
36.27 |
36.18 |
-0.10 |
|
ML |
35.62 |
36.35 |
+0.73 |
|
LL |
37.90 |
36.75 |
-1.15 |
· The most favourable management concepts are HL and ML.
These options also ensure that non-timber forest products can be produced on a
sustainable basis.
· In order to minimise risk, the ML option seems to be
most favourable, because it minimises the impact on the residual stand without
compromising economic aspects.
Myers, N. 1983. Tropical moist forests: over-exploited
and under-utilized? Forest Ecology and Management 6(1): 59-79.
· The
great bulk of tropical moist forests are located in a belt that receives almost
half the planet's rainfall on land, but only occupy about 7% of the land
surface.
· The impact of tropical downpours causes substantially more soil
erosion than anywhere else in the world; e.g., eroded areas in Indonesia exceed
one-fifth the national territory.
· Current harvest patterns correspond , in
their haphazard form, to hunter-gather types of agriculture - thereby offering
much scope for rational and systematized expansion.
· Since we know less
about the workings of TMF ecosystems than we do about any other biome on earth,
we need to adopt a cautious approach to our use of them.
Neil, P.E. 1984. Climber problems in Solomon Islands forestry. Commonwealth Forestry Review 63(1): 27-34.
· As the intensity of logging increases, the decrease in
shading allows climber species to become the dominant vegetation.
· During
the 1960's and early 1970's logging was more selective and soil damage by
extraction affected 10-15% of the area and the canopy was broken in places but
by no means removed.
· In the late 1970's, with the increase in number of
species utilized and acceptance of small logs, logging became increasingly
intensive and became essentially a clearfelling with up to 70% of the area
disturbed or compacted.
· The result was a massive invasion of climbers that
choke out the natural regeneration and planted trees.
· In one example, nine
maintenance operations were required annually to control the climbers and the
cost of these operations was considerable.
· In larger gaps climber
infestations can remain the dominant vegetation log after logging operations
have ceased.
Nguyen-The, N., Favrichon, V., Sist, P., Houde, L., Bertault, J.G. and Fauvet, N. 1998. Growth and mortality patterns before and after logging. In: Silvicultural research in a lowland mixed dipterocarp forest of East Kalimantan. Cirad-foret. 1998.
· In primary forest, the overall annual mortality rate
was 1.5% in number of stems (9 stems/ha*year; 0.57 m2/ha*year).
· The mortality was calculated based
on three harvesting intensities (low impact logging with remaining basal area
_80%, intermediate with remaining basal area between 70 and 80% and high impact
logging with remaining basal area _80%).
· The mortality after logging was
2.5% per year, no differences could be detected between the three logging
treatments over a period of 2 years.
· The drastic reduction of damages
obtained with RIL methods during the harvesting process did not result in a
significant reduction of the subsequent mortality.
· The injured trees
composed 26% of the residual stand and they constituted 51% of the trees that
died during the following 2 years.
Nicholson, D.I. 1958a. Natural regeneration of logged tropical rain forest, North Borneo. Malaysian Forester 21(2): 65- 71.
· Soil disturbance by tractor trails bare of regeneration averages 14% of area.
Nicholson, D.I. 1958b. An analysis of logging damage in tropical rain forest, North Borneo. Malaysian Forester 21(4): 235-245.
· 53% of residual trees were damaged.
· Fallen and
broken off trees 30%, bark damage 11%, crown damage 4%, for total damage
45%.
· Trees with little damage 8%, undamaged trees of good form 35%,
undamaged trees with poor form 12%, for 55% little or not damaged.
· The
volume extracted was 4.7 trees/acre (1308 hoppus ft3/acre) = 116.5 m3/ha @ 11.6 trees/ha removed.
· The amount of
damage to residuals increases with logging intensity.
· Shown that even with
an average of 45% of the stand damaged, there remain about 20 trees/ha between
10-60 cm dbh which have suffered no damage and which could yield a stand as good
or better than the one just logged.
· However, the above analysis does not
take into account trees felled during roading or felling.
Nicholson, D.I. 1965. A review of natural regeneration in the Dipterocarp Forests of Sabah. Malaysian Forester 28(1): 4-26.
· To get dipterocarp regeneration need a sufficient
number of seedlings in the area after logging.
· One should always find a
large number of dipterocarp seedlings on the ground before logging, although
there are exceptions.
· There is a general tendency for the intensity of
logging to increase with the passage of time and for tractor damage to
increase.
· The 14% of bared area in typical logging areas given by Nicholson
(1958) is now very often exceeded and figures as high as 40% have been
estimated.
· Though some rise is probably inevitable, it is not conceded that
tractor damage must rise in proportion to the intensity of logging.
· Growth
response of undamaged trees after logging (rate still increasing in logged
areas):
|
Size class, feet (dbh) | ||||||
|
1 |
2 |
3 |
4 |
5 |
Mean | |
|
CAI before logging, in. |
0.35 |
0.57 |
0.60 |
0.66 |
0.64 |
0.50 |
|
CAI 1-year after logging, in. |
1.08 |
1.56 |
1.80 |
0.87 |
1.49 |
1.36 |
|
Number of trees/acre |
2.4 |
1.5 |
1.0 |
0.7 |
0.9 |
6.4 |
· It cannot be too strongly stressed that a
well-regenerated forest depends on a careful logging operation.
· Only
extraction has the potential to reduce the regenerating forest to a mass of
useless weeds, by destroying existing seedlings and poles.
· The most
destructive damage appears to stem from inefficient use of tractor tracks,
widening of tractor tracks to avoid boggy areas, and large collection points
near loading points (landings).
· Much damage to poles could be avoided by
considerate use of the dozer blade and by ensuring that the logs on haul do not
debark or shatter the roots of young commercial trees.
· The use of the
tractor winch and cable would lessen tractor-logging damage.
Nicholson, D.I. 1979. The effects of logging and
treatment on the mixed dipterocarp forests of Southeast Asia. Food and
Agriculture Organization of the United Nations, Rome, Rep. FO:MISC/79/8.
65pp.
· Increasing impact of logging, probably due to a reduction in
quality of supervision and training following the end of the colonial period,
increased use of mechanized equipment (as opposed to manual methods or animal
skidding), careless handling of machinery by unskilled operators, and increasing
reliance on horsepower rather than on technical competence.
· Costs are not
dealt with critically, but avoidance of logging damage is seen as a very
necessary and satisfactory way of increasing yield under present
conditions.
· Limiting tractor or cable damage and marking for felling and
retention are seen as practical ways of doing this.
· Selective logging is
seen as a workable system, given better control of logging.
· Need for prior
inventory data is stressed (deal with problems areas and provide a basis for
residual marking).
· In the late 70s the literature on the situation in the
late 50s and 60s was still applicable; logging intensities were still very much
the same, though very variable.
· Most of the growth data from yield plots
indicate very rapid seedling and sapling increment, e.g. 1.9 cm/year in diameter
growth in 4-year-old regeneration (dipterocarp need direct sun for rapid
growth).
· Important to retain sufficient advance growth after logging to
ensure sustainability.
· In the Philippines it is of interest that the
felling limits set in 1973 approximate very closely to a simple 70 cm limit, for
average diameter distribution. It is agreed that some cutting in the 55-65 cm
size could be beneficial but unless closely watched, abuses such as taking the
best 25% rather than the worst, could occur.
· Dipterocarps need a heavy
logging and then a long period of closure as can be provided by a bi-cyclic
system. However, it may be necessary to impose limits on the first cut in the
interest of those that follow.
· In the late 1950s about 14% of the area was
bared by tractors, while in the 1970s >40% was being bared.
· Dipterocarps
do not regenerate well on bared soil and it may be 10-15 years before tractor
tracks become similar to undisturbed areas.
· It cannot be too strongly
stressed that a well regenerated forest depends on a careful logging
operation.
· Much higher commercial MAI with longer logging cycles (e.g. in
Philippine untreated stand case studies, a 30 year cycle 1.6-2.8 m3/ha/year, while a 40 year cycle 2.0-3.5 m3/ha/year).
· It is reasonable to use a minimum
figure of 1 cm/year diameter growth for all sizes and the error if any, would be
on the safe side; for silviculturally treated stands a minimum value of 1.25
cm/year can be used.
· It seems quite clear that even with the low degree of
control being exercised over logging, that a significant volume can be obtained
after 30 years from felling. Any improvement in logging practice that preserves
more of the advance growth must have a marked effect on this intermediate
yield.
· The treated volume at 40 years is about 80 m3/ha (@ 1.25 cm/year diameter growth).
· Andel
(1978) shows from one example that proper logging control in West Malaysia may
add M$51-70/ha, whereas a post logging silvicultural treatment (including
planting of roads and landings) may cost about M$200/ha.
· Even if more
nearly equal, the repair of a bad logging operation by post-logging treatments
must be more expensive when one considers the only available replacement for a
destroyed tree, is a seedling which will take so much longer to produce saleable
wood.
· Therefore, though it can be shown that advance growth is greatly
benefited by freeing from competing trees, the preservation of the tree in the
first place is of more vital importance.
· Too short a cutting cycle will
have very serious effects on yield, if not on permanence of the dipterocarps
themselves. Even the 40 year cycle suggested here may have to be lengthened if
significant seeding does not occur by this time. Certainly very short pulpwood
rotations in conjunction with enrichment with fast growing species cannot be
considered in dipterocarp management since no seeding at all will occur.
·
Area destroyed by tractors needs to be limited to a maximum of 20-25%.
·
Selective logging is recommended wherever there is sufficient advance
regeneration present, otherwise some sort of MUS with planting is required.
·
Philippines - the logging cycle should be about 40 years.
· Sabah - due to
excessive logging and stand damage in the past a 60 year cycle will be needed to
get the stands back into better shape, after which a 40 year cycle could be
used.
· Sarawak - 40 year cycle is recommended, but believes the current 45
cm diameter cutting limit is too low.
· West Malaysia - due to problems with
inventory and logging, a 60 year cycle is recommended. Again like in Sabah, it
should be possible to go to a 40 year cycle once the forest becomes stable.
·
Indonesia - 40 year cycle with a minimum yield of 2 m3/ha/year is possible when silviculturally
treated.
Niedermaier, P. 1984. Plywood substitutes urged for maximum forest utilization: Parts I and II. The Philippine Lumberman 30(7 & 8): 11-16; 8-13,30.
· Product yields on roundwood that can generally be expected:
sawnwood 56-68%
plywood 50%
waferboard 75-80%
strandboard 85-90%
particle board 90-95%
thin particle board 100%
high density fiber board 95%
medium density fiber board 85-90%
· Plywood substitutes will result in better forest utilization.
Nik, A.R. and D. Harding. 1993. Effects of selective logging methods on water yield and streamflow parameters in Peninsular Malaysia. Journal of Tropical Forest Science 5(2): 130-154.
· Mean basal area in the watershed studied was 26.9
m2/ha (held as a well stocked forest).
·
Study of the effect of commercial (conventional) logging and planned/supervised
logging on water flow in streams after logging.
· Commercial logging had a
minimum cutting dbh for dipterocarps of 60 cm and 45 cm for non-dipterocarps,
minimal road planning, 60 m/ha of logging road and 80 m/ha of skid trail, and no
buffer strips specified.
· Planned/supervised logging had a minimum cutting
dbh for dipterocarps of 90 cm and 60 cm for non-dipterocarps, good road planning
with minimum coverage (<6%), grades (<20%), culverts and cross drains, 70
m/ha of logging road and 30 m/ha of skid trail, and 20 m buffer strips on each
side of the stream.
· The stocking removed (assuming percent of basal area)
in the commercial logging was 40% while in the supervised logging it was
33%.
· The commercial logged area resulted in 55% higher water yield than the
supervised logged area, although the percent of forest removal was only 21%
higher (i.e., 40% vs. 33%).
· Skid trail density was 60% higher in the
commercial logged area, and the ground disturbance (skid trails, logging roads,
landings) was limited to 5.1% in the supervised area as compared to 7.1% in the
commercial area.
· Study demonstrated the positive effects of
planned/supervised logging on hydrological responses.
Nikles, D.G. 1992. Successful domestication and conservation of an indigenous rainforest conifer (Araucaria cunninghamii) by means of plantations. In: Beyond the guidelines - an action program for sustainable management of tropical forests. International Tropical Timber Organization, Technical Series No. 7. P.163.
· Grows in PNG and NSW (Australia) to heights of >60
m and dbh >190 cm.
· 45,000 ha of plantations since 1920's.
· Rotation
of 50 years or earlier (best trees at this time 40 m tall and 80 cm dbh with a
merchantable volume of 8 m3).
· MAI averages
12-18 m3/ha/yr.
Noack, D. 1995. Making better use of tropical timber resources. ITTO, Tropical Forest Update 5(2): 12-13.
· After three years of study ranging across four
tropical countries (Ghana, Cameroon, Indonesia (East Kalimantan) and Malaysia
(Sarawak), it is possible to report that greater efficiency in forest and
processing operations could greatly enhance the sustainability of the tropical
timber industry.
· Report on ITTO project PD 74/90 (available from ITTO
Secretariat).
· Of total tree on average 4.6% in stump, 5.2% in buttress,
53.5% extracted log, 10.4% stem offcuts, 26.3% crown diameter >20 cm.
· Of
stem between crown and stump 77.4% extracted as log.
· Sawmilling yield (four
countries compared):
|
Yield of sawn timber, % |
Yield of wood residues, % | |||||
|
Main product |
Total |
By-product |
Solid residues |
Total |
Sawdust | |
|
Ghana (2 mills) |
44 |
49 |
5 |
40-43 |
51 |
8-10 |
|
Cameroon (3 mills) |
36 |
64 |
||||
|
Indonesia (2 mills) |
50 |
36 |
50 |
14 | ||
|
Malaysia - swamp logs (local market) - dipterocarp (export market) |
45 57 |
47 |
55 43 |
8 | ||
· There is a great influence of log quality on sawmill
yield.
· Timber yield could be increased if mills used log rotation equipment
at the first saw, which would enable the sawyer to cut each log optimally with
regard to cracks and other defects.
· Also important is accuracy of sawing in
order to avoid variations in board thickness that often exceeded 10 mm.
·
Relatively small amounts of solid residues were used locally for joinery,
furniture or charcoal production or as firewood.
· The situation was even
worse for sawdust.
· Enormous potential for efficiency gains possible in
logging and in mill processing.
· A thorough pre-logging inventory is an
important step in efficient logging.
· Logging techniques need to be improved
to reduce logging damage (needs regulations and encouragement for
concessionaires, training of logging personnel and research into the most
appropriate machinery).
· Need proper road planning.
· Government policy
should aim to encourage the use of forest residues without compromising the
sustainability of forest management.
· Different wood processing lines should
be integrated to the largest extent possible (e.g., raw material sorting in a
central log yard according to different wood processing lines (sawmilling,
plywood, moulding products) may increase overall yield).
· Development of
downstream products from wood residues.
· Urgent need to increase the level
of technology (e.g., higher accuracy sawing, reduced saw kerf, log rotating
equipment).
· In addition to modernization, need to raise the skill of the
workers by practical training and education (i.e., machine operators at headrig,
edgers and trimmers).
· Need establishment of quality control in the
mills.
· Downstream activities such as furniture manufacturing, parquet
flooring and profile board production should be encouraged.
· Conversion of
wood into energy, especially to provide power for the wood processing industry
itself, should be developed.
Nussbaum, R. and A.L. Hoe. 1996. Rehabilitation of degraded sites in logged-over forest using dipterocarps. In: A. Schulte and D. Schöne (eds.). Dipterocarp Forest Ecosystems: Towards Sustainable Management. World Scientific Publishing Co. Pte. Ltd., Singapore. p.446-463.
· The number of trees harvested per hectare in
dipterocarp forests varies but rarely exceeds 10-12 trees/ha.
· In Sabah the
cost of rehabilitating 7 ha of log landings with mixed indigenous species with a
2 x 1 m spacing was 1100 USD/ha (includes cost of planting stock, transport,
site preparation, planting and fertilizing).
Nwoboshi, L.C. 1987. Regeneration success of natural management, enrichment planting, and plantations of native species in West Africa. In: Mergen, F. and J.R. Vincent (eds.). Natural Management of Tropical Moist Forests - Silvicultural and Management Prospects of Sustained Utilization. Yale University, School of Forestry and Environmental Studies, New Haven, Connecticut. p.71-91.
· The limited forest land base in West Africa.
·
Enormous pressure for its conversion to other uses.
· Failure of natural
regeneration systems and continuously increasing demand for wood make the
plantation system the most logical choice for the region.
Ola-Adams, B.A. 1987. Effects of logging on the residual stands of a lowland rainforest at Omo Forest Reserve, Nigeria. Malaysian Forester 50: 403-413.
· Study based on a single 1 ha plot subjectively located
in a 5 month old logged compartment.
· Manual logging where logs lifted
directly onto lorries which gained access along hand-cut access routes.
·
Basal area in undisturbed forest generally 29 m2/ha; disturbed forest 14.3 m2/ha; and secondary regrowth 11.7 m2/ha.
· Logging intensity was 9 m3/ha.
· In the 1 ha plot there were 3 stumps, 670
trees (girth bh >10 cm) left.
· 17.7% of the residual trees were
damaged.
· 51 trees were knocked over (mostly in the >30 cm girth
class).
· 8% of area bared, compared to 30% for mechanized operations.
Ong, R.C., P.M. Logan, R. Glauner, M. Kleine and K. Uebelhör. 1996. Examples of sustainability criteria for dipterocarp forest management. In: A. Schulte and D. Schöne (eds.). Dipterocarp Forest Ecosystems: Towards Sustainable Management. World Scientific Publishing Co. Pte. Ltd., Singapore. p.274-292.
· It was found that numerous indicators and their
corresponding specifications already exist, however, may are difficult to
assess.
· Also it is impractical to scrutinize a large number of
specifications each time an evaluation or inspection for enforcement purposes is
done.
· From the entire range of indicators the most appropriate ones were
selected, e.g., for forest harvesting as presented in the following table.
·
Criteria for sustainable timber harvesting operations:
|
Criteria |
Indicator |
Specifications |
Mitigating measure |
|
The timber stand is able to recover by |
size-class harvested |
- trees >60 cm dbh and <120 cm dbh |
- tree marking |
|
means of natural regeneration |
trees retained (n/ha) |
- protected species (e.g., fruit trees) - 5 trees/ha; dbh>60 cm as seed source if regeneration in insufficient - potential crop trees (10-40 cm dbh) |
- tree marking |
|
Impact of felling operation limited |
felling damage |
<20% of the residual stem number |
- directional felling - no felling on slopes >25º |
|
Impact of yarding operation limited |
area of bare soil exposure |
<15% of harvesting area |
- tractor skidding only on slopes <15º - skyline systems on steeper slopes |
|
yarding damage1 |
<15% of the residual stem number |
- felling in herring bone pattern - bucking logs to length <= 8 m |
1Damage is define as an unrecoverable injury to a tree, so that it might die or be at least permanently devalued in its ecological or economic function
Palmer, J. and T.J. Synnott. 1992. The management of natural forests. In: Sharma, N.P. (ed.). Managing the World's Forests. Kendall/Hunt Publishing Co., Dubuque, Iowa. p.337-373.
· One of the many paradoxes of tropical forestry over
the past 30 years is that the rise in public interest has been paralleled by a
decline in the application of systematic management.
· Another paradox is
that the same period has seen a great increase in research on tropical biology
but little corresponding incorporation of research results into management
practice.
· The main reason forest management has failed in the past century
in the tropics has been the lack of any guarantee that forest would remain as
forest. The absence of security and tenure discouraged forest managers from
investing time and money in management for future production and often led to
such investments being lost.
· For example, in Queensland, the system that
had belatedly become the best managed and documented and most researched in the
world for management of tropical moist forest was closed down by a political
decision resulting from a state-federal struggle for supremacy and from a
failure of communication between foresters and conservationists.
· While the
merits of various forest management systems are being debated, tropical
silviculturalists are of one voice in advocating the use of reduced impact
logging techniques.
· The control of harvesting operations is the most
important condition for sustainable management after the long-term security of
the forest itself.
· Re-entry - the return of loggers to take previously
noncommercial species or sizes, which was demonstrated to be highly damaging to
regeneration more than 35 years ago - is still a problem in many countries.
Panfil, S.N. and Gullison, R.E. 1998. Short term impacts of experimental timber harvest intensity on forest structure and composition in the Chimanes Forest, Bolivia. Forest Ecology and Management 102 (2-3): 235-243.
· The harvesting intensity ranged from 1-6 trees/ha.
· The area of vegetation damaged by logging was a quadratic increasing
function of the harvest intensity.
· Both harvest mortality and total
mortality (trees harvested plus damage to the residual stand) were quadratic
increasing functions of harvest intensity when expressed in terms of basal area.
· The median distance to the nearest gap decreased from 24.9 m at a
harvesting intensity of 1 tree/ha to 8.3m at 6 trees/ha.
· The level of
damage to the residual basal area was very low because mortality was
concentrated on trees in the smaller size classes.
· Of three commercial
tree species surveyed, only the seedlings and saplings of Hura crepitans showed a significant positive
relationship between relative growth rate and harvesting intensity.
· Tree
species loss was relatively low and constant across a range of harvesting
intensities.
Pinard, M.A., F.E. Putz, J. Tay and T.E. Sullivan. 1995. Creating timber harvest guidelines for a reduced-impact logging project in Malaysia. Journal of Forestry 93(10): 41-45.
· Uncontrolled logging results in excessive damage to
the residual forest and reduces the forest's value for future timber production
(Ewel and Conde 1980).
· Sabah - 40% of the state area is designated as
commercial forest reserve, and all trees of commercial species (about 150
species) with a dbh of 60 cm or greater can be felled.
· Reduced Impact
Logging (RIL) to reduce damage to the residual stand and soil through good
inventory and mapping, pre-planning, pre-cutting of vines, directional felling,
good location of roads and skid trails, using the winch and skid pans/arches on
crawlers, and other environmentally sound management techniques.
· Typically
8-10 trees/ha removed (60-150 m3/ha/entry;
however, most typically 80-100 m3/ha extracted),
and an associated 40-70% of the residual stand is damaged.
· Vine cutting
reduces damage, reduces postfelling vine infestations, and increases light to
the forest floor before felling and thus smaller trees can adjust.
· Trees
uprooted in conventional logging 37%, while where RIL guidelines implemented it
was 13%.
· RIL areas skid trail coverage was 3.4% on average, where in
adjacent conventional logged areas it was 12% on average.
· % of trails with
soil exposed was 38% in RIL areas, while for conventional areas it was 87%.
·
RIL results in at least 50% less logging damage to soil and residual trees.
·
Felling rate slower in RIL due to marking and preparing trees for felling.
·
Planning and mapping cost more in RIL and map preparation accounted to 18% of
the cost of implementing the guidelines.
· RIL results in reduced bulldozer
maintenance cost (less sidecutting and blading, rough and rocky areas avoided,
and less driving), lower bulldozer skidding time, no need for enrichment
planting and logging cycle time can be reduced due to less damage to
residuals.
· Need for good training of all people involved from fellers to
technicians and foresters.
· Timber volumes extracted and logging damage in Sabah, Malaysia. Mean values (with SD) from four logging units of each logging method:
|
Logging Method | ||||
|
Conventional |
Reduced-impact | |||
|
Mean |
SD |
Mean |
SD | |
|
Logging intensity, trees/ha |
13.6 |
2.7 |
8.8 |
3.6 |
|
Logging intensity, m3/ha |
152 |
23 |
103 |
54 |
|
Proportion of area with soil disturbance |
0.17 |
0.02 |
0.07 |
0.03 |
|
Skid trail density, m/ha |
199 |
36 |
67 |
26 |
|
Proportion of trees killed during logging (5-60 cm dbh) |
0.41 |
0.11 |
0.15 |
0.07 |
|
Density of undamaged dipterocarp trees (5-20 cm dbh) |
49 |
24 |
104 |
62 |
Pinard, M.A. and F.E. Putz. 1996. Retaining forest biomass by reducing logging damage. Biotropica 28(3): 278-295.
· In the study logging intensity was 154 m3/ha (CL) and 104 m3/ha (RIL).
· In Sabah on average 8-15 trees/ha
are felled, which is 50-120 m3/ha logging
intensity.
· In conventional operations as much as 30-40% of the area is
traversed by crawler tractors (Chai 1975, Jusoff 1991), and 40-70% of the
residual trees are damaged (Fox 1968, Nicholson 1979).
· Typically, little
pre-harvest planning is carried out and the activities of fellers and bulldozer
operators are not well co-ordinated.
· No correlation was found between
volume removed and damage to residuals.
· First cuts in Amazonia usually
<50 m3/ha (Uhl & Viera 1989, Thiollay
1992, Verissimo et al. 1992).
· First cuts in Africa usually <30 m3/ha (Nwoboshi 1987, Ola-Adams 1987, Klo &
Ekwebelam 1987, Wilkie et al . 1992, White 1994).
· In conventionally logged
area 66% of residuals damaged, similar to other studies done in Sabah.
· RIL
27% of trees >10 cm dbh were damaged and 19% were dead within the first year
after logging.
· CONV 54% of trees >10 cm dbh were damaged and 46% were
dead within the first year after logging.
· Logging damage in RIL was 50% of
that in CONV.
· RIL had less severely damaged trees than in CONV (15% vs.
41%).
· Contains a table outlining in detail the RIL operations of harvest
planning, pre-felling vine cutting, skid trail planning, direction tree felling,
skidding, landings, and closing operations.
· More and larger trees remained
undamaged where RIL was practiced, hence future biomass increment and yields of
marketable timber are expected to be greater in the RIL areas than in the
conventional logging areas.
Pinard, M.A., B. Howlett and D. Davidson. 1996. Site conditions limit pioneer tree recruitment after logging of dipterocarp forests in Sabah, Malaysia. Biotropica 28(1): 2-12.
· In Sabah 30-40% of the area is churned or scraped by
bulldozers (Chai and Udarbe 1977).
· In heavily disturbed sites infestations
of twining vines, grasses and sedges can be extensive (Forestal International
Limited 1973).
· Trees >60 cm dbh logged and average volume removed 94
m3/ha.
· One landing established for each
25-50 ha block.
· Seed availability does not appear to limit the
establishment of pioneer trees in gaps, on landings, and on skid trails during
the first year after logging. Instead, recruitment appears to be limited by
unfavourable site conditions.
· Even in 15-year-old logged over forests of
Ulu Segama, the traces of log landings and skid trails are visible as treeless
patches and corridors.
· Improving harvesting practices to minimize the area
covered by landings and skid trails will be more effective management than
attempting to rehabilitate these areas following uncontrolled logging.
· The
broadcasting of pioneer seeds in recently logged areas may be a reasonable
management option for hastening tree cover in denuded areas, but only if it is
combined with site preparations that improve conditions for the survival of
pioneer tree species.
Pinard, M.A., Barker, M.G. and Tay, J. 2000. Soil disturbance and post-logging forest recovery on bulldozer paths in Sabah, Malaysia. Forest Ecology and Management 130: 213-225.
· The study was conducted in Eastern Malaysia.
· The
conventional timber harvesting system is based on a minimum harvesting diameter
of 60cm dbh.
· Prior to logging, forest structure and composition were
similar in the conventional logging and the reduced impact logging areas, with
mean basal area ranging from 25-33 m2/ha.
·
No difference could be found between the total volume of timber extracted per
logging unit for both conventional logging and reduced impact logging.
·
Timber volume extracted within the logging areas:
|
Logging area |
Volume extracted (m3/ha) |
Average excluding unlogged sections (m3/ha) |
Skid trail width (m) |
|
1976 Conventional logging |
93-118 |
136 |
3.9 |
|
1988 Conventional logging |
94 |
4.1 | |
|
1991 Conventional logging |
90-95 |
5.4 | |
|
1993 Conventional logging |
134-173 |
7.1 | |
|
1993 Reduced impact logging |
87-175 |
92 |
5.4 |
· In conventionally logged stands 59% of the residual
trees <60cm dbh were damaged.
· In areas logged with RIL techniques 29% of
the residual trees <60cm dbh were damaged.
· In conventional logging
operations, 140m2 of soil were disturbed per
tree harvested.
· In reduced impact logging operations, 94m2 of soil were disturbed per tree harvested.
·
Soil disturbance in conventional and reduced impact logging units:
|
Conventional logged units (% of total area) |
Reduced impact logging units (% of total area) | |
|
Skid trails |
4.7 |
3.3 |
|
Roads and Landings |
11.9 |
3.5 |
|
Total area disturbed |
16.6 |
6.8 |
· Types of soil disturbance recorded in conventional and reduced impact logging units:
|
Conventional logging units |
Reduced Impact Logging units | |
|
Area with sidecast soil (%) |
2.1 |
0.4 |
|
Skid trail surface area (%) |
9.9 |
3.2 |
|
Bladed |
87.7 |
37.7 |
|
Churned |
11.1 |
50.2 |
|
Compacted |
1.6 |
12.1 |
· Skid trails with intact topsoil and litter layer were
uncommon in conventional logged areas, but covered about 12% of the skid trails
in RIL units. In these compacted areas, saplings and vines resprouted soon after
logging.
· Soil disturbance was positively associated with harvested volumes
in conventional logging areas, but not in reduced impact logging areas.
·
The results of a time motion study conducted by Tay (1999) clearly indicated a
greater efficiency of skidding in RIL units compared to conventionally logged
areas. The skidding costs were US$ 1.98/m3 for
RIL techniques and US$ 4.51/m3 for conventional
techniques.
· The extent of soil disturbance found for conventional
harvesting techniques in this study was at the low end of the range of published
data for unsupervised logging in Malaysia, and was similar to values documented
for Suriname and Australia.
· The proportion of skid trails with subsoil
disturbance was less than half in RIL areas when compared to conventionally
logged areas.
· Four years after logging, woody plant regeneration was better
(more stems, greater species richness) in RIL than in conventionally logged
areas. Churned skid trails in general showed a greater regeneration potential
than bladed trails
· If disturbance of the soil is to be minimised, reducing
the area traversed by bulldozers will be more important than reducing the
traffic on any particular skid trail.
Pinard, M.A., Putz, F.E. and Tay, J. 2000. Lessons learned from the implementation of reduced impact logging in hilly terrain in Sabah, Malaysia. International Forestry Review 2(1): 33-39.
· The application of RIL techniques on 2,400 ha of old
growth dipterocarp forest in southeastern Sabah, Malaysia.
· The forests are
diverse in tree species and heavily stocked with trees of commercial interest;
the average basal area ranges from 25 to 33 m2/ha (dbh> 10cm), about 68% of this is in
commercial species.
· Conventional timber harvesting is based on a minimum
harvesting diameter of 60cm dbh. The management system is a modified uniform
system with a 60 year cutting cycle. Pre-harvest inventory and post-harvest
regeneration inventory are usually carried out. Other silvicultural treatments
such as climber cutting were dropped in the mid-1970s because high levels of
damage associated with harvest meant that only a small portion of the residual
forest warranted treatment.
· Timber volume extracted in RIL areas, when
expressed per net area logged, were about 70 % of the area extracted with
conventional techniques.
· Soil disturbance as a proportion of the total area
in the study areas:
|
Ulu Segama |
Kalabakan |
Gunung Rara | |||
|
RIL |
CL |
RIL |
CL |
RIL | |
|
Roads and landings (%) |
3.3 |
4.7 |
0.4 |
n/a |
1.2 |
|
Skidding trails (%) |
3.5 |
11.9 |
9.1 |
8.0 |
6.9 |
|
Area w/disturbed soils (%) |
6.8 |
16.6 |
9.5 |
10.2 |
9.3 |
[RIL = Reduced Impact Logging; CL = Conventional Logging]
· In general, the implementation of RIL reduced the soil
disturbance substantially when compared to conventional harvesting techniques,
both in terms of area damaged (from 13% to 9%) and degree of disturbance.
·
The implementation of RIL guidelines was associated with additional direct
operating costs of 135 $/ha or 1.27 $/m3 (Tay
1999).
· An additional 45 $/ha was spent on monitoring. A less intensive
monitoring program might be sufficient on an operational scale (Tay 1999).
·
In RIL areas the number of trees in the diameter classes >60cm and 10-40 cm
dbh was significantly higher than in conventional logging areas.
· Kleine
(1997) suggests that the difference in stocking levels combined with the higher
volume increment could translate into a reduction of the cutting cycle by
50%.
· Stand damage was generally within acceptable limits in RIL areas. The
exception was where clusters of trees had been felled. This resulted in
unacceptably large gaps.
· The damage to the residual stand could be reduced
from 50% to 28% of the original stems by implementing RIL techniques.
·
Skidding during wet weather periods resulted in deep tracks that could not be
drained, increased soil compaction and subsoil disturbance.
Plonczak, M. 1989. Struktur und Entwicklungsdynamik eines Naturwaldes unter Konzessionsbewirtschaftung in den westlichen Llanos Venezuelas (Structure and development dynamics of a natural forest under concession management in the western llanos of Venezuela). Gottinger Beitrage zur Land und Forstwirtschaft in den Tropen und Sobtropen, No. 43. 139pp.
· Study in Venezuela.
· Logging intensity 14-24
trees/ha >40 cm dbh (average 18.3 trees/ha with 15.2 m2/ha of basal area removed).
· Estimated rotation
age of individual trees of 80-100 years, a 20 year logging cycle is proposed
with the following limits: minimum felling dbh 40 cm; minimum of 30 merchantable
trees/ha of dbh >30 cm left after the cut; a residual b.a. of 15 m2/ha after the cut; maintaining b.a. maximum of 20
m2/ha to promote increment; and removing a
maximum of 7.5 m2/ha or a cut of 36 m3/ha at the end of the cutting cycle.
· 36 m3/ha logging intensity on a 20-year cutting cycle
(1.8 m3/ha/year MAI) of merchantable
species.
Plumptre, A.J. 1996. Changes following 60 years of selective timber harvesting in the Budongo Forest Reserve, Uganda. Forest Ecology and Management 89: 101-113.
· Measures of forest structure show that more than 50
years is required for the forest to recover to pre-logging levels.
· 428
km2 (42800 ha) of forest area.
· The total
volume of timber removed, mean volume per hectare and mean percentage of timber
that was mahogany per compartment in Budongo Forest for each decade since
1930:
|
Decade |
Total volume |
Logging intensity m3/ha |
Calculated area logged, ha |
Percentage mahogany |
|
1930-39 |
66 016 |
32.2 |
2 050 |
71.3 |
|
1940-49 |
170 080 |
42.9 |
3 965 |
68.3 |
|
1950-59 |
151 334 |
42.1 |
3 595 |
74.9 |
|
1960-69 |
247 110 |
25.1 |
9 845 |
65.8 |
|
1970-79 |
171 836 |
38.0 |
4 522 |
66.0 |
|
1980-89 |
66 251 |
24.9 |
2 661 |
61.9 |
· Volume harvested in 1940-50's peaked due to waiving of
the felling limit.
· Total area over the 60 years 26 638 ha or 62% of
forest.
· Those areas that had been logged and treated with arboricide did
show a greater tree species richness per unit area than the unlogged and
untreated areas (may be due to the succession towards monodominance that occurs
in Budongo).
Poore, D and J. Sayer. 1987. The Management of Tropical Moist Forest Lands: Ecological Guidelines. International Union for Conservation of Nature and Natural Resources, Gland, Cambridge, U.K. 63pp.
· Previous guidelines produced in 1976.
· In the 10
year elapsed no easing of the rate at which tropical forests are degraded or
transformed to other, often less sustainable uses. However, there has been a
great increase in knowledge and understanding of tropical ecosystems.
· A
well-managed tropical forest is a constantly self-renewing resource.
· The
greatest problem restricting benefits from tropical moist forests is careless
management for short-term profit.
· The greatest limitation to practicing
sustained yield management of tropical forests are inappropriate government
policies (which favour clearance followed by plantations) and the international
timber markets (which favour the logging of a relatively few species in tropical
forests).
· History has demonstrated that:
forest benefits are of value at all stages of economic development
forestry provides a good fulcrum for rural development
a well-managed forest (that is not restricted to the intensive production of only a few products) can respond to changing demands
· It is also generally accepted that:
the direct financial costs of many environmental problems caused by deforestation (such as flooding and soil erosion) are high
the values of non-marketed ecological benefits, such as climate regulation and the protection of downstream agriculture, may also be significant
· In timber mining operations it is usually the logging
companies which gain because stumpage fees are too low, governments do not
discriminate between species, licenses are based on volumes removed and not
merchantable timber in the tract, and leases to logging companies are far
shorter than timber rotations. All these factors encourage the loggers to abuse
the resource.
· Tropical soils are highly susceptible to degradation,
particularly if they are physically disturbed or exposed to sun or the direct
impact of heavy tropical rainfall.
· Plantations, agricultural lands,
pastures and modified forests often make less efficient use of nutrients present
in the forest, than natural ecosystems that have evolved there.
· Various
forms of the selective management system are now considered appropriate for
large areas of Asia and Africa. The degree to which they succeed depends upon
the care with which they are applied and the frequency of desirable species in
the original stand.
· The best specifications for management differ from one
forest to another. In some areas there is already sufficient knowledge for good
management. Elsewhere research is required, and until the information becomes
available, it is best to exercise caution.
· Management of natural forests is
preferred over plantations.
· Where options still exist countries should
attempt to derive the maximum of their timber needs from a managed `natural
forest estate'.
Pretzsch, J. 1997. Möglichkeiten und Grenzen der Bewirtschaftung von Tropenwald aus sozio-ökonomischer Sicht: Status quo und Perspektiven. Forstarchiv 68: 223-228.
· In general, it can not be assumed that timber
production in tropical forests is feasible in a sustainable manner considering
the ecological and socio-economic components of sustainable resource management.
· The implementation of low impact logging will increase the initial costs
of harvesting operations and therefore reduce the land value and revenue at
least on the short run.
Putz, F.E. 1985. Woody vines and forest management in Malaysia. Commonwealth Forestry Review 64(4): 359-365.
· in lowland dipterocarp forests in Malaysia, wood vines
increase damage associated with felling and slow rates of regeneration after
selective logging.
· vine cutting before felling should be done sufficiently
in advance so that the vines die and decay.
· this will reduce felling damage
and prevent vine sprouting after the logging operations.
Putz, F.E. 1994. Approaches to sustainable forest management. CIFOR, Bogor, Working Paper No. 4. 7pp.
· Claims of sustainability are virtually impossible to
prove but enough is known about tropical forest ecology and silviculture to
protect ecosystem functions and maintain biodiversity while still deriving
financial profit from logging.
· Lack of good management plans generally
results in logging practices that destroy natural regeneration and increase
forest susceptibility to soil loss, wildfires and weed infestations.
· To the
apparent surprise of some loggers the environmental benefits resulting from the
implementation of RIL are generally not expensive; harvest planning often
reduces the cost of transport logs from the forest to the log pond, mill or
port.
· There are also long-term benefits to the forest owner as less
severely damaged forest recovers more quickly after harvesting.
· In
dipterocarp forests in Sabah there is evidence that the directional felling
ability of a trained over untrained chain saw operator may be as great as 100
degrees.
· Where control is not exercised over bulldozer skidding 30-40% of
the area can be directly impacted in the removal of 10-12 trees/ha.
·
Avoidance of damage should be the primary objective of management.
· The
requirement of verifiable data on annual volume increments remains one of the
main stumbling blocks to be faced by forest managers who want their operations
eco-certified.
· The alternative to real and readily available growth and
yield data in Southeast Asia is the questionable assumption that trees in logged
but not silviculturally treated dipterocarp forests have a MAI of 1.0 cm/year
and that these unmanaged forests accumulate timber at an annual rate of 1.0
m3/ha/year. With proper management, these
increments and perhaps better are achievable. The problem is that based on these
assumptions in lieu of data, cutting rates that far exceed sustainable levels
are seemingly justified.
· Once good forest management guidelines are
developed and accepted, the next challenge is assessment of compliance.
Putz, F.E. and V. Viana. 1996. Biological challenges for certification of tropical timber. Biotropica 38(3): 323-330.
· Commercially-exploited forests are important
components of local, regional, and global conservation and development
strategies.
· Forest management can be more financially profitable, socially
beneficial, and environmentally acceptable than competing land uses.
·
Conversion of natural forest into pastures, plantations, and other non-forest
land uses is less likely where the forest has commercial potential.
· By
reducing the demand for and thus the financial value of forest products,
boycotts may increase the likelihood of forest destruction.
· If
conservation-minded consumers are willing to accept "organically certified"
exotic vegetables grown in fields that formerly were forests or savannahs, it
would be unreasonable for them to expect managed forests to be identical to
protected areas in composition and structure.
· Conservation biologists
interested in contributing to the forest certification process, however, may
have to reconcile their preservationist principles with the unavoidable impacts
of forest management. Whereas there is no inherent conflict between strict
preservation and management, saving every species everywhere is not an option
and neither is maintaining "pre-intervention" forest structure in forests
managed for timber.
Quirós, D., J.J. Campos, F. Carrera, F. Castaneda and R. aus der Beek. 1997. CATIE's experiences in the development of log impact forest harvesting systems in Central America. In: Proceedings of the FAO/IUFRO Satellite Meeting held in conjunction with the IUFRO XX World Congress, Tampere, Finland, 4-5 August, 1995, Research on Environmentally Sound Forest Practices to Sustain Tropical Forests. Food and Agriculture Organization of the United Nations. p.15-26.
· Generally 400 trees/ha with dbh >10 cm, and 40 of
these have a dbh >50 cm.
· Of the 40 trees with dbh >50 cm, 2-10
commercial trees/ha are removed in a typical cut.
· There can be between
100-150 tree species/ha.
· With increased wood scarcities in some parts
non-traditional species are being increasingly logged.
· Trees sold in many
cases at a very low price, just to get access to the forest so it can be
converted to other uses.
· Also, a problem due to government paperwork and
polices, which results in a lot of illegal logging.
· Lack of planning and
control in logging operations in Central America.
· In Costa Rica 36
different species are considered commercial (only 4.3% of the land area is still
forested).
· At the extreme Guatemala has vast forests and only two species
are extracted in logging.
· Lack of integration between logging and the
timber using industry, thus the industry has little incentive to control how the
logging is done (although it should because it will affect their long-term
well-being).
· The loggers only pay based on the volume removed, therefore
they only take out the best and largest logs. This results in over 20% of the
cut volume being unextracted.
· CATIE is basically another RIL system (good
map with tree locations is a basis).
· Cost of the detailed inventory is
$27.00/ha.
· Volume of unextracted wood, due to felling damage or poor
quality, can be from 20-25% of the extracted volume. This type of material is
suitable for supplying local market through small-scale sawmilling.
Rapera, R.B. 1978. Effects of logging on residual stands. BIOTROP Special Publication 3: 119-125.
· the success of selective silvicultural systems depends
very much on the quantity and quality of the future crop trees left after
logging
· The logger makes or unmakes the next harvest in the same area.
·
Width of logging roads varies from 5-10 m, with the right of way extending from
the road centre-line up to 15 m on both sides of main roads, and 10 m for spur
roads.
· In highlead settings, damage to residuals due to felling was 23-28%
and yarding damage 4-6%.
· In tractor skidding felling damage to residuals
was 9% and skidding damage 2%.
· The higher felling damage in the highlead
setting is probably due to working on steep terrain (>40% slopes), where
felled trees tend to roll more and thus cause more damage to residuals.
· The
growth rate of residual trees has been reported to be approximately 3.21 m3/ha/year.
· Growth rates from various research
results range from 1.60 m3/ha/year to 8.55 m3/ha/year.
Reid, J.W. and Rice, R.E. 1997. Assessing natural forest management as a tool for tropical forest conservation. Ambio 26(6): 382-386.
· Investments in "natural forest management" [NFM] are
financially unattractive and governments are generally unwilling or unable to
force loggers to make such investments.
· Most NFM initiatives can be
categorised as polycyclic felling systems. The cutting cycle is 25-40
years.
· In the case of primary forest, there is generally an initial
conversion phase in which the large volume of mature timber is harvested. In the
subsequent phase a constant, smaller amount of wood is cut at regular
intervals.
· Under conventional logging practices, little attention is paid
to the condition of the residual stand. This harvesting practice is
unsustainable, because the forest will not yield another harvest of the target
species for a long time, if ever.
· RIL is not necessarily an improvement
compared to conventional harvesting techniques. Where the topography is flat and
commercial trees occur at very low densities (sometimes less than 1 tree/ha is
extracted); conventional logging techniques may not cause avoidable damages.
Reitbergen, S. and D. Poore. 1995. Forestry and the increased use of lesser used species. ITTO, Tropical Forestry Update 5(2): 6-7.
· In management systems based on selective felling,
there are limits to harvesting intensity above which felling and skidding damage
will be so high as to jeopardise the forest's regenerative capacity, no matter
how well-planned and executed the operation.
· The figure of 10 trees/ha has
been quoted as an order of magnitude for such an upper limit, and it is probably
true that harvesting more than 10 trees/ha without seriously endangering a
stand's future potential demands planning and operational skills beyond the
current capacity of most concessionaires in the tropics.
· It is impossible
to set universal threshold values for logging intensity: 1) damage to the
remaining stand depends much more on management variables such as skid trail
planning and machine operator skills than on the number trees harvested; and 2)
acceptable damage limits vary according to the physical and biological
characteristics of the forest site under consideration and the management
objectives that have been set for it.
· In many forests in South America, e.g., the quantities
of valuable timber species capable of responding to fairly heavy canopy opening
appears to be restricted, whereas in Southeast Asia and Africa heavier canopy
opening is almost always desirable.
· Increased harvesting of lesser used
species seems to be a two-edged sword: it may have a positive or a negative
impact on benefits derived from any given tropical moist forest, depending on
the site characteristics, the management objectives chosen and the standard of
forest management.
Reyes, M.R. 1978. Possibilities of increasing yields of
tropical rainforest in the Philippines. The Malaysian Forester 41(2):
167-170.
· General logging performance up to the present results in
secondary growth that is below the optimum potential of the forest.
· To have
more young trees left uninjured after logging requires the training of fellers
in felling techniques and yarding crews in yarding and skidding techniques, all
with the objective of minimizing destruction and injury to young trees.
·
Growth plots in residual stands in Eastern Mindanao show a total volume of 90
m3/ha just after logging, whose predicted volume
30 years after logging is about 260 m3/ha of
which the harvestable volume of trees reaching 60 cm dbh and over is 160 m3/ha (2.33 m3/ha/year).
· With a 20% increase in residual
stand the harvestable volume is increased to 190 m3/ha (3.33 m3/ha/year).
· A simulation projection of a treated
(stand improvement through cleaning, thinning and release), second growth,
logged-over dipterocarp forest in Eastern Mindanao shows a yield of 260 m3/ha, 30 years after logging, compared with a yield
of 176 m3/ha in an untreated selectively logged
area (increase of 44%). On a 40-year cycle the treated stand is projected to
yield 375 m3/ha compared to 182 m3/ha in the untreated stand (increase of 89%).
Reyes, M.R. 1983. The selective logging system and its viability. The Philippine Lumberman 29(1): 20-30.
· Selective logging has been shown to be simple, logical
and financially feasible by a few conservation-minded concessionaires.
·
However, it has been a hard sell, perhaps because: excessive economic
motivation; prejudice; vestiges of colonial mentality; dominance of
concessionaires; lack of guts, dedication and sustained forestry leadership in
an adverse society and political environment; and moral decadence.
· Found in
field studies in 1950's that 58% or more of the young trees could be saved by
the loggers using their ingenuity to avoid hitting marked young trees.
·
Paper presents a stem distribution chart showing stocking levels by diameter
class to ensure successful regeneration of dipterocarp forests using selective
logging.
· Average growth rate used in calculations is 3 m3/ha/year and the cutting cycle is 35 years.
·
There are a few licensees who have fairly good residual forests.
· We find
more of the inadequately stocked logged-over areas due to allowing logging as
the loggers please.
· Empirical evidence shows that the old growth sawtimber
cut may vary from 60 to 180 m3/ha, but based on
the prescriptions for the new selective logging system the yields may only be 30
to 90 m3/ha.
· It has been shown that
permissible cuts at the end of the cutting cycle of three study areas were
almost equal if not greater than the average cut from the old growth (when
selective logging was done properly).
· In one company where recently
supervised logging was conducted, about 70% healthy residuals were
achieved.
· There is a noticeable shift in attitude from predominantly
exploitative-oriented to conservation-oriented logging.
Ruslim, Y. 1992. Tropenwalderschliessung in Indonesien, am Beispiel der Forstkonzession PT.ITCI in Ostkalimantan. Master of Science-Thesis. University of Göttingen. 1992. 85pp.
· The cutting cycle for the Indonesian Selection Cutting
System is 35 years with a minimum residual density of potential crop trees of 25
trees/ha.
· The area affected by skidding ranged from 11.1% to 13.4% of the
total area.
· The initial basal area was 33.19m2/ha. The residual basal area was 14.5m2/ha (44% of initial basal area) of undamaged and
8.58m2/ha of damaged trees.
· For a second
site the initial basal area was determined as 103.63m2/ha, with a harvesting intensity of 39.1m2/ha (approximately 33% of the basal area). 19% of
the residual stand were damaged during felling and skidding operations. 44% of
the initial stand remained undamaged after harvesting.
Ruslim, Y. 1994. Der Beitrag eines planmässigen Erschliessungs- und Nutzungskonzeptes zur pfleglichen Holzernte im tropischen Regenwald, untersucht am Beispiel eines Dipterocarpaceenwaldes in Ostkalimantan, Indonesien. Dissertation. Universitaet Goettingen. 1994. 139 pp.
· This study was carried out in eastern Kalimantan,
Indonesia.
· The cutting cycle for the TPTI system (selection system with
supplementary planting is set to 35 years. 20 trees of merchantable size (dbh
_50cm) per hectare must be retained.
· On average 13.5% of the area were
affected by skidding (on 8.7% of the area the topsoil was exposed).
· Damage
to the residual stand by felling and skidding:
|
Moderate slope |
Steep slope | |||
|
Basal area |
Basal area | |||
|
(m2/ha) |
(m2/ha) |
% |
(m2/ha) | |
|
Basal area prior to harvesting |
22.03 |
100 |
25.43 |
100 |
|
Harvest |
7.11 |
32.27 |
7.02 |
27.60 |
|
Felling damage to crowns |
1.59 |
7.22 |
2.69 |
10.58 |
|
Felling damage to stems |
3.79 |
17.20 |
2.63 |
10.34 |
|
Skidding damage |
0.93 |
4.22 |
2.20 |
8.65 |
|
Sum of damaged trees |
6.31 |
28.64 |
7.60 |
29.88 |
|
Basal area of undamaged trees in the residual stand |
8.61 |
39.08 |
10.81 |
42.51 |
· With both ground conditions (moderate and steep
slopes) felling and skidding damage amounted to 30% of the initial basal area.
· On most sites between 20 and 40% of the potential crop trees were damaged
during harvesting operations.
· Between 6.9% and 9% of the area were
affected by equipment movement.
· On moderate slopes an average of 189 m/ha
of skid trail were constructed with unplanned logging compared to 260 m/ha in
planned operations.
· On steep slopes an average of 216 m/ha of skid trail
were constructed with unplanned harvesting compared to 280 m/ha in planned
operations.
· Winching of logs to the skid trail was not possible due to the
large volumes harvested per stem.
· Severe soil damage can be reduced
significantly by implementing reduced impact logging techniques.
Ruslim, Y., Hinrichs, A. Sulistioadi, B. and PT Limbang Ganacea. 2000. Study on implementation of reduced impact logging. SFMP Docoment No. 01a.Ministry of Forestry and Estate Crops in Cooperation with Deutsche Gesellschaft für Technische Zusammenarbeit.
· This study was undertaken in the district of east
Kalimantan, Indonesia at the location of salvage felling operations in virgin
forest that had been burned slightly.
· The purpose of this study was to
compare the effects of reduced impact logging [RIL] and conventional logging
[CL].
· In general the stand condition was quite good even though it had been
burned during the 1997/1998 fires. The potential for timber harvest was still
high.
· The results of stand inventories indicated that 15-20 trees of
commercial species could be harvested with an estimated volume of 70-90 m3/ha.
· During the study the amount of trees
felled was limited to 12 trees/ha with a volume of approximately 75 m3/ha. It was felt that this was representative of
heavy logging intensity.
· The study results would also be applicable in
unburned forest, because the condition of the study area was that of an almost
pristine forest.
· For felling activities there was no significant difference
in work time and productivity. However, the work time per element (e.g.
preparation for felling, bucking) was quite different.
· By implementing RIL
procedures productivity in pure skidding was reduced by 34% (winching to a
maximum of 30m, two helpers available) or 29% (winching to a maximum of 15m, one
helper available) respectively.
· Due to the fact that a lot of time is
usually lost due to machinery problems, bad weather and breaks, the overall
reduction in skidding productivity per day was approximately 15% compared to CL
operations.
· In the RIL units, harvesting caused less opening up of the
canopy by a factor of 22% (winching maximal 15m) to 29% (winching maximal
30m).
· Level of opening up average/ha resulting from felling and skidding:
|
Parameter |
RIL |
RIL (winching max. 15m) |
CL |
|
Skid trails (m2/ha) |
554 |
726 |
1632 |
|
Percentage |
5.5 |
7.3 |
16.3 |
|
Falling Trunks (m2/ha) |
139 |
139 |
137 |
|
Percentage |
1.4 |
1.4 |
1.4 |
|
Falling canopy (m2/ha) |
1180 |
1180 |
860 |
|
Percentage |
11.8 |
11.8 |
8.6 |
|
Opening up (m2/ha) |
1873 |
2045 |
2629 |
|
Percentage |
18.7 |
20.4 |
26.3 |
· The impact of harvesting was high as after felling
less than half of the residual stand >20cm dbh remained undamaged. The damage
to the residual stand caused by felling was not significantly different between
the two harvesting systems.
· The percentage of healthy trees in the residual
stand could be increased from 35 to 47% by implementing RIL techniques
(reduction by 28%).
· The chainsaw operators for both harvesting techniques
were training in reducing waste. Nevertheless the exploitation factor in the RIL
plots was greater (85%) than in the CL plots (81%). Using CL techniques most of
the timber losses were due to logs left at the felling site as well as
inefficient bucking.
· Timber utilisation in RIL operations was still less
than optimal (stumps were cut too high, lengths above the first branch were not
utilised).
· The operational costs for the tractor were reduced by 5% per
months by implementing RIL (due to a reduction in work time for the tractor
working with a heavy load).
· Comparison of forest harvesting operational
costs using RIL and CL procedures (estimation of harvesting intensity = 48 m3/ha):
|
Conventional Logging (US$/m3) |
Reduced Impact Logging (US$/m3) | |
|
1. Planning Section |
||
|
· Pre-harvest stand inventory [ITSP] |
0.09 |
- |
|
· ITSP and topographic survey |
- |
0.05 |
|
· Planning/ mapping of skid trails |
0.01 |
0.01 |
|
· Marking skid trails |
- |
0.08 |
|
Total (US$/m3) |
0.10 |
0.24 |
|
2. Production and Equipment Section |
||
|
· Opening up skid trails and "closing up" |
- |
0.35 |
|
· Felling |
0.23 |
0.23 |
|
· Conventional skidding |
2.45 |
- |
|
· RIL skidding |
- |
2.75 |
|
Total (US$/m3) |
2.68 |
3.33 |
|
Total (US$/m3) |
2.78 |
3.56 |
· Using RIL techniques results in an increase in
operational planning costs by US$ 0.14/m3 and an
increase in the overall operational production costs of around US$ 0.14/m3.
· Overall the RIL system was by US$ 1.00/m3 more expensive than the conventional harvesting
system.
· Condition of the residual stand:
|
CL |
RIL | |
|
1. Stand condition after harvesting |
||
|
· Healthy trees, dbh 20-40cm |
22 m3/ha |
25 m3/ha |
|
· Healthy trees, dbh > 40cm |
76 m3/ha |
100 m3/ha |
|
2. Regeneration potential |
||
|
· Enrichment planting/ Rehabilitation |
Necessary on skid trails and landings |
Only necessary on landings |
· It is expected that the second harvest in the RIL
plots could be undertaken within a shorter time frame.
· In areas with a
lighter harvesting intensity or with more difficult topographic conditions RIL
proved to have a higher increase in work efficiency (for felling) than found in
this study.
· Under CL it was common for the tractor operator to skid two
logs at once. With RIL this was rarely done in order to minimise damages to the
residual stand.
· The implementation of RIL caused a decrease in skidding
productivity by 15% per month due to additional time required for winching and a
reduction of combined loads.
· Under RIL it is estimated that the chainsaw
operator will have sufficient time for cross cutting trees that have fallen
across the skid trail and are difficult for the tractor operator to position for
extraction. This would help to reduce opening up resulting from skidding.
·
Implementation of RIL reduced the overall opening up by 29%, the greatest
reduction occurred due to the smaller size of the skid trails (55%
reduction).
· Directional felling is very difficult, especially for trees
that have a natural lean and/or are very large (dbh >70cm). Generally a wedge
is only used for directing the fall of smaller trees and to avoid breakage of
the log when cross cutting. Therefore the damage level to the residual stand
could not be reduced significantly by implementing RIL techniques.
·
Frequently logs bucked by the chainsaw operator where still trimmed further at
the log landing or at the log yard. Therefore, to avoid that parts of the logs
they deliver not being used, "waste" that is actually still utilisable was cut
and left in the forest.
· The utilisation of timber above the first branch
could be increased (often about 4-6m of utilisable timber were left
behind).
· The increased operational costs associated with RIL were covered
directly by the financial gains of increased timber utilisation. At the given
harvesting intensity the timber production could be increased by 2 m3/ha through better utilisation standards.
·
Implementing the entire process of RIL under the conditions of this case study
led to a direct financial benefit of US$ 50 per hectare, if the company had been
allowed to harvest the "additional timber" under its given AAC.
· There are
also long term benefits of an increase in quality of the residual stand, reduced
need for rehabilitation and the possibility of shortening the cutting cycle.
Sargent, C., T. Huszin, N.A. Kotey, J. Mayers, E. Prah, M. Richards and T. Treue. 1994. Incentives for the sustainable management of the tropical high forest in Ghana. Commonwealth Forestry Review 73(3): 155-163.
· Incentives may be thought of as signals. They may be
negative - disincentives - providing an alert or deterrent, or they may be
positive, motivating and indicating action.
· Incentives are bad if they are
unclear, contradictory, perverse or lead to market distortion.
· The majority
of existing market and fiscal incentives (demand side incentives) encourage and
promote extraction of high value species; while control (supply side) measures,
including management plans, yield allocation and so forth, attempt to conserve
high value species, promoting extraction of a wider range of lesser used
species.· Field work and analysis fully supported the hypothesis that demand
side incentives would be ineffective, and even deleterious, without attention to
supply side issues.
· The sharing of management will be essential. Industry
will need to accept a far greater responsibility for the resource if current
predictions of the extinction rate of key economic species are to be
averted.
· Good forest management requires technical knowledge of the
resource.
Sarre, A. 1995. Opening the door to lesser used species. ITTO, Tropical Forest Update 5(2): 1
· Increasing the use of lesser used species is seen by
many as a way of making natural forest management more viable.
· First, by
harvesting more volume per hectare, the same quantity of wood will be produced
from less area, leading to the possibility that less forest area will be
logged.
· Second, and more important, generating more revenue from a given
area will increase the value of the forest and therefore its attractiveness as a
long-term land-use option.
· Arguments that increasing logging intensity will
cause more environmental impacts, and the economics of increasing the range of
species used are yet to be proven.
Sarre, A. 1996. What foresters can do. ITTO, Tropical Forest Update, 6(3): 1
· The single most important thing that foresters can
change is the way that forests are logged.
· There is no doubt that most
current logging techniques cause unnecessary damage to the forest.
· Even
without reducing volume cut, better logging techniques will have an immediate
positive effect on the post-harvest value of the forest and will increase the
long-term chances of sustainability.
Saulei, S. 1984. Natural regeneration following clear-fell logging operations in the Gogol valley, Papua New Guinea. Ambio 13(5-6): 351-354.
· Clearfelling was not as disastrous as may people
predicted.
· Within a few months after felling bare ground was covered with
natural regeneration, but new growth was less diverse.
· In the clearfelled
area soil phosphorous was 50% of that in closed forest (11.60 ppm vs. 22.00
ppm).
· Compacted tractor trails and landings, and denuded slopes and
hilltops developed in many cases into grassland.
Sayer, J.A., P.A. Zuidema and M.H. Rijks. 1995. Managing
for biodiversity in humid tropical forests. Commonwealth Forestry Review 74(4):
282-287.
· Logging cycles 20-40 years with fewer trees removed rather
than a very intensive cut every 70-80 years.
· Low intensity logging also
protects sensitive understory species (plants, mammals, birds).
· 15.35% of
all trees damaged in polycyclic harvesting, vs. 40-60% damaged in monocyclic
systems (Bruijnzeel 1992).
· Low impact logging techniques are not difficult
to implement and may be cheaper than conventional logging practices.
Sayer, J.A. and R.N. Byron. 1996. Technological advance and the conservation of resources. Int. J. Sustain. Dev. World Ecol. 3: 43-53.
· In recent decades, forest industries have placed a
high premium on uniformity in the dimensions and physical properties of
wood.
· New technologies for transporting and converting heavy hardwoods have
radically changed the situation - plywood mills in the Amazon have already
captured a major share of an international market where South-east Asia had
previously expected to retain a long-term competitive advantage.
· Rapid
progress in technologies to produce composite wood products (MDF, OSB, LVL,
etc.), technologies to pulp mixed tropical hardwoods and the emergence of
hardwood chips as a major international traded commodity for both industrial raw
material and fuel, will result in changes.
· Distance to market will become
more important, rather than the quality of the fibre in the forest, as a result
remote forests will loose their commercial attractiveness.
· The special
qualities and dimensions of timber from old-growth forests will no longer
justify the high extraction costs if an industry can make similar products using
diverse timbers from more accessible, second cycle forests.
· Argued there
will always be a demand for high-value, decorative cabinet veneer and other
specialty timbers - however, this will be a small fraction of total trade and
the increasing availability of attractive alternatives from temperate forests
may restrict this part of the tropical timber industry.
· Growth in domestic
demand is likely to outstrip demand for internationally traded products in
countries such as China, India, Brazil and Indonesia.
· As these countries
develop their remote areas for agriculture and minerals will push roads and
railways out to the fringes, thus making the cost of timber removal competitive
again.
· This will in the end increase the pressure on remote forests, as
opposed to export based economies.
· The average annual timber productivity
of natural forests, world-wide, is currently just under 1 m3/ha/year; thus 4 billion hectares presently yield
approximately 4 billion m3 - a volume which
could be hypothetically produced from 100 million hectares of tropical
plantations.
· By portraying export-led industrial forestry as the primary
threat to forest conservation (e.g., Dudley et al.,
1995), the environmental community is `shooting itself in the foot'.
Sayer, J.A., J.K. Vanclay and N. Byron. 1997. Technologies for sustainable forest management: challenges for the 21st century. CIFOR, Occasional Paper No. 12. 11pp.
· Anticipate changes in:
production shifting from native forest to plantations
technological developments allowing more efficient processing, less waste and more recycling
end-use products becoming less dependent on the specific wood characteristics of raw materials
demand increasing, but fluctuating according to technologies in non-forest sectors
better information for decision makers, through the integration of remote sensing, GIS, and other technologies into decision-support systems
more rapid shifts in loci of production and transformation as industries seek out areas of comparative advantage
more pragmatic and efficient options for conserving biodiversity
· Technologically there is no reason why plantations
cannot supply most of the world's wood requirements by early next century.
·
Demand for the few specialty products that can be obtained only from natural
forests may not increase greatly, and can probably be satisfied from
ecologically sensitive logging operations in areas where forests are retained
primarily for their environmental and amenity functions.
· Conclude that the
frontier logging of relatively remote areas in the tropics, which has been a
prominent feature of the timber industry in the late 20th century, may become
less important in the future.
· Technological problems which made the more
highly diverse and higher wood-density timbers of Papua New Guinea and South
America less attractive in the past have largely been solved.
· Expect the
natural forests to become less able to compete with outputs of the rapidly
expanding plantation sector in the tropics and subtropics. In contrast to rising
costs and declining quality of logs from natural forests, the volume and quality
of plantation material will continue to improve while technological advances in
plantation silviculture and wood processing continue to lower unit production
costs.
· The search continues for technologies to make high-value products
out of cheap and more readily available fibre.
· At present 15% of the
world's industrial wood production comes from 25 million ha of fast growing
plantations, located in both tropical and warm temperate countries. High-yield
forestry is a reality and the biological ability to shift most wood production
to plantations exists and can be put into practice if prices of industrial wood
rise high enough to justify it.
· It seems unlikely that logging of natural
forests will disappear completely (COMMENT: this would be a catastrophe since
the forest would have no value and thus would get replaced or destroyed for
other use).
· Timber revenues represent the usual way to finance the
maintenance of many other forest services.
· Wood productivity in natural
forests ranges, in most cases, between 1-3 m3/ha/year.
· In plantations growth rates of 20
m3/ha/year are now routinely achieved with some
tropical and subtropical fast-growing species, while some industrial plantations
of the tropics and subtropics exceed 30 m3/ha/year operationally.
· There is a strong case
to be made for further refinement of the reduced-impact logging (RIL)
technologies.
· Most of the techniques embodied in RIL are not new, the
innovation relates to the economics of using these technologies and to policies
and incentives to promote their adoption.
· Increased use of these techniques
should lead to a reduction in environmental impacts and greater productivity
during future cycles.
· Thus there is scope to promote gains to be attained
by reducing damage to trees and to the soil, by minimizing breakage and waste,
and by reducing capital and operating costs of machinery.
· Developments in
the wood processing industries may contribute to greater efficiency and less
waste in both the factory and the forest.
· Recent reviews of the extent to
which biodiversity can persist in logged forests further strengthens the case
that most of the world's forest biodiversity can be retained without the
draconian restrictions on all forest use that have often been the rallying cry
of the conservation community.
Scharpenberg, R. 1997. Forest harvesting in the natural forests of the Congo: case study.
Food and Agriculture Organization of the United Nations, in print. 68pp.
· The report presents findings of a case study on forest
harvesting in natural forest of the Congo. It is part of a series of case
studies published by FAO in the field of forest harvesting.
· The overall
objective of the study is to contribute to the development of sustainable forest
management in the tropics through the establishment of credible data on forest
harvesting practices and harvesting impacts in tropical high forests.
· The
study aims at the establishment of reliable data on a ground harvesting system
in the tropics, using power saws, crawler tractors and wheeled skidders.
·
The study has been carried out in co-operation with a large private contractor
operating a concession in the Republic of Congo: about 150000 ha of
closed-canopy, broad-leaved forest located in the Chaillu Massif in southern
Congo, at the border to Gabon; annually harvest area is about 15000 ha; and
average annual rainfall in the region is about 1800 mm.
· The case study
consists of a study inventory, a harvesting performance study and a harvesting
impact assessment. The size of the study area is 150 ha, subdivided into
three harvesting compartments of 50 ha each. The terrain is slightly
mountainous, with water courses and seasonal swampy areas between
elevations.
· The average harvesting intensity is only 5-6 m3/ha (about 1 tree/ha). The main commercial species
is Okoumé (Aucoumea klaineana), which is a medium
density timber and is used for the production of peeled veneer, mainly for
plywood. The low concentration of harvestable trees plays an important role in
harvesting efficiency and site impact.
· The study inventory of all trees
revealed an average density of 455 trees/ha greater than 10 cm dbh, of
which 3.3% (15 trees/ha) are Okoumé. The proportion of Okoumé significantly
increases in the higher diameter classes. During harvesting operations, all
Okoumé trees above 80 cm dbh and showing adequate stem quality are felled
and removed.
· The volume of 96 Okoumé logs from 93 trees harvested in the
study area was computed in order to establish losses during felling and bucking.
The average net volume of all 96 logs is 5.8 m3; the total recovery, expressed as net log volume
compared to the standing stem volume (including stump, up to the first branch of
the crown) is 70%.
· Out of the study area, three well defined stands
totaling 59.5 ha were selected for the harvesting impact assessment; the
total wood volume felled and removed from this area was 345.6 m3 net log volume, with an average skidding distance
is 403 m. Crawler tractors were used for short hauls and for concentrating
logs, while wheeled skidders were used for the long haul to the landing.
·
Damages to the residual stand occur during felling, skid trail construction and
log skidding, and were classified for study as: crown damages, bark damages and
uprooted or broken trees. - felling damages were recorded on 30 felling
sites. The average damage frequency was 17.7 trees damaged per felled tree
(3 trees damaged/m3). Damage to residual Okoumé
trees was 3.3% with the majority of damaged stems in the higher dbh classes. The
total felling damage for all trees was 17.3 trees/ha.
· Skidding damage
occurred with an average frequency of 11.5 trees/ha. The proportion of
Okoumé damaged by skidding was 2.8%. On average 212 trees/km of skid trail were
damaged, of which 5.9 are Okoumé, again concentrated in the higher dbh classes.
46% of all skidding damaged trees were fully or partly uprooted. The average
number of skidding damages per felled tree is 11.8 (2 damaged trees/m3).
· In total, the number of felling and skidding
damages per hectare was 29 (30 damaged trees/tree felled or 5 damaged
trees/m3 extracted).
· The overall damage
frequency for Okoumé in all diameter classes was 7.2%, and of trees
40-80 cm dbh (immediate future crop trees) it was 9%. The damage frequency
for all species and size classes was 6.3%.
· The soil disturbance survey
revealed a total disturbed area of 8.4% of the annual coupe area: felling sites
3.8%, skid trails 2.7%, secondary roads 1.0%, primary roads 0.7%, and landings
estimated 0.2%. Other facilities such as workers' camps, workshops and the
private airport are not regarded since they are used as the infrastructure of
several annual coupes. A more detailed soil survey on felling sites, skid trails
and landings, using two disturbance classes (depending on whether mineral soil
is slightly or fully exposed), shows that 0.9% of the annual coupe is seriously
disturbed by skid trails and landings and other 5.8% is slightly disturbed by
felling sites and skidtrails.
· Under the prevailing conditions, the
observed forest operation could be called "low impact" by definition due to the
low removal rate of approximately 1 tree/ha. However, as with any harvest
operation, further toward the objective of sustainable forest practice are
possible, by placing high priority on harvest planning and assessment.
Schmidt, R. 1987. Tropical rain forest management. Unasylva 39(156): 2-17.
· Productive management of many humid lowland forests is
both technically feasible and economically viable.
· Plantations yield great
benefits but cannot replace the functions of current natural forest areas, they
are complementary with each one supplying different products and most applicable
to different types of terrain.
· The average dbh increment in natural
tropical forests varies with many factors, but is seldom greater than 1 cm/year
and is often less.
· Thus if crop trees were 10 cm average dbh, a minimum of
40 years might be expected to maturity - if larger trees can be successfully
released, logging might occur every 25-30 years.
· A forest inventory in
Brazil found that the forest contained 54 m3/ha
of stems >45 cm dbh, of this 36 m3/ha were of
28 commercial species - the experiment extraction produced 72 m3/ha of which 64 m3/ha were commercial.
· In Peru the VAC started at
15 m3/ha (15 commercial species), but increased
to 30 m3/ha during the study as 20 more species
became commercially viable (5 year project).
· Inventory projects in Colombia
indicated 114 m3/ha of total stem volume and 33
m3/ha of commercial volume.
· In Suriname
planned skidding trails and improved felling techniques to reduce damage to
remaining trees and also reduced extraction costs - with some improvements in
forest management it was predicted that 40 m3/ha
could be obtained on a 20 year logging cycle with 13.5 trees/ha being
commercial.
· In Africa the net volume of logs extracted varies from 5 to 35
m3/ha.
Schoening, J.R. 1978. Forest industry development in Southeast Asia: one company's experience and observations. In: Proceedings of Conference on Improved Utilization of Tropical Forests, May 21-26, Madison, Wisconsin. USDA, For. Serv., Forest Products Lab. p.159-164.
· Paper mainly about Weyerhaeuser's experience in
Indonesia.
· Rainfall 250-350 cm/year and periods of rain for 30-60 days can
stop operations completely.
· Need to ballast all major haul roads with
crushed rock.
· Built all supporting infrastructure for a community in the
license including housing, schools, hospital, stores, places of worship,
recreation, treated water, sewage disposal and electricity.
· Good
utilization of all species and log grades (quality) is the cornerstone of
intelligent forest resource development and long-term management.
· In
traditional operations forest stands with gross volumes of up to 150 m3/ha produced utilized volumes as low as 20 m3/ha.
· On a historical basis, the forest products
industries in every country have followed a trend from very poor utilization, in
early stages of development, to a very high utilization level as industry and
the economy matures.
· As a log producer the utilization level could be
improved through employing proper logging techniques, transportation facilities,
and development of markets.
· Weyerhaeuser improved utilization to 60-75
m3/ha by utilizing sinkers (10% of potential
commercial species) by employing barges, developing markets for excellent
quality lesser known species, and by utilizing marginal quality logs.
· A
typical stand would consist of 77 m3/ha of all
species over 50 cm dbh.
· A dirt road logger (seasonal) would extract 36
m3/ha (47% of potential volume).
· A dirt
road logger operating as a contractor on a licence would extract 45 m3/ha (58%).
· An all-weather logging operation
(good infrastructure gives the ability to improve utilization and also needs the
better utilization to cover fixed costs) would extract 65 m3/ha (84%).
Seppanen, H. and J.D. Malvas. 1986. Case study on self-loading winch trucks in the tropical high forests of Viet Nam. Food and Agriculture Organization of the United Nations, UNDP/FAO VIE/80/019, FOPH 1986/2. 24pp.
· Tropical low elevation and flat dipterocarp forest in
southern Viet Nam.
· Stand volume in trees >50 cm dbh was 54 m3/ha (19 trees/ha), with the dominant tree size
falling within the 50-59 cm diameter class.
· The minimum cutting diameter
was 50 cm and 8 trees/ha could be removed (leaving 11 to 12 trees/ha >50 cm
dbh as residual seed trees for future harvests).
· Chain saw felling with
tree-length skidding to landings.
Serna, C.B. 1986. Degradation of forest resources: Asia-Pacific Region. Food and Agriculture Organization of the United Nations, GCP/RAS/106/JPN, Field Document 15. 34pp.
· The selective logging that is practiced in most
tropical forests in Southeast Asia can, if properly carried out and supervised,
minimize the damage to the soil.
· Projected harvest volume in the second
cycle cut will be considerably lower than in the old growth forests (e.g.,
Taguda (1977) estimated 83.2 m3/ha (44.5% less)
available 35 years after first selective logging; and Bryan and Agaloos (1965)
projected 63.6 m3/ha (36 % less) 40 years after
the first selective cut).
· Although some damage is expected in selection
logging, excessive damage results from:
selection and marking of trees to fell and retain is made haphazardly, if done at all
lack of supervision in felling and off-road transport
rough topography and use of too powerful skidding and yarding equipment
payment structure encourages felling and yarding production, and does not give sufficient compensation for minimizing damage to residuals or environment
· An additional source of damage that has been
increasing alarmingly, at least in the Philippines, is illegal cutting.
· The
end to the problem of illegal logging is nowhere in sight. In fact, it has been
aggravated to the extent that it is now causing havoc in forests, especially in
the residual dipterocarp forests logged under a selective system.
· In the
Philippines strict guidelines are prescribed for selective logging and the use
of devices to minimize damage in felling and yarding is required; however,
proper supervision is lacking in most cases.
Silitonga, T. 1987. Wood residue identification at originating points of Indonesia. Special country report prepared for the Programme on Wood Residues Identification at Originating Points of the Food and Agriculture Organization of the United Nations, The Republic of Indonesia, Department of Forestry. 42pp.
· Average road density of 15-20 m/ha is acceptable.
·
Cat D7 or D8 with experienced operators used for road construction.
·
Generally there is no pre-planning of skid trails.
· Skid trails are usually
established by skidder operators and their assistants who also help in locating
and establishing skid trails towards the densely stocked sections of a
block.
· Felling done at 1.3 m from the ground (high stumps) on all marked
trees >50 cm dbh.
· For trees with buttresses, the felling cut can be 20
cm above the main buttress.
· Diameter at which topping occurs depends on
market conditions.
· Study 1 - wastewood was 12% & 22% stemwood in
cut-over, 11% & 17% left at collection sites.
· Study 2 - 12% & 18%
waste in felling and bucking areas, 2.9% & 2.5% in log yard.
· Broken and
defective logs were the major part of the woodwaste, and accounted for 15.5%
when calculated on a clear bole basis and slightly higher at 17.5% when based on
minimum 30 cm diameter.
· Study 3 - wastewood based on a clear bole basis was
found to be 25.1% for Kalimantan and 21.9% for Sumatra (less here because closer
to market, therefore, higher utilization rate).
· Study 4 - the average
wastewood was 19 m3/ha (wastewood defined as:
(1) part of the felled trees (stump, clear bole stem, etc.,); (2) defect trees
due to improper felling; (3) the trees destroyed by tractor skidding. The
minimum length considered was 1 m and minimum diameter was 10 cm inside bark.) -
the lower value is due to omission of short under 1 m long waste. Study was done
in Sumatra.
· For clear bole the wastewood in tropical rain forest is from
24-26% (based on (stumpage volume - extracted volume) / stumpage volume *
100).
· To a 30 cm diameter the corresponding wastewood figure is
32-35%.
· For mangrove forest it is 9% and for teak forest 11%.
· Both
large and small sawmill lumber yield is 45% and waste is 55% (sawdust 10%, slabs
25%, log trim 17%, others 3%).
· Plywood mills yield 40% and waste 60% in
1981.
· Recent study showed plywood mill waste to be 45% (round up veneer now
used in core, resulting in a waste reduction up to 7.4%).
Silva, J.N.M. 1992. A note on Brazil's tropical rain forests under new forest management regulations. Journal of Tropical Forest Science 4(4): 355-356.
· Summarizes new forest management regulations, gazetted
in September 1991, to be enforced by IBAMA (Brazilian Institute for Environment
and Renewable Natural Resources).
· Regulations permit logging in cases where
a forest inventory demonstrates that the area is capable of sustainable timber
production.
· Regulations are designed to discipline logging operations to
minimize damage to residual commercial trees.
· Extraction activities are to
be planned and the volume extracted should be compatible with the principle of
sustained yield.
· An average logging intensity of 40 m3/ha is recommended.
· Silvicultural treatments
(e.g., climber cutting, crown liberation thinning) at 10 year intervals are
prescribed in the new regulations.
· A minimum cutting cycle of 20 years was
initially accepted, although 30 to 40 years may be more realistic in
practice.
· Timber companies are already complaining that the new regulations
will raise their cost of timber production.
· Another problem is that few
mills control the large tracts of land (>10000 ha) needed to sustainably
supply them with logs.
· There are no notes in regard to how the enforcement
will be done or will it be successful.
Silva, J.M.N., J.O.P de Carvalho, J. de C.A. Lopes, R.P. de Oliveira and L.C. de Oliveira. 1996. Growth and yield studies in the Tapajos region, central Brazilian Amazon. Commonwealth Forestry Review. 325-329.
· Study of 4 sites (7 and 13 years after logging, a
secondary forest, and a control).
· Crown exposure related well to
increment.
· Mortality rates were higher in `weed' species, except in
secondary forest where shade-tolerant species had higher mortality.
· Volume
increment was 1.6 m3/ha/year in unlogged and 4.8
m3/ha/year in logged forest.
Sim, B.L. and N. Nykvist. 1991. Impact of forest harvesting and replanting. Journal of Tropical Forest Science 3(3): 251-284.
· Study of total biomass available in a previously
selectively logged (1978) area in Sabah, Malaysia.
· Volume available (all
species with dbh > 19 cm) at site W4 146 m3/ha (145 trees/ha) and site W5 129.7 m3/ha (146 trees/ha) (based on volumes transported to
landings).
· Areas were clear felled and tractor tracks covered 24% of the
mechanically logged watershed.
Sist, P., Nolan, T., Bertault, J.-G. and Dykstra, D. 1998. Harvesting intensity versus sustainability in Indonesia. Forest Ecology and Management 108 (3): 251-260.
· In east Kalimantan, impacts of conventional logging
and reduced impact logging on forest ecosystems were compared.
· There was a
positive and significant correlation between the portion of trees damaged by
felling and the harvest intensity.
· Logging intensity ranged from 1 to 17
trees/ha (9-247 m3/ha) and averaged 9 trees/ha
(86.9 m3/ha).
· With RIL techniques, logging
damage to the residual stand could be reduced by 50% when compared to
conventional logging operations.
· Above a felling intensity of 8 trees/ha
the effectiveness of RIL in limiting damages to the residual stand was
significantly reduced, mainly due to the increasing felling damage.
· Leaving
only few potential crop trees will result in a seriously depleted residual
stand.
· With high harvest intensities, a sufficient harvesting volume will
not be reached within the cutting cycle of 35 years.
Sist, P. and Bertault, J.G. 1998. Reduced impact logging experiments: impacts of harvesting intensities and logging techniques on stand damages. In: Silvicultural research in a lowland mixed dipterocarp forest of East Kalimantan. Cirad-foret. 1998.
· This article describes the results of a reduced impact
logging study in East Kalimantan, Indonesia.
· Three options were analysed
(conventional logging, reduced impact logging with felling limit 50cm and 60cm
respectively).
· The main cause of mortality was uprooting during skidding
and felling (76.5% and 10.1% respectively).
· Stem breakage mainly occurred
during felling (8.1%) and less frequently during skidding (3.7%).
· On
average logging affected 34.4% of the area (felling 16.4%, skidding 23.6%).
·
Implementing RIL techniques did not reduce felling damage.
· In this study
logging damage was reduced from 48.8% in conventional logging to 30.5% in RIL
(felling limit 60cm).
· The different logging intensities studied when
implementing RIL techniques did not have a significant impact on the level of
logging damage.
· Only 53.7% of the volume felled were extracted from the
forest.
· Timber volume extraction must be limited to 80 m3/ha to achieve the positive effect of
environmentally sound logging methods.
Sist, P. 2000. Reduced impact logging in the tropics:
objectives, principles and impacts. International
Forestry Review 2(1): 3-10.
· Compared with conventional logging
operations (CL) the main costs of RIL arise in the planing stage.
· Barreto
et al.1998 demonstrated in the Brazilian Amazon that
implementing RIL could result in a net financial benefit of US$ 3.70 per m3.
· Africa: Logging
intensity 1-2 trees/ha or 15-20 m3/ha; generally
less than 10% of the original tree population damaged during logging. Successive
felling at a very short interval associated with poor forest inventory as
practised in Africa is not compatible with sustainable management.
· South East Asia: Logging intensity 8 trees/ha or
80-100 m3/ha; more than 50% of the original tree
population are damaged during logging.
· South
America: Logging intensity 5-6 trees/ha or 30-50 m3/ha; 25-40 % of the original tree population are
damaged during logging.
· Timber species are not uniformly distributed
throughout the forest and logging intensity can therefore vary significantly
within the same locality.
· In Malaysia, in a
forest with high climber density (n=376/ha, dbh >2cm), Appanah and Putz
(1984) observed that vine cutting prior to logging reduced the number of trees
pulled down during felling by 50%. In contrast in Sabah, in a forest with a lower climber density
(n=189/ha), Cedergen (1996) demonstrated that vine cutting had no effect in
reducing the felling damage.
· Techniques capable of significantly reducing
felling damage to stands are not yet available in the tropics. The only method
of reducing such damage that is currently available is to limit the harvesting
intensity.
· Trees damaged by logging show a much higher mortality than
undamaged ones.
· Forests harvested with RIL may recover faster (canopy
openings create favourable conditions for regeneration), so that the felling
cycle may be reduced in consequence.
· The long-term benefit of RIL may
arise mainly in the reduction of the felling cycle.
Skorupa, J.P. and J.M. Kasenene. 1984. Tropical forest
management: can rates of natural treefalls help guide us? Oryx 18(2):
96-101.
· Study of the effects of selective timber harvesting on natural
treefall rates in the Kibale Forest, Uganda.
· Results indicate that levels
of destruction typical of capital intensive mechanized timber harvesting
seriously disrupt the dynamic balance of the forest.
· The Kibale Forest has
been managed as a timber reserve with a planned felling cycle of 70 years.
· Summary of logging intensity, stand conditions after selective logging and natural tree falls:
|
K30 - control |
K14 - medium |
K15- heavy | |
|
Area, ha Logging intensity, m3/ha Years since logging Stems/ha Basal area, m2/ha Canopy cover @ 15 m, % Treefall rate per year1, % |
300 256 35.5 72 1.4 |
390 14 12 267 26.7 50 1.3 |
360 21 12 125 19.0 32 6.2 |
1Percent of all stems 9 m or more tall
· The highest rate of tree falls was in the heavy
logging intensity site.
· The link to higher tree falls is most likely a
change in forest structure that affect factors such as aerodynamic roughness,
windbreak protection by neighbouring trees, and soil cohesion.
· Conventional
mechanized logging operations that destroy up to 50% of the original forest
stand are not a sustainable method for exploiting the Kibale Forest.
· The
maximum allowable basal area reduction in selective logging was projected to be
35% to maintain natural treefalls at an acceptable level.
Sommer, A. 1976. Attempt at an assessment of the world's tropical moist forest. Unasylva 28(112-113): 5-24.
· Under the influence of a euphoric belief in its
unlimited growth, the area of tropical moist forests was seen until recently as
an almost infinite resource, covering vast expanses of our planet and just
waiting to be exploited or put to some other use.
· For the first time it
became important to attempt an appraisal of the situation at the global
level.
· At this point the difficulties began. The people involved in the
task of gathering information were suddenly handicapped by an overabundance of
data - a voluminous mass of confusing reports, scattered all over the world,
yielding very few facts.
· Various survey and inventory methods were
developed and applied, generating abundant, heterogeneous and dispersed
information. These traditional surveys were, and still are very costly and of
limited use, for selected areas.
· The global appraisal of tropical moist
forests undertaken at this time can only base its research on the material
available - a mass of incomplete data and a number of assumptions.
· The
research consists of estimates of a varying degree of reliability - their
exactitude should not be overvalued.
· Summary of the major inadequacies
characterizing the documentation are as follows:
the required information is not available in the countries concerned
not all existing information at country levels is available at FAO Headquarters
existing and available information is often obsolete, not relevant or too uncertain
available information is dispersed in various documents handled by different working units
the definitions and terms used in country appraisals vary considerably and it is very difficult to synthesise them
data from forest inventories refer often only to a selected area and are not representative of whole countries
repeated surveys for an assessment of current changes are still very rare
the same figures are repeatedly used in various reports and statements without knowledge of their origin and accuracy
· Based on general considerations in different forests
the annual growth potential can be estimated to be 1-2 m3/ha/year for Africa, 1-3 m3/ha/year for Latin America and 2-4 m3/ha/year for Asia.
· The real annual exploitation
including all the illegal activities not reflected in the statistics must
comprise far larger quantities removed.
· The direct impact of exploitation
varies widely and depends on the intensity of the fellings - slightly modified
forests by only one felling to nearly completely destroyed stands through
consecutive felling may be found.
· From 1964-73 (10-year period) an average
area of 4.6-7.2 million ha per year may have been affected, based on the
officially reported production - all the illegal fellings, in particular in
Latin America and Asia, are not reflected in these figures.
· It may be
concluded that in 1973, 0.6-1.0% of the total actual area of tropical moist
forest has been affected by the officially reported exploitation for the
officially reported roundwood production (without fuelwood). The unknown areas
under illegal felling activities have to be added to these figures.
· Areas affected through exploitation (based on roundwood production 1964-1973):
|
Roundwood production 1964 (1000 m3) |
Areas affected by exploitation (1000 ha) |
Roundwood production 1973 (1000 m3) |
Areas affected by exploitation (1000 ha) |
Increase in percentage of areas affected from 1964 | |
|
Africa |
24192 |
2400 |
31380 |
3200 |
33.3 |
|
Latin America & Caribbean |
17435 |
600-1700 |
25451 |
800-2500 |
46.0 |
|
Asia |
41875 |
700-1400 |
91815 |
1300-3000 |
119.2 |
|
Total |
83502 |
3700-5500 |
148646 |
5300-8700 |
78 |
Stoeger, N.E.1988. Waldinventur und Nutzungsplanung im Plan Piloto Forestal de Quintana Roo, Mexiko. Universitaet Goettingen. 1988. 96pp.
· For 1986 the following production costs were recorded:
furniture wood production costs 25,000 Pesos/m3,
secondary wood production costs 1,817 US$/m3.
· The costs for pre-harvest inventory were estimated at 252 US$/m3 (1-1.5% of the revenue).
· With a cutting cycle
of 15-20 years, 0.5 to 1 tree can be harvested per hectare.
· Felling and
skidding cause canopy gaps of 200 to 350 m2 per
tree felled.
Stokes, B.J., N. Higuchi, A.C. Hummel, J.V. De Freitas and J.R. Malinvoski. 1997. Harvesting in the Várzea forests of the Brazilian Amazon. In: Proceedings of the FAO/IUFRO Satellite Meeting held in conjunction with the IUFRO XX World Congress, Tampere, Finland, 4-5 August, 1995, Research on Environmentally Sound Forest Practices to Sustain Tropical Forests. Food and Agriculture Organization of the United Nations. P.47-56.
· Wet, flood areas of the Amazon.
· Average tree
diameter at stump height was 1.1 m, average height was 44.4 m and average log
volume was 11.1 m3.
· Sustainable tropical
forest management requires economically and environmentally acceptable
harvesting practices.
· 140 m3/ha of all
trees >20 cm dbh, but only 43 m3/ha for
potential commercial species.
· Estimated diameter of selected trees at least
50 cm.
· Stump height was always above 1.5 m, but could be higher depending
on the buttress.
· Gap size after felling averaged 845 m2, or twice as large as the average on the
terra-firme forest.
Sundberg, U. 1978. Implications of improved utilization of tropical forests on harvesting and transport. In: Proceedings of Conference on Improved Utilization of Tropical Forests, May 21-26, Madison, Wisconsin. USDA, For. Serv., Forest Products Lab. p.167-173.
· The cost per unit of wood is greatly influenced by
changes in harvested volumes per unit area in the range of 5-50 m3/ha, whereas above 50 m3/ha the cost differentials are much smaller.
·
The relative logging cost for logging intensities less than 20 m3/ha escalates rapidly (exponentially) with reducing
volume.
· Breakdown of inputs (costs) by main work operations in tropical forests (all values in percent):
|
Work operation |
Share of cost |
Share proportional to | |||
|
Unit basis, m3 |
Area basis, m3/ha | ||||
|
Partial |
Total |
Partial |
Total | ||
|
Surveying & mapping Felling Extraction Feeder roads Access roads Hauling Management &supervision |
10 5 15 15 15 20 20 |
20 90 30 20 40 30 40 |
2 4.5 4.5 3 6 6 8 |
80 10 70 80 60 70 60 |
8 0.5 10.5 12 9 14 12 |
|
Total |
100 |
34 |
66 | ||
· Above 100 m3/ha any
cost advantage associated with logging intensity may very well be offset by
other influences not considered in the cost calculation.
· Infrastructure in
tropical countries is often rudimentary, and its construction can cost as much
as the investment cost in a mill itself.
· Increase in utilization is
gradual, and since the next harvest is 30-60 years in the future the character
of the operations remains a "cut and get out" type or exploitation cut.
·
Increase in utilization can also be linked to other processing technologies
(e.g., pulp and paper).
· The distance from the forest resource to the mill
site bears strongly on cost and profitability.
Sundberg, U. 1983. Logging in broadleaved tropical forests: facilities and techniques to improve utilization in Indonesia, Malaysia and the Philippines. Food and Agriculture Organization of the United Nations, FO:RAS/78/010, Working Paper No. 27. 33pp.
· When extracting lower value smaller and lesser known
species a minimum logging intensity of 20-30 m3/ha is required for the operations to remain
economical.
· Road densities in moderate and hilly terrain logged by tractors
and managed on a sustained yield basis are often from 10-20 m/ha, with 15 m/ha
as a good average (= 667 m road spacing).
· This road network is comprised of
artery/main roads (20%), secondary/area roads (20-30%) and feeder roads
(50-60%).
Sundberg, U. 1987. Study on the environmental impacts of forest utilization. Food and Agriculture Organization of the United Nations, Rome, Proj. Rep. TCP/FIJ/6652. 37pp.
· Study of two logging concessions in Fiji.
· Payment
rate based on production results in excessive forest residue.
· This is
because it encourages the maximization of gross daily production without regard
to logging damage, improper bucking of logs and other poor practices.
·
Forest is mixed tropical hardwood with a stocking of around 200 m3/ha, of which around 50 m3/ha is merchantable wood above the minimum allowable
limit of 35 cm dbh.
· 40 species presently used.
· A few trees of the most
valuable species have a stem volume up to 15 m3,
however, the average for most full bole lengths delivered to the mill is around
1 m3.
· Past logging was unplanned without
any appreciable reconnaissance, and little attention paid to the proper
alignment of roads and strip roads, and environmental care was greatly
neglected.
· The financial position of the entrepreneurs is weak and there is
no incentive for investments in infrastructure (or environmental protection)
from which others might benefit after the completion of the coupes.
· Fiji
Forest Industries (FFI) has greatly improved these procedures, aiming at higher
efficiency, environmental care and also a more long-term view of the
operations.
· Area 1 the actual bulldozing of soil was minimal; trails had
revegetated rapidly and erosion almost completely ceased 1-2 years after
logging, with the exception of steep strip road sections and at the landings; if
trees are not felled into streams there is no environmental damage to the
soil.
· Surveys of logged areas indicated that soil disturbances are
moderate, but acceptable.
Supriyatno, N. 1993. Das Forstliche Wegenetz im Konzessions- und im Plantagengebiet im Vergleich am Beispiel des Forstbetriebes Pt. Inhutani II in Pulau Laut, Suedkalimantan, Indonesien. Master-Arbeit. Universitaet Goettingen. 1993. 89pp.
· This study was carried out in southern Kalimantan,
Indonesia.
· With unplanned skidding operations, skid trails and log landings
affected 10.6% of the study area.
Tabudar, E.T. 1984. The sustainability of Philippine forests. Asia Pacific Timber Industries, Oct. p.26-36.
· A report with supporting field data which shows that a
commercial forest industry can make a profit and at the same time protect the
integrity of the environment and practice sustainable operations.
· With
adequate protection the second forest can return to almost its original
form.
· From growth and yield data it is expected that the AAC will be
maintained at 40,000 m3 on a cutting cycle of 35
years.
· From the study of 33 years after logging 123.5 m3/ha was available of all species in the 60 cm and
above dbh classes.
· Growth modeling has projected the third growth volume to
be 322 m3/ha (>20 cm dbh), vs. 200 m3/ha in second growth and 261 m3/ha in original stand.
· Timber poaching and
shifting cultivation have be controlled, as well as the urge to relog areas
close to the mill before the full cutting cycle time was up.
· They have no
problem of meeting the government requirement that the second growth forest
should yield a minimum of 67 m3/ha.
Tay, J., Healey, J.R. and Price, C. 2000. Pricing Carbon Retention by means of Reduced Impact Logging: a case study from Sabah, Malaysia. University of Wales, Bangor.
· The study area is located in Sabah, Malaysia.
·
This study was carried out in dipterocarp forest with a high density of
commercial logs.
· RIL can be used to reduce adverse carbon fluxes.
·
Organisational and operational expenditures increase when implementing RIL.
·
At the second cut (60-year cutting cycle) greater yields are expected from RIL
areas than from CL areas.
· Revenue will be foregone through the lower timber
volume logged with RIL techniques.
· With RIL, 59.4 m3/ha were harvested.
· With CL, 135.2 m3/ha were harvested.
· Following logging, 50% of
the logged material is assumed to be converted to timber products.
· The mean
carbon storage over a 60-year cycle is -38.39 tonnes per logged hectare with RIL
and -94.31 per logged hectare with CL.
· Break-even carbon prices
(US$/tonne) under various circumstances:
|
Level of Analysis | ||||
|
Per representative hectare |
Per logged hectare |
Per m3 logged Scenario I |
Per m3 logged Scenario II | |
|
Mean carbon storage |
46.60 |
4.27 |
-40.50 |
-20.58 |
|
Discounted at 2% |
38.42 |
22.04 |
3.63 |
9.62 |
|
Discounted at 4% |
37.50 |
32.42 |
25.37 |
27.22 |
|
Discounted at 6% |
38.43 |
37.82 |
36.90 |
37.44 |
|
Discounted at 8% |
40.11 |
41.37 |
43.42 |
43.59 |
|
Discounted at 10% |
42.09 |
44.28 |
47.94 |
48.00 |
Where prices are negative, the RIL project is worthwhile, even without counting the benefits of increased carbon retention.
· Comparison with carbon prices derived in other ways
shows that, using the same discounting assumptions, the costs of retaining
carbon by RIL is expensive compared with most other carbon prices.
· No
generalisation should be drawn from this individual study. In other
circumstances RIL may provide a cheap carbon retention option. Particularly
because of the potential opportunity costs associated with RIL, this outcome
should not be relied upon.
ter Steege, H., R.G.A. Boot, L.C. Brouwer, J.C. Caesar, R.C. Ek, D.S. Hammond, P.P. Haripersaud, P. Van der Hout, V.G. Jetten, A.J. van Kekem, M.A Kellman, A. Khan, A.M. Polak, T.L. Pons, J. Pulles, D. Raaimakers, S.A. Rose, J.J. van der Sanden and R.J. Zagt. 1996. Ecology and Logging in a Tropical Rain Forest in Guyana: with recommendations for forest management. The Tropenbos Foundation, Wageningen, The Netherlands, Trobenbos Series 14. 123pp.
· In a lateritic area (Ekuk Compartment, Mabura Hill)
logging increased the number of gaps by 50% as compared to natural forest, the
increase in overall gap area was 400% because the gaps are larger in felling
(12.6% of area vs. 3% in natural area).
· Average logging gap size was three
times that of a natural gap.
· Less skidding activity will also lead to less
soil compaction and finally, also prove to be more cost efficient (van der Hout,
unpublished data).
· Gap size and orientation has an influence on almost all
processes (biotic and abiotic). A small gap size is to be preferred from the
point of view of nutrient loss and unwanted growth of secondary vegetation. The
actual optimum size is unknown, but a single tree fall gap is to be preferred
over multiple tree fall gaps.
· Report focuses on greenheart, which is a slow
growing species with a rotation age >60 years. Also, the absence of medium
size greenheart means that it will be a long time before a sufficient
harvestable volume is available.
· Ecological reserve exploited plot - 4 ha
logged for greenheart in 1988 with an intensity of 57 m3/ha.
· Ekuk compartment plots 15 ha logged in
1990 with an average intensity of 37 m3/ha.
·
Conclusions:
1. Nutrient levels, CEC and fertilizer efficiency are very low on sandy soils. Forestry with log intensity of exploitation appears to be the best land use option.
2. Low intensity logging of 20-25 m3/ha on sandy soils appears to have fairly little impact on the hydrological and nutrient cycle at catchment level.
3. To avoid erosion and siltation, logging should not occur in a buffer strip along creeks. Logging should also not occur on steep slopes for the same reasons, but this may depend on soil type.
4. Lack of individuals in the lower adult size classes of greenheart does not allow a second harvest after 20-25 years.
5. To compensate for low growth rate and decline in populations of commercial species relative to non-commercial species, after harvest, silvicultural treatments are necessary to ensure future commercial potential of the forest.
6. Uncontrolled skidding is a major cause of damage to the ecosystem because of:
destruction of seedlings, saplings and treelets,
soil compaction on skid trails,
leaching losses, which are largest on skid trails, and
unfavourable growth conditions due to high aluminium concentration and high acidity on trails.
7. Directional felling (herring-bone felling) should thus be used as a tool to reduce skidding impact on the forest ecosystem.
8. Gap size should be kept small, as:
changes in microclimate will be less,
establishment of most commercial climax species is likely to be best on such gaps,
surrounding forest may buffer losses in nutrients and water by root absorption, and
surrounding forest may buffer shortages in nutrients at a later stage by litter input.
9. Gaps should be evenly spaced over exploited areas as possible.
10. Some commercial species, such as Kabukalli or Futui, and many non-commercial species are favoured by larger gaps. As such, gap size will influence the future composition of the forest.
Thang, H.C. 1986. Concept and practice of selective management system in Peninsular Malaysia. Malaysian Forester 49(3): 249-260.
· In hill and dipterocarp forests shift to more
selective management.
· Under the Malaysian Selective Management System a
logging intensity of 30-40 m3/ha on a logging
cycle of 25-30 years is expected.
· Need appropriate felling limits and
leaving an adequate number of medium sized trees of marketable species for
natural ingrowth into commercial sizes.
· Need good inventory data (instead
of an arbitrary prescription).
Thang, H.C. 1987. Forest management systems for tropical high forest, with special reference to Peninsular Malaysia. Forest Ecology and Management 21(1-2): 3-20.
· Same data presented in FAO 1989b.
· Based on a
series of 100 continuous inventory sample plots of 0.4 ha each, and another 100
experimental cutting and/or silvicultural treatment plots the following
observations have been made:
dbh growth (cm/year): all marketable species 0.80; dark/light red meranti 1.05; medium-heavy marketable species 0.75; light non-meranti marketable species 0.80; non-marketable species 0.75
gross volume growth (m3/ha/year): all marketable species 2.20; all species 2.75
annual gross volume growth (%): all marketable species 2.10; all species 1.9
annual mortality: (% of numbers of marketable species) 0.9%
annual ingrowth: (% of marketable species growing-in over 30 cm dbh limit) 0.6%
· Preliminary studies have assessed felling damages to
remaining intermediate-sized trees (30 cm and above dbh) to be about 30%, with
wastage due to breakage and buckling in the range of 6.5-8% of the gross timber
volume.
· Percent damage by dbh class in SMS (>60 cm = 20%; 45-60 cm =
30%; 30-45 cm = 40%; 15-30 cm = 50%).
· Cutting cycle 25-30 years and the
cutting limit should not be below 50 and 45 cm dbh, for dipterocarp and
non-dipterocarp species, respectively.
· Should also be a minimum of 32
trees/ha left in 30-45 cm dbh class with good form of marketable species.
·
The minimum net economic cut should be in the range of 30-40 m3/ha of currently commercial and utilizable
timber.
· To account for harvesting losses such as felling breakage, defects,
high stumps, and short logs left in the forest the potential net volume
extracted is 60% of the gross volume for trees have dbh <60 cm and 70% for
trees have dbh >60 cm.
· With average annual growth rates of trees >30
cm dbh of 0.8-1.0 cm diameter and 2.0-2.5 m3/ha
in commercial gross volume, about 75% of the hill forests are capable of
producing every 30 years about 40-45 m3 net per
ha, which is about the current average logging intensity in virgin hill
forest.
· It is imperative to curtail exploitation damage to the residual
stand to not more than 30% of intermediate-sized trees (30-45 cm dbh).
Tinal, U. and J.L. Palenewen. 1978. Mechanical logging damage after selective logging in the lowland dipterocarp forest at Baloro, East Kalimantan. BIOTROP Special Publication 3: 91-96.
· In East Kalimantan mechanized equipment is used in
logging operations and this practice results in considerable damage to the
remaining stand, particularly to seedlings and saplings.
· 25 trees/ha
removed (trees removed in 4 ha area: 14 in 14-29.9 cm dbh class; 6 in 30-49.9 cm
dbh class; 19 in 50-69.9 cm dbh class; 60 in over 70 cm dbh class).
· All
residual trees with dbh >14 cm were recorded for logging damage (total 958
residual trees or 240 trees/ha)(165 dipterocarp and non-dipterocarp trees left
or 41 trees/ha).
· 50.1% of residual trees had no damage.
· 13.68% of the
trees were overgrown with climbers (can weaken or deform trees).
· 1.67% of
trees had bark damage.
· 5.22% of trees had crown damage.
· 0.73% had bark
and crown damage.
· 28.6% of trees were fallen or broken-off.
· 41
(commercial species) trees/ha (13 dipterocarp/ha) left after logging.
Tuomela, K., J. Kuusipalo, L. Vesa, K. Nuryanto, A.P.S. Sagala and G. Ådjers. 1996. Growth of dipterocarp seedlings in artificial gaps: an experiment in a logged-over rainforest in South Kalimantan, Indonesia. Forest Ecology and Management 81: 95-100.
· Regeneration capacity of logged-over forests has
decreased because most seed-bearing trees of valuable species (of best form
also) have been harvested.
· In practice, the currently applied management
and harvesting systems do not fulfil the criteria of sustainable forest
management.
· Age structure of natural rainforests is a mosaic patter:
sporadic disturbances such as treefalls are followed by emergence of young trees
in gaps thus formed.
· Dipterocarps establish an ephemeral seedling stock
characterized by stunted growth and capability of staying alive for some years
under the canopy. As soon as overhead light becomes available as a result of a
treefall or other disturbance, seedlings commence their growth and reach the
upper canopy (Whitmore 1978).
· Five different gap sizes (406, 680, 940, 945
and 1242 m2) distributed randomly through a
forest were studied.
· Height growth of Shorea fallax and Shoria parvifolia
was negatively correlated with gap opening, while with competing species there
was no correlation.
· Increasing gap size had a negative effect of height
growth of dipterocarps.
· Pioneer species colonised to a greater extent and
grew faster in larger gaps than in smaller ones - invasion of pioneer species
takes place when gap size exceeds 500 m2
(Whitmore 1975, 1978 and Brokaw 1985).
· Recommend that gap sizes smaller
than 500 m2 be used.
· In the Indonesian
Selective Logging System 10-15 trees/ha can normally be harvested from natural
forests during the logging operations (Lamprecht 1989).
Uhl, C. and R. Buschbacher. 1985. A disturbing synergism between cattle ranch burning practices and selective tree harvesting in the eastern Amazon. Biotropica 17: 265-268.
· Paragominas region of the Amazon.
· Of all the
options for economic development in the Amazon region, the selective harvest of
valuable timber species on a rotational basis is one of the most ecologically
sound.
· Selective tree harvesting, when done carefully, usually creates 3 to
6 canopy gaps/ha that are akin to natural forest tree fall disturbances.
·
Pre-existing seedlings and saplings (advance regeneration) and fast-growing
pioneer trees, usually originating from seeds buried in the soil, dominate the
regrowth.
· Because only the nutrient poor boles are removed (leaving
nutrient rich foliage, twigs, roots) and because regeneration is rapid, nutrient
loss is probably inconsequential.
· Although regeneration occurs rapidly
without further disturbance, poorly done selective tree harvesting leaves the
forest in an open, fuel-rich, fire-prone state.
· Fires set to control weeds
in adjacent degraded pastures spread readily into and through poorly logged
forests causing extensive damage, but fires reaching the edge of unexploited
forests quickly die out (penetrate only a few metres).
· The effects of
timber removal and pasture burning interact to produce more detrimental effects
than either process acting singly.
· Taken alone, selective forest cutting
(when done properly) is not a severe disturbance or cause for concern, however,
factors in the study area resulted in it being more detrimental than it should
be:
cutters are not landowners and with the use of chain saws fell all potentially harvestable trees, cutting many more than are actually harvested
bulldozers follow and sloppily drag undamaged boles with good form to spur roads, killing many saplings in the process
the end result is thousands of square kilometres of cut-up forest scarred with bulldozer tracks and laden with slash (fuel)
closed forest canopy is often reduced by 40%, vine forests (about 75% canopy cover) lose almost all their structural integrity as whole units of vine-knitted trees are toppled over
· As a result of careless logging a fire-resistant ecosystem is changed to a fire-prone ecosystem.
Uhl, C. and Viera, I.C.G. 1989. Ecological impacts of selective logging in the Brazilian Amazon: a case study from the Paragominas Region of the State of Para. Biotropica 21(1): 98-106.
· Study of logging damage caused by a modern logging
system (chain saw felling and bulldozer extraction (D4C) in the eastern
Amazonian municipality of Paragominas.
· Study in a terra firme forest with
approximately 100 tree species/ha (>=10 cm dbh), 25-35 m tall, basal area
20-30 m2/ha and above ground biomass of 250-300
t/ha.
· Typical logging operation removes 30-50 m3/ha (4-8 trees/ha or 1-2% of all tree stems >=10
cm dbh) of 30-60 species.
· In the first study
area 52 m3/ha (8 trees/ha) were extracted,
amounting to 1.7% of all trees >=10 cm dbh.
· 26% of all trees existing
prior to harvest are killed or severely damaged (12% lost their crowns, 11% were
uprooted by bulldozing and 3% suffered severe bark damage which may eventually
lead to mortality).
· 16% of the total stand basal area was harvested, while
an additional 28% of the stand basal area being destroyed or severely
damaged.
· Total forest canopy cover was reduced from 80% to 43% (46%
reduction), however, Amazonian forests normally have only 5-20% of their area in
a gapped condition at any one time.
· There was 700 m of tractor trail in the
6.8 ha area or 13 m/ha.
· In the second study
area (52 ha) 8% of total area scarred by tractor trails, however, in areas
where there was a higher concentration of desirable species >20% of the total
ground surface was scarred by tractor tracks and the canopy was totally
eliminated:
178 m/ha of tractor trails established (9250 m in 52 ha)
primary trails (all wood pulled to these and are accessible to flatbed trucks) were 12 m wide and 1670 m were built
secondary trails (spur trails off the primary trails) were 3.0 m wide and 5380 m were built
tertiary trails (used only once to pull out a single tree) were 2.2 m in width and 2180 m were built
· 30 species harvested and the logging intensity was 31
m3/ha (4.3 trees/ha)
· Removal of only 3-5
m2/ha of the basal area resulted in 34%
reduction in basal area (usually 20-30 m2/ha in
preharvested stands).
· Since stumpage is cheap in the area and forest
logging rights sell for 25-50 USD/ha depending on the quality of the timber and
proximity to roads, the mill operators have no incentive to log carefully.
·
The severe damage to mid-size trees (20-50 cm dbh) caused by careless logging,
and elevated probability of windfall and ground fires in these logged stands,
suggests relatively long rotation times of 75 to 100 years before the next crop
can be harvested. In reality, once loggers provide access to the Pará forest,
ranchers and land-hungry settlers follow close behind foreclosing the
possibility of future timber harvests.
· Problems can be combated with
careful logging practices and by reducing competition from non-valuable
species.
· Structural reforms in regulation, enforcement and forest tenure
are required to halt the reckless use of forest timber resources in the
Amazon.
Uhl, C. and J.B. Kauffman. 1990. Deforestation effects on fires susceptibility and the potential response of tree species to fire in the rainforest of the eastern Amazon. Ecology 71: 437-449.
· Study in the State of Para.
· With the
transformation of tropical landscapes to a mosaic of logged forests, cleared
fields and successional forests there is evidence that we are entering an era in
which fire is a dominant disturbance in rain forest regions.
· Overall the
fire regime in Amazonia is changing from one characterized by very infrequent
and probably low-intensity surface fires to one in which fires are relatively
frequent and of potentially high severity.
· In the study area only 50 m3/ha were harvested, while the estimated woody debris
input exceeded 150 m3/ha due to careless
logging.
· The opening up of the canopy (>50% gap area) allows the fuel to
dry during the dry season to a point that it will burn (e.g., 5-6 rainless
days).
Uhl, C., A. Verissimo, M. Mattos, Z. Brandino and I.C.G. Vieira. 1991. Social economic and ecological consequences of logging in an Amazon frontier: the case of Tailandia. Forest Ecology and Management 46(3-4): 243-273.
· 2-3 m3 of logs are
required to produce 1 m3 of sawn wood.
· An
average 2 trees/ha (16 m3/ha) were harvested in
three study areas (each about 16 ha) and trees (>10 cm dbh) damaged during
logging average 52/ha or 26/tree harvested.
· Half the damaged trees were in
gaps and the other half on roads and landings.
· 0.37 trees/ha were felled
but not extracted as a result of defects (usually heart rot).
· Loss of
canopy cover average 8.1%.
· 1.2 m3 of wood
were lost for each m3 harvested or 9.3 m3 lost for ever 8 m3
harvested.
· 16 m3/ha extracted + 3 m3/ha felled but left + 18.6 m3/ha destroyed = 37.6 m3/ha bole volume loss.
· 15 months after logging
had ceased, logging openings contained, on average, 63 seedlings of timber
species.
· An average 127 m3/ha of
harvestable wood was present in the logged stands (often then burnt by colonists
to create farms).
· On average 56 m of logging road were constructed for each
harvested tree.
· The areas cleared to establish the logging roads and log
loading zones were 5.5% (area 1), 5.3% (area 2) and 6.7% (area 3) (= average
5.8%).
· On average 126 m2 of forest were
cleared next to each cut tree to allow room for the logging truck (tractor) to
manoeuver.
· Canopy openings 8.1% of area.
Uhl, C., P. Barreto, A. Verissimo, E. Vidal, P. Amaral, A.C. Barros, C. Souza Jr., J. Johns and J. Gerwing. 1997. Natural resource management in the Brazilian Amazon: an integrated research approach. BioScience 47(3): 160-168.
· Brazil is well positioned to dominate the tropical
timber trade in the 21st century.
· In Amazonia, as elsewhere in the humid
tropics, timber extraction is done carelessly and has significant impacts on
forests, leading to severe canopy loss,, increased likelihood of fire, and vine
and grass invasion (Johnson and Cabarle 1993, Pinard et al. 1995, Uhl and
Kauffman 1990, Verissimo et al. 1992).
· Only in rare instances are forests
in the Brazilian Amazon being managed sustainably for timber production.
· A
review of forestry-related studies from the Brazilian Amazon showed that only 3%
addressed the question of forest management, a mere 1% examined logging
practices, and virtually none addressed economic and forest policy issues.
·
IMAZON project.
· Types of logging in eastern Amazonia in the 1990s:
|
Model |
Selectivity of timber harvest |
No. of species harvested |
No. of trees harvested/ha |
Economic/social system |
|
Várzea -traditional |
Highly selective low impact |
1-2 |
1-2 |
Paternalistic - local people |
|
Várzea - contemporary |
General harvest high impact |
Approximately 50 |
>10 |
Cottage industry- local families |
|
Terra firme - incipient frontier |
Highly selective low impact |
1 |
<1 |
Big business - diversified well-capitalized co. |
|
Terra firme - new frontiers |
Somewhat selective moderate impact |
5-15 |
1-3 |
Small family business - from outside region |
|
Terra firme - Old frontiers |
General harvest high impact |
100-150 |
5-10 |
Large family business - from outside region |
· Logging often changes to high impact as frontiers age
and infrastructure and access to markets improve.
· The environmental impacts
of the 5th, aggressive logging style are significant - approx. 30 trees >10
cm dbh are destroyed for each tree harvested, and canopy cover is often reduced
from 80-90% in pre-logged forests to less than 50% following logging (Uhl and
Vieira 1989, Verissimo et al. 1992).
· Logging in Para currently results in
the harvest of approximately 4000 km2 of forest
each year, producing approximately 8 million m3
of roundwood = 20 m3/ha.
· Present day terra
firme logging practices are best characterized as "forest mining", where future
entries are too soon (i.e., before the forest grows and recover to preharvesting
conditions) - take out lesser known species and smaller desirable species.
·
In addition to vines taking up growing space they also weigh down the juvenile
trees and cause bole deformities.
· Fire is another problem, with the
build-up of slash and the opening of the forest.
· The end result of terra
firme logging is often a highly degraded ecosystem that has lost much of its
forest character - in its present guise in much of eastern Amazonia logging is
really step-wise deforestation.
· Timber is under-valued and therefore used
carelessly.
· One or more trees per hectare (amounting almost to 7 m3/ha) are felled but never recovered by the skidder
operations.
· Careful planning of machine movements resulted in about 25%
reduction in the ground area affected by machine movements when compared to
unplanned logging (Johns et al. 1996).
· Vine cutting two years before
logging resulted in about 30% reduced damage to trees >10 cm in dbh (Johns et
al. 1996).
· Trained loggers were able to achieve a 3x reduction in waste
associated with felling and bucking (cuts closer to ground and reduced butt
splitting by using correct felling procedures).
· Machine operating time was
reduced by 20%.
· Girdling to kill undesirable trees after logging provided
significantly more growing space for the commercial individuals targeted for
future cuts.
· Added cost for extra inventories, mapping, vine cutting is
about $50/ha.
· The monetary losses from ineffective use of machinery and
unnecessary wood waste in unplanned operations may often be greater than the
additional costs associated with planned logging operations. Hence planned
logging may actually lead to increased profits.
· By have RIL can have a
cutting cycle of 30-40 years with a sustainable yield with each entry instead of
70-100 years.
· Sawmill yield is only 33% of each harvested log, but could be
increased to nearly 50% through simple improvements in machinery maintenance and
by training the labour force.
· By increasing logging efficiency, forest
management, and processing efficiency, companies would only require 1/3 of the
forest land that they now require for the same sawn wood output.
Uhl, C., Barreto, P., Verissimo, A., Vidal, E,. Amaral, P., Barros, A.C., Souza, C. Johns, J. and Gerwing, J. 1997. Natural resource management in the Brazilian Amazon. An integrated research approach. BioScience 47(3): 160-168.
· This study was carried out in the Pará state,
Brazil.
· One harvesting method in the floodplain forest involves the harvest
of Virola surinamensis and is highly selective, with
only 1-2 trees/ha removed.
· The logs are floated out of the forest;
therefore this harvesting method has few environmental impacts.
· An
alternative method for harvesting in the floodplain forest is high impact
logging, where 50 species are harvested with a harvesting intensity of >10
trees/ha.
· On incipient frontiers in the terra-firme forest, the harvest is
highly selective, both in harvesting intensity (< 1 tree/ha) and number of
species harvested (mahogany).
· Forest damage is low due to the highly
dispersed distribution pattern of adult mahogany trees.
· Moderate logging
is practised on new frontiers. The harvest is somewhat selective (5-15 species
harvested, 1-3 trees/ha extracted).
· Logging often changes to high impact
practices as frontiers age and infrastructure and access to markets improve.
· Reduced impact logging in the terra firme forest would include conducting
forest inventory, planning of extraction activities, and silvicultural
treatments. With RIL sustainable cutting cycles might be reduced from 70-100
years to 30-40 years.
· In typical conventional logging operations, one or
more trees per hectare (amounting to almost 7 m3/ha) are felled but never found by the skidder
operator.
· The careful planning of machine movements reduced the ground
area affected by machine movements by approximately 25% compared to conventional
logging.
· Vine cutting, conducted two years before logging, resulted in an
approximately 30% reduction in damages to trees >10cm dbh during felling
operations.
· Training loggers could reduce waste associated with felling and
bucking to 30%.
· Machine operation time could be reduced by 20% through
implementing RIL because all skid trails were preflagged, allowing machine
operators to move quickly to the felled tree.
· RIL has an added cost of US$
50 per hectare for forest inventory, vine cutting and careful planning.
·
The monetary losses from conventional operations through unnecessary wood waste
may be greater than the additional costs of implementing RIL.
· At present,
only approximately 30% of each harvested log are converted into sawn wood.
Processing efficiency could be increased to nearly 50% through simple
improvements in machinery maintenance and by training the workers.
· The
following harvesting system was proposed for Amazonian forests: a maximum of 5
trees/ha may be removed per cutting cycle; the minimum cutting cycle is 50
years; 5 m wide fire breaks must be maintained around logged stands for the
first decade after harvesting.
Vanclay, J.K. 1989. Modeling selection harvesting in tropical rain forests. Journal Tropical Forest Science 1(3): 280-294.
· Paper outlines a harvesting model which enables
estimation of selection logging yields and quantification of impact on the
residual stand.
· Important predictors include tree species and size, stand
basal area, basal area logged, logging history and topography; soil type and
site quality do not appear to influence harvesting.
· Marking rules in
Queensland allow defective trees down to a dbh of 40 cm to be removed, otherwise
it generally varies for 60-100 cm dbh depending on the species; at least 50%
canopy cover retained; directional felling to minimize damage to residual stems;
seed trees retained at a spacing of at least 40 m; allow addition trees with
outstanding form and vigour to be retained.
· Residual stem damage prediction
equations were derived from a series of nine logging damage studies from 1977 to
1980; one of the major variables is the amount (volume or basal area) logged.
The damage data comprised slope, relative basal area logged, soil type, logging
history, species, dbh and damage which was zero if the tree survived and one if
the tree was destroyed.
· Summary of logging damage studies:
|
Number of trees |
% of original stand | |
|
Base stand information - desirable trees marked for retention - merchantable stems not marked for removal - unmerchantable stem - stem marked for removal, felled & removed - stem marked for removal, felled & left as unmerchantable Total stems |
115 2145 355 424 36 3075 |
3.7% 69.8% 11.5% 13.8% 1.2% 100.0% |
|
Damage to bark, wood and crown information - destroyed (dead or will die) - other (will probably survive) Total |
308 353 661 |
10.0% 11.5% 21.5% |
· In the model logging history has an impact of volume yield (less volume available), but 38 years after logging, treemarking in a previously logged stand reached the same selection intensity as in a virgin stand.
Verissimo, A., P. Barreto, M. Mattos, R. Tarifa and C.
Uhl. 1992. Logging impacts and prospects for sustainable forest management in an
old Amazonian frontier: the case of Paragominas. Forest Ecology and Management
55(1-4): 169-199.
· Of the 238 sawmills present in the study region in late
1989, 79% were installed during the 1980s, with average production for a one
band saw mill of 4300 m3/year.
· Lumber yield
is 47 % or 2.13 m3 of roundwood produces 1 m3 of sawnwood.
· 63% were vertically integrated
with both logging and sawmilling operations.
· Average for 3 sites of 6
trees/ha harvested with a volume yield of 38 m3/ha (range from 2.9 to 9.3 trees/ha and volume 18 to
62 m3/ha).
· Typical extraction rates for the
area ranges from 20 to 50 m3/ha.
· 27 trees
>= 10 cm dbh are severely damaged for each tree harvested (= 150
trees/ha).
· 48 uprooted, 41% broken stems, 11% severe bark damage.
· Tree
damage was not in direct proportion to volume extracted (e.g., harvesting 18
m3 damaged 5 m2
of basal area in area 1, but in area 3 where more than 3 times more volume
harvested, basal area damaged increased by 50%).
· Opening about 40 m (218
m2 of scraped ground surface per harvested tree)
of logging road and 663 m2 of canopy opening per
tree harvested.
· Natural tree falls in the region open gaps from 150 to 300
m3.
· The biggest impediment to forest
management in the eastern Amazon is the undervaluing of the timber resource
(stumpage rights sold at 50-150 USD/ha).
· With careful extraction and
management procedures, harvests could be accomplished on a 30 to 40-year-cycle
and forest integrity could be maintained.· Early 70s loggers harvested only a
few high-value species and forest impacts were small.
· 20 years later more
than 100 tree species are harvested.
· Canopy coverage decreased for 82% in
control to 40-47% in logging areas (mean 45%).
· Annual dbh growth increments
of 0.8 cm/year (managed vine cutting and thinning treatments) and 0.3 cm/year
(unmanaged) reveal that the difference in accumulated bole volume between
managed and unmanaged stands, considering just commercial species >= 30 cm
dbh, will be 22 m3/ha after 35 years.
·
Pre-extraction survey and vine cutting can reduce damage by up to 50%.
·
Management cost would be about 5 USD/m3
extracted, but loggers only pay stumpage of 1-3 USD/m3 extracted.
Verissimo, A., P. Barreto, R. Tarifa and C. Uhl. 1995. Extraction of a high-value natural resource in Amazonia: the case of mahogany. Forest Ecology and Management 72(1): 39-60.
· Typical one band saw mill will on average produce 4500
m3/year of sawnwood mahogany from 9900 m3 of roundwood (45.5% yield).
· An average of 5
m3/ha (= 1 tree/ha) of mahogany removed.
·
Future mahogany cuts are in doubt because only 0.25 mahogany trees/ha of at
least 30 cm dbh found on recently logged sites and no trees between 10-30 cm
dbh. Mahogany seedlings were also rare.
· Logging damage is great - 31 trees
>10 cm dbh were severely damaged for each mahogany tree harvested; approx.
1100 m2 of forest ground was scraped clean or
trampled for each mahogany tree removed.
· After logging there is a growing
trend to convert forests to cattle pasture, in part perhaps, because the
prospects for future mahogany harvests do not appear to be good.
· The other
trees left after logging amounted to 31.3 m3/ha
of wood >30 cm dbh in the sawable category (only 0.3 m3/ha of mahogany though), 13.1 m3/ha in the potential use category, and 51.3 m3/ha without wood-related uses (these are lower than
further to the north in Para State).
· Need to encourage regeneration of
mahogany through adopting measures to increase natural regeneration (at its
success), plant mahogany in logged areas, and establish plantations of mahogany
in open areas.
· The logging cycle for mahogany may be as long as 80-100
years (when relying on natural regeneration).
Vidal, E., Johns, J. Gerwing, J.J., Barreto, P. and Uhl, C. 1997. Vine management for reduced impact logging in eastern Amazonia. Forest Ecology and Management 98(2): 105-114.
· A study on vine management was undertaken in a 210 ha
forest stand in eastern Amazon, Brazil.
· Objectives were to determine vine
species composition, stem densities, and the abilities of different vine species
to resprout following cutting.
· The degree of tree canopy connectedness due
to vines and the amount of damage associated with felling trees with intercrown
vine connections as well as the costs of vine cutting as a forest management
tool were assessed.
· Although vine cutting prior to logging can reduce
logging damage, it costs approximately US$ 16 per hectare. This is equivalent to
8% of the profits of a typical logging-only operation.
· Reductions of the
cost of vine cutting could come with the development of species-specific cutting
prescriptions that would reduce the total number of vine stems cut by focusing
cutting efforts on aggressive species likely to cause silvicultural
problems.
Virtucio, F.D. and M.G. Torres. 1978. Status of management and utilization of forest resources in the Philippines. The Malaysian Forester 41(2): 149-166.
· Average volume in dipterocarp forests ranges from
100-200 m3/ha (does not give to which minimum
dbh class or species groups).
· Gives AAC equations for the various forest
types under different management strategies.
· Reference to 3000 active
growth plots established in various logged-over dipterocarp forests for the
prediction of their growth and yield.
· Poor utilization of the hardwood
forest.
· Of over 3000 tree species in the dipterocarp forest, only less than
100 are commercially utilized.
· Present practice of forest utilization leave
voluminous waste and residue in the forest; for every 100 m3 removed from the forest, 50 m3 of logging waste and residues are generated.
de Vletter, J. and Mussong, M. 1995. Natural Forest Management Project: Ein Ansatz zur nachhaltigen Bewirtschaftung von kommunalen tropischen Regenwaeldern in Fidschi. Forstarchiv 66: 95-100.
· The purpose of this study was to test the
implementation of a silvicultural model for the sustainable management of
communally owned tropical rainforest on the Fiji islands.
· The harvesting
intensity for reduced impact logging was 38.7% of the initial volume. With
conventional logging 81.6% of the volume were harvested.
· It was found that
the local forest owners were capable of applying the prescribed management and
harvesting activities. The selection of trees to be harvested was mainly based
on silvicultural and ecological criteria but also included aspects of timber
recovery and economics.
Wagner, M.R. and J.R. Cobbinah. 1993. Deforestation and sustainability in Ghana. Journal of Forestry 91(6): 35-39.
· Nearly 93% of all forest land in West Africa (Benin,
Ghana, Guinea, Guinea Bissau, Cote d'Ivoire, Liberia, Nigeria, Sierra Leone, and
Togo) has sustained some timber harvesting.
· In Ghana soon some species will
no longer exist in sufficient numbers to be used for timbers.
· Most of the
commercial species respond well to low intensity harvesting (Hawthorne
1989).
· Disturbance is a natural part of the tropical forest, as it is for
any forest ecosystem.
· As long as harvesting mimics the natural disturbance
regimes, the tropical forests of Ghana can be sustained while being
harvested.
· Greater disturbance favours pioneer species.
· Felling limit
is 70 cm dbh.
· Growth 3-6 m3/ha/year.
·
Logging damage to the residual stand and unused forest residues may not be fully
accounted for in the allowable cut estimates. Ghana's practice of setting
allowable cuts considerably below the annual growth is prudent.
· While
tropical forest growth is sustainable, it will likely occur on a different set
of species than those presently being harvested.
· Longer felling cycles will
reduce the degree of disturbance and lengthen the recovery period.
· The
felling cycle in Ghana was recently extended from 25 to 40 years.
· Logging
methods should be revised to reduce the amount of understory disturbance.
·
It would be appropriate to leave residual "overmature" trees in stands as seed
sources and to preserve unique habitats.
· Harvesting secondary species is
often encourage - however, this could lead to greater disturbance at each forest
entry, with dramatic effects on species composition.
Watanabe, S. 1992. Percentage of felling in the natural forest and damage caused by felling operations - a case of natural forest in Lokkaido, Japan. In: Beyond the guidelines - an action program for sustainable management of tropical forests. International Tropical Timber Organization, Technical Series No. 7. P.146.
· Commercial scale operation of 20,000 ha of forests
(goal to produce a multi-storied natural forest that supplies high-quality
timber).
· Found that it is difficult to keep the stand composition intact
with selection cutting of at least 30% of the stand or more.
· When the
cutting percentage reaches 65% or more, the stand composition is destroyed.
·
Consequently, when a high percentage cutting is performed continuously, the
forests are gradually degraded.
· Based on the above a cutting percentage
(basal area assumed) of 13-17% is used.
· Has been shown that, if the natural
forest is managed at a stock level of 70-80% of the climax and a low percentage
of cutting (13-17%) is carried out in a short cycle (8-10 years), the total
harvest volume can be increased without losing the productivity and health of
the forest.
Webb, E.L. 1997. Canopy removal and residual stand damage during controlled selective logging in lowland swamp forest of northeast Costa Rica. Forest Ecology and Management 95: 117-129.
· This study was conducted in the Atlantic lowlands of
northeast Costa Rica, in timber concessions of poorly drained swamp forest.
·
This study examined the effects of a controlled selective logging operation on
forest structure.
· Harvesting was limited to trees of at least 70cm dbh,
10cm above the legal limit in Costa Rica.
· Extraction intensity averaged
6.3 trees/ha for 28ha and 45.8 m3/ha for a 7 ha
sub-sample.
· Felling, immediate residual mortality and skid trail
construction reduced the basal area by 18.3%.
· Canopy cover averaged 91.4%
in undisturbed plots and 73.4% in logged forest. The relationship between
extraction intensity and post-logging canopy cover was linear.
· Skid trails
covered 4% of the land surface. This number is slightly lower than in comparable
studies, probably because much of the area surrounding the forest was pasture,
so tree boles were skidded to landing outside the forest.
· Logging
increased the median gap size from 46.6 m2 to
83.5 m2. Prior to logging 94% of the gap
frequency and 60% of the total gap area was contained in gaps of less than 250
m2. After logging, gaps with an area over 500
m2 comprised only 17% of the gap frequency, but
78% of the total gap area.
· 17.6% of the residual stand was killed or
damaged during logging (12.4% damaged, 5.2% killed).
· Severe damage (trunk
snap or uprooting) usually did not occur to trees >50cm dbh
· Moderate
damage types (canopy damage, bark removal) were relatively more frequent in size
classes of >40cm dbh.
· When damage caused by the skid trail stabilisation
(corduroy skid trails) is not counted, residual damage estimates decrease to
about 12%.
· The absolute level of residual damage was very low compared to
other tropical logging operations.
· Logging gaps with a low commercial
value can comprise a substantial proportion of an improperly managed forest.
· The relative level of damage incurred during controlled selective logging
did not appear to deviate substantially from uncontrolled logging operations.
Weidelt, H-J. 1996. Sustainable management of dipterocarp forests - opportunities and constraints. In: A. Schulte and D. Schöne (eds.). Dipterocarp Forest Ecosystems: Towards Sustainable Management. World Scientific Publishing Co. Pte. Ltd., Singapore. p.249-273.
· Volume increment, without deducting mortality, on an
area of primary forest may range from 1- 5 m3/ha/year.
· The absolute minimum logging cycle in
dipterocarps is 35-40 years.
· The minimum felling diameter should be 50 cm,
since dipterocarps generally reach fruiting age at dbh 35-40 cm.
· With
directional felling techniques on average about 200 m2/tree felled is damaged; so if 15 trees/ha are
removed 30% of the area would have felling damage.
· In addition about 30% of
the area sustains skidding damage.
· Imperative that logging damage is
minimized to both the soil and the residuals.
Weidelt, H.J. 1989. Die nachhaltige Bewirtschaftung des tropischen Feuchtwaldes- Moeglichkeiten und Grenzen. Forstarchiv 60: 100-108.
· For Eastern Kalimantan a harvesting intensity of 35 to
105 m3/ha with a 35 year cutting cycle appears
to be sustainable (equal to 1-3 m3/ha annual
harvest).
· Silvicultural treatment can result in growth rates of 10 to
15m3/ha.
· Studies on the Philippines
indicate that a harvest of 50% of the basal area results in damages to 25% of
the residual stand.
White, L.J.T. 1994. The effects of commercial mechanized selective logging on a transect in lowland rainforest in the Lopé Reserve, Gabon. Journal of Tropical Ecology 10(3): 313-322.
· Selective logging typically results in the destruction
of 50% of all trees present before logging (Ewel and Conde 1976, Whitmore 1984,
Johns 1992).
· In 1988 it was estimated that 46% of Gabon's forest had been
selectively logged at least once, and each year about 2500 km2 is logged; 60% of which has not previously been
logged.
· Concession in the Lopé Reserve studied: logging intensity 1-2
trees/ha using conventional logging with chain saw felling and crawler tractor
extraction (traditional logging in Gabon).
· Only recently has logging begun
to diversify in Gabon with more species being extracted.
· Minimum legal
felling diameter 70 cm dbh for commercial exploitation.
· For trees having a
dbh >=70 cm (sample area 11.25 ha):
of the 175 trees (dbh >=70 cm) 30 trees died during logging and one died a year later, having a total basal area of 27.6 m2 (17.7% of stems and 20.6% of basal area)(26 felled and 5 killed during operations)
26 trees were felled, of which 23 were extracted (2 trees/ha extracted)
of the three trees not extracted, one was hollow and the other two were missed during extraction (=7.7% of felled trees)
road construction killed two trees and three were killed by falling trees during felling
few individuals were otherwise damaged during logging: three had partial crown loss and one lost bark when hit by a felled tree
· For trees having a dbh >= 10 cm (sample area 1.25 ha):
505 trees measured and 6 lianas
basal area before logging 39.41 m2/ha (408.8 stems/ha) and after logging 34.31 m2/ha (364.8 stems/ha)
during logging 55 (10.8%) stems were lost, mostly due to incidental damage
three trees were cut and extracted (BA=3.7 m2)
over half the trees lost were killed by falling trees (n=29, BA=1.3 m2)
skidder damage killed 16 trees (BA=0.4 m2)
seven trees were killed due to skid trails and roads (BA=1.0 m2)
a further 12 trees (2.4%) sustained damaged but were still surviving after one year
· Canopy cover between 2-10 m was initially 58.2% and
was reduced to 48.2% after logging.
· Overall canopy cover was 93.4% and was
decreased to 83.2% after logging.
· 1.4% of surface area covered by a major
road, 5.0% covered by secondary extraction roads (6.4% of area bare and
compacted).
· 5.0% of surface area had skidder trails and 16.9% was covered
by crowns of fallen trees.
· 71.7% of area was not physically altered during
logging.
· Extraction rates and damage levels in other parts of central
Africa are similarly low due to the low logging intensity.
· Adjacent area
logged in 1986 roads covered 1.6% of site, skidder trails and secondary
extraction roads made up 7.5% of site, and 51.2% of canopy suffered some
disturbance.
· Adjacent area logged 10-15 years prior roads accounted for
1.8% of area and skidder and secondary extraction trails 7.2% of area.
Whitman, A.A., Brokaw, N.V.L and Hagan, J.M. 1997. Forest damage caused by selection logging of mahogany (Swietenia macrophyllo) in northern Belize. Forest Ecology and Management 92: 87-96.
· The study area was located near Hill Bank in northern
Belize.
· The stands on this site were logged 10 or more years ago and had an
intact canopy; approximately 92.3 ha were included in this study.
· Logging
affected 12.9% of the study area.
· Skid roads covered 3.8% and affected
another 6.3% and thus accounted for 78% of the disturbed area.
· Logging
gaps covered 2.28% and accounted for the remaining 22% of the disturbed
area.
· Logging of large trees did not necessarily produce larger gaps than
logging of small trees.
· At logging gaps, soil density was not significantly
different between gap, gap edge and skidding area.
· Soil was twice as
compacted on skid roads than in adjacent forest. Soil compaction was over 200%
greater on roads where more than one tree had been skidded. Overall, the soil
was significantly compacted on 3.8% of the study area.
· Overall only a
small part of the residual stand, trees, and regeneration were damaged by this
operation.
· Average number of damaged stems per logged tree:
|
Species category |
Skid road (trees damaged per tree logged) |
Treefall gap (trees damaged per tree logged) |
Total (trees damaged per tree logged) | |
|
On Road |
Next to Road | |||
|
Commercial |
6.3 |
17.0 |
1.8 |
25.1 |
|
Other |
6.3 |
13.9 |
4.1 |
24.3 |
|
Total |
12.6 |
30.9 |
5.9 |
49.4 |
· Because similar numbers of commercial and
non-commercial species were damaged, loggers did not appear to make an effort to
avoid damaging species of commercial value.
· Compared to other neotropical
studies, the area disturbed per tree harvested was nearly twice as great as was
found in other studies. This may be attributed to the low harvest intensity,
because the major proportion of the damage was associated with skid trails.
· In this study, the harvest rate for mahogany far exceeded the regeneration
and recruitment capacity of the forest.
Winkler, N. 1997. Report of a case study on
"environmentally sound forest harvesting": testing the applicability of the FAO
Model Code in the Amazon in Brazil. Food and Agriculture Organization of the
United Nations, Rome, Draft Report. 59pp.
· Forest management plan is based
on techniques developed by the INPA (Instituto Nacional de Pesquisa no Amazonas)
and the CELOS Management System (Suriname, Agriculture University of Wageningen,
Netherlands).
· The general concept of sustainable management in the project
comprises of the following measures:
selective harvesting of 65 tree species of commercial interest
selective harvesting of approximately 35-40 m3/ha (about a half of the average harvestable volume of commercial species per hectare found for the entire F2M forest area)
selective harvesting of mature trees with a dbh of >50 cm
low impact extraction operations to minimize damage to residual stands
application of silvicultural treatments in order to stimulate tree growth of commercial tree species
harvesting cycle of 25 years
monitoring system of permanent sample plots for growth and yield assessment and evaluation of damage to the remaining stand as well as for research purposes
· Terrain is fairly flat.
· Preharvest cruise to map
locations of all commercial trees >50 cm dbh, as well as potential crop trees
>20 cm dbh.
· There is a high variability in harvestable volume per
hectare in primary forest; therefore, particular interest must be paid to
reliability of data provided by a general inventory.
· The results of the
commercial inventory also underline the importance of a comprehensive preharvest
survey for each cutting unit comprising technical, topographic, economic and
ecological factors, since it is considered as the most import tool in reducing
logging waste (Panzer 1991).
· Operational cruising of the area is done two
years prior to harvesting, each cutting unit is mapped individually, showing
boundaries and all features that may influence the harvesting operations (water
courses, swampy areas or other problems sites) on a 1:2000 scale map. Also, the
locations of all potential crop trees are indicated on the map. At this time
climbers are also cut.
· All information about each harvestable tree is
recorded in the field and then fed into a computer for processing - trees are
selected based on an minimum economic threshold (i.e., min. volume required),
maturity of trees (oldest first) considering silvicultural guidelines for the
management plan, as well as actual market acceptance of certain tree
species.
· A computer generate map showing the location of potential crop
trees is evaluated by a planner, the skid trail is located to maximize
efficiency and minimize impact area.
· Spacing distance between skid trails
planned at 100 m.
· If a selected trees is found to be rotten or will cause
too much damage when felled, another crop tree is selected from close by, and
the location of the rejected tree and reasons why indication on the map.
·
All felled trees are marked on the map and numbers are attached to each log and
recorded on data sheets to ensure no timber is lost; this data is entered into
the computer and updated maps are given to the pre-concentration
crewleader.
· Bunching occurs 2-weeks after felling and is done by winching
the logs to the skid trails; some logs may be bucked due to weight and new
numbers are given to each new log and recorded.
· Skidding occurs 2-weeks
after bunching and the crewleader is given an updated map of the bunched logs at
the sides of the skid trails.
· Skid trails and landing are considered to be
permanent (i.e., used in subsequent entries into the stand).
· Work studies
showed that felling operation productivity did not decrease with the planned
changes from traditional logging (i.e., direction felling, proper felling
technique to minimize damage to residuals and the tree itself, proper bucking to
grading rules).
· Planned storage time for softwoods is 1 month and 2 months
for all other species (considered to be no risk of quality loss due to insect of
fungal attack, drying, checking).
· Traditional logging system used in the
Amazon region in Brazil can be described as insufficiently planned, haphazard
timber harvesting without any considerations concerning future crop and forest
sustainability in general. Improper felling technique, which causes safety
problems, timber loss as well as poor postharvest condition of the forest, and
inefficient extraction due to lack of information about terrain conditions, tree
location and preplanned skid trail location are further characteristics of the
traditional logging system.
· In the traditional logging the operations are
usually carried out in a chaotic way, e.g., a D6 crawler tractor or skidders go
inside the stands without any plan searching for logs. The skidder operator
drives to each log due to the lack of designated skid trails. There are
remarkable losses of utilizable volume caused by forgotten, not extracted felled
trees.
· Estimated felling production rates (time is workplace time excluding
meals):
|
Method cutting unit |
Number of trees harvested |
Average m3 per tree harvested |
Average time required per tree harvested, min. |
Productivity, m3/h |
|
Environmentally sound forest harvesting system B/G09 |
50 |
7.17 |
21.50 |
20.02 |
|
Traditional timber harvesting system B/F09 |
45 |
5.88 |
18.67 |
18.90 |
· Estimated extraction production rates (time is workplace time excluding meals):
|
Method cutting unit |
Number of observations |
Average volume per load, m3 |
Average cycle time per load, min |
Productivity, m3/h |
|
Environmentally sound forest harvesting system B/G09 - preconcentration - kidding |
75 79 |
4.86 4.72 |
9.27 4.27 |
31.44 66.37 |
|
Traditional timber harvesting system B/F09 |
43 |
4.73 |
10.35 |
27.43 |
· Estimated costs of harvesting. This is not a comparison of removal of the same volume from the study areas (from the ESFHS the volume removed was 86.7 m3, while for TTHS it was 257.8 m3):
|
Activities |
Environmentally sound forest harvesting system B/G09 |
Traditional timber harvesting system B/F09 | ||||
|
Actual |
Planned | |||||
|
Producti-vity, m3/h |
Production cost, % |
Producti-vity, m3/h |
Production cost, % |
Producti-vity, m3/h |
Production cost, % | |
|
Commercial inventory Forest road Road maintenance Felling Pre-concentration Skidding |
20.02 31.44 66.37 |
19.5 30.0 7.5 11.0 32.7 11.6 |
20.02 31.44 66.37 |
19.5 30.0 7.5 8.3 29.8 11.6 |
18.90 27.43 |
30.0 7.7 62.3 |
|
Total |
112.3 |
106.8 |
100.0 | |||
· Unless the forest is left in a condition that will
permit the attainment of a desired future condition, sustainability cannot be
assured (FAO 1996). Therefore, post-harvesting assessments are an essential
requirement of sustainable forest management since they provide feedback about
the quality of the harvesting operations.
· The tables on logging damage in
the report do not make sense - cannot understand what is being presented,
because cannot compare removing 87 m3 vs. 258
m3 from similar (2.25 ha) sized areas (38.5
m3/ha vs. 114.6 m3/ha).
· However, the conclusion is made that
severe damage to potential crop trees was about two times higher in the
traditional logging area (71.7% of PCT undamaged in RIL, while 47.6% of PCT
undamaged in traditional).
· Average gap opening 124.7 m3, while Verissimo et al.
(1992) found gap openings of 150-300 m2 for
natural tree falls.
· In the RIL the skid trails were 3.5 m wide, 1200 m in
length and covered 4200 m2 (18.7%).
·
Traditional skid trails 4.98 m wide, 2646 m in length and covered 13177 m2 (58.6%).
· Average area used for forest
infrastructure per cutting unit:
|
Environmental sound forest harvesting system B/B09 |
Tradition logging system B/F09 | |||||
|
Coverage |
Area |
Coverage |
Area | |||
|
m2 |
m/ha |
affected, % |
m2 |
m/ha |
affected, % | |
|
Roads |
625 |
12.5 |
0.63 |
625 |
12.5 |
0.63 |
|
Skid trails - primary - secondary |
3500 |
100.0 |
3.50 |
13177 |
264.6 |
13.18 |
|
Landing |
400 |
0.40 |
625 |
0.63 | ||
|
Total |
4525 |
4.53 |
14.4 | |||
· In the study there were no trees lost since in both
cases the logs were marked and numbered.
· There was a difference in felling
and bucking losses (RIL = 3.9% and Traditional=8.5% of utilizable stem
volume).
Wippel. B., Grulke, M., Becker, M. and Huss, J. 1997.
Aussichten der Bewirtschaftung degradierter subtropischer Naturwaelder-
Ergebnisse waldbaulicher und sozio-oekonomischer Forschung in Paraguay. Forstarchiv 68: 251-256.
· Expenditures and
return on initial investments, Eastern Paraguay case study:
|
Expenditures (US$/ha) |
Return (US$/ha) | |
|
Large scale planning |
0.96 |
|
|
Construction of skid trails |
140.77 |
|
|
Designation of trees for harvest |
19.28 |
|
|
Stand tending and harvesting activities |
436.29 |
|
|
Stand regeneration |
17.83 |
|
|
Log yard, log sales |
53.99 |
532.71 |
|
Subtotal |
669.14 |
532.71 |
|
Total |
136.43 |
· Even without consideration of interest rates,
depreciation and overhead administrative costs the initial treatment of degraded
forests produces a deficit of US$ 136/ha.
· When forests are clear-felled
only 10% of the timber volume is used as commercial timber or fuelwood (Bozzano
and Weik, 1992).
Woods, P. 1989. Effects of logging, drought and fire on
structure and composition of tropical forests in Sabah, Malaysia. Biotropica
21(4): 290-298.
· Increase in fires is due to forests becoming more prone
to fire after disturbance by logging, which result in an accumulation of logging
debris and opening up of the canopy.
· Of the 1 million ha burnt in Sabah in
1983, 85% had been logged over.
· Of the estimated 3.5 million ha of tropical
forest burnt in Kalimantan, 77% had been logged over.
· In addition to more
fires, tree mortality in burned logged over forest is higher than in unlogged
forest (38-94% vs. 19-71%).
· Canopy loss is more severe in logged over areas
and the ground cover was dominated by grasses or woody creepers, where in
unlogged areas canopy loss was less severe and there was a low density of
grasses.
· Logging mortality (includes trees extracted) and fire/drought
mortality in the study plots by diameter classes (standard deviations in
brackets):
|
DBH class, cm |
Initial density, stems/ha |
Logging mortality, % |
Fire/drought mortality, % |
|
Burnt plots (n=5) 10-20 20-30 30-40 40-50 50-60 60+ |
252 (27) 102 (18) 45 (11) 29 (9) 20 (5) 35 (7) |
30 (9) 21 (6) 12 (10) 8 (6) 10 (7) 31 (13) |
72 (9) 55 (13) 53 (13) 49 (18) 49 (19) 38 (10) |
|
Unburned plots (n=2) 10-20 20-30 30-40 40-50 50-60 60+ |
264 (70) 102 (4) 34 (1) 22 (1) 16 (1) 42 (6) |
25 (7) 19 (2) 22 (1) 20 (9) 6 (1) 32 (5) |
24 (6) 17 (1) 20 (3) 28 (10) 12 (9) 25 (12) |
Wyatt-Smith, J. and E.C. Foenander. 1962. Damage to regeneration as a result of logging. Malaysian Forester 25(1): 40-44.
· Area damaged by logging: roads and compartment
boundary 9%, area covered by crowns 28%, area covered by boles 2%, = total
39%.
· Logged in 1959.
Wyatt-Smith, J. 1988. Letter to the Editor. Forest Ecology and Management 24(3): 219-223.
· Based on visits in 1987 to several SMS sites, as
currently practiced, he does not hold out much hope of success in respect of
sustained commercial volume production, except where Dryobalanops aromatica
(kapur) predominates.
· Growth numbers used by Thang (1987) are based on
minimal data (from 1978) which have been extrapolated from the eastern coast
States and applied to the West Coast states which have a different climate and
forest composition.
· Appears to be a lack of adequate silvical and
ecological knowledge, management control, and long-term consideration of the
future composition and rate of volume production of hill forest.
· Doubts
that the 30-year SMS cycle will be achieved in practice, and states a case where
one company has already reduced it to 25 years.
· Observations indicate that
an economic cut of the best commercial species equitable to the logger appeared
to carry the greatest weight in practice rather than ensuring sustained yield
management of the valuable species.
· Logging damage and undue selection of
logs extracted (in 1987) still appeared excessive.
· Quite clear that the
operations in the concessions visited were not sustainable.
· An already
built in 30% damage factor to intermediate-size trees at each cutting is
unacceptably high, although unfortunately probably realistic.
· The SMS by
design may yield a second cut of comparable volume to the first cut, however, it
will contain a proportion of less-desirable commercial species (current
standards). The major problem will be in the volume available from the third and
subsequent cuts.
Yeom, F.B.C. 1984. Lesser-known tropical wood species: how bright is their future? Unasylva 36: 3-16.
· Domestic markets are less discriminating.
·
Problems with increased use of LKS: difficulty in identification/inadequate data
on physical and mechanical properties/incorrect marketing in wrong
end-uses/irregular or inadequate supplies/poor grading.
· To what degree can
there be extensive increases in the harvesting of LKS before unacceptable levels
of environmental damage occur.
· At the end of 1980 it was estimated that the
total growing stock in Asia forests was 31000 million m3, of which more than 3000 million (1/10th) m3 were of commercial importance in accordance with
existing standards of utilization.
· If supplies prove scarce in one country
because of resource depletion, a ban on log exports, or higher costs, there is
always an alternative supply, at least in the short and medium term.
· When
one can pick and choose in this way, there is naturally little or no interest in
the LKS as far as the consuming countries are concerned.
· Get a problem in
smooth processing (may need to have wood stored and sorted too much if there are
more species in small quantities).
· But demand influences all - at end of
last century only one species was used in north Queensland (Australia), by 1900
10 species used, by 1930 30 species used, during and after the war years 100
species used by the sawmills and plywood industries.
· Logging intensity in
many tropical America countries 8.4 m3/ha and
African countries 13.5 m3/ha.
· Logging
intensity in Malaysia and the Philippines is extremely heavy at about 45 m3/ha in Peninsular Malaysia, 75 m3/ha in Sarawak and 90 m3/ha in both Sabah and the Philippines.
· Marn and
Jonkers (1982) - 53 m3/ha (13 trees/ha) logging
intensity in MDF in Sarawak.
· 50% of residual crop trees uprooted, broken or
injured (Marn and Jonker 1982).
· Abdulhadi et al. (1981) found 60% of the
residual stand undamaged with the extraction of 11 trees/ha.
· Studies in
Sabah have shown only 34% of the residual trees undamaged.
· 2000-3000 larger
tree species in the tropics.
· Soil damage through erosion and compaction is
another serious logging impact that could impair forest productivity.
·
Opening the canopy up too much with more intensive harvesting of LKS can result
in extreme competition from weeds, bamboo, climbers, etc., which are costly to
control.
· What is the threshold for logging? The review and discussions
above suggest that it may be of the order of 50-90 m3/ha, which is more or less the same logging
intensity in Asia.
· Viewed with this broad management perspective, the
current non-utilization of the LKS is perhaps a blessing in disguise in many
Asian countries.
· However, in Latin America and Africa, where logging
intensities are low, ecological problems arising from harvesting increased
volumes of LKS are generally of less concern.
· Need to have end-use grouping
of LKS to enable economical batch sizes for processing.
· Where logging
intensity is low, LKS are a good potential source of wood.
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· Soil disturbance 20-25% of logged area.
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· Continued work of the CELOS system.
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