Manual methods in land preparation are used in the following cases:
- Where the topography is too steep, rugged, wet or rocky for mechanized land clearing.
- Where labour is cheap and easily available, and its use is desirable to help reduce rural unemployment.
- Where sites are fragile and could be harmed by mechanical disturbances.
- Where the soil characteristics and environmental conditions do not justify any large-scale mechanical operations for improving survival and/or growth.
- Where time is not a pressing factor.
In this planting practice, plants are simply inserted into holes or slits made by a trowel (Chapman and Allan, 1978).
- To retain the existing ground cover in order to take advantage of its ability to protect planted seedlings from frost or from exposure to extreme solar radiation.
- To reduce or avoid causing erosion on steep slopes with erodible soils.
- To eliminate the cost of pre-planting operations.
- on sites where the ground cover consists predominantly of grass species, or of low, shrubby plants.
- on old clear-felled forest lands or dry heath moors, where soil nutrients and moisture are sufficient for new plantations.
There is no need for site preparation operations including land clearing and soil cultivation before planting. The most commonly used technique is to insert the tree seedlings into holes or slits made by using simple hand tools such as a trowel or a planting spade.
Attention should be paid to the ecological suitability of the plantation site.
Nutrients and moisture must be available in order to
ensure the successful establishment of the plantation. In the case of erosion-prone soils
and steep topography, there must be adequate protective cover between planting holes on
the ground.
In the direct planting technique, repeated post-planting weeding and slashing may be necessary to keep the young plantation from being swamped by the indigenous plant cover. However, the operation should ensure that the protective effect of the indigenous ground cover is maintained.
This method consists of vegetation clearing and soil cultivation confined to narrow strips or relatively small patches on sloping lands with erodible soils in arid and semi-arid regions, cleared strips and patches are usually situated on the contour lines. The width of the cleared strips or patches varies from 1 to 1.5 metres. They should be cultivated to a good tilth before sowing or planting. The hand tools most commonly used for this technique are the mattock, heavy hoe and grubber. The mattock consists of a hoe or digging blade on one side and a pick or cutting blade on the other.
- To clear the land from competing vegetation and increase the survival and growth rate.
- To cultivate soil on patches or strips along the contour lines of slopes in order to improve moisture conditions.
- To build contour trenches or gradoni for absorbing and storing water for newly planted seedlings and young trees.
- To prevent flash floods or dry mantle floods.
- To control run-off and erosion on steep slopes where plant cover has deteriorated, and vegetation or afforestation is required.
- On sites covered with dense indigineous shrubby vegetation such as low maquis or pseudo-maquis of the Mediterranean region.
- Where the severe competition of a dense herbaceous plant cover is harmful to a new plantation.
- On dry sites where soil moisture is limited during the growing season because of pronounced summer drought.
- Where controlled burning cannot be carried out safely and effectively.
- Where land clearing and whole area cultivation is not economically feasible.
On steep sloping land, the indigenous shrubby and herbaceous vegetation should be cleared on strips or patches along contour lines before planting. Strip clearing rather than patch clearing may be preferable for sites where the shrubby vegetation is extremely dense and high, and severe competition for the new plantation is expected. The uprooted vegetation on strips situated along contour lines should be stacked along the lower edge in order to minimize the erosion hazard and to conserve water by retarding surface run-off. The soil on contour strips may be cultivated by ploughing on sites where the soil characteristics, topography and rainfall conditions permit such an operation. On rugged topography and in arid and semi-arid climatic conditions, soil cultivation is often combined with suitable soil and water conservation measures such as contour trenches or gradoni.
Post-planting weeding may be necessary in certain cases to minimize competition. Regular maintenance of the plantation during subsequent years leads to a definite improvement in growth.
Controlled burning is the oldest and cheapest pre-planting site preparation method. It involves clearing or cultivating a fire break around the area and burning a strip at least 50 metres wide into the wind, with the fire being kept under control by beaters (Chapman and Allan, 1978).
- To remove the native grass or shrubby vegetative cover. This improves the establishment of the plantation and increases the survival and growth rate by eliminating competition for moisture, nutrients and light.
- To assist and increase the turn-over of mineral nutrients bound to the vegetative cover.
- To protect the young seedlings against wildfire for at least a year.
- On land where heavy grass or rough vegetation may cause planting difficulties.
- Where the topography is not steep and the soils are not erodible.
Prescribed burning requires careful planning and is best carried out about a month before the planting of seedlings. The landowner must be sure that he has enough men and equipment to keep the fire under control.
The weather forecast should be carefully monitored beforehand and the operation should be carried out on a day which has a steady wind of not more than 10 to 15 km per hour. The ability to control the fire and prevent it spreading depends on the prevailing air temperature, humidity and fuel moisture. A fire should not be started during dry, windy or hot weather. A fire break must be cultivated around the entire area which is to be burned; natural barriers such as ponds, roads or streams can be used as part of the fireline. A wider base line opposite the downwind area should be adequately cultivated to prevent a stray gust of wind from blowing the fire out of the burned area and onto unprepared land.
If the site is large, the area should be broken up into tracts of 100 to 400 hectares. The fire lines of the tracts should be parallel to each other and at right angles to the direction of the wind on smaller sites, a fire break around the designated area is cleared, cultivated and a 50 m wide strip is initially burned into the wind, with the blaze being controlled by beaters.
Controlled burning is a proven and effective tool in site preparation for afforestation and silvicultural management of forest stands. The most important benefit of controlled burning is the elimination or minimization of competition from undesirable ground cover on plantation sites.
Burning as a site preparation method has little permanent effect on site productivity. However, it is believed to stimulate growth by increasing the availability of certain mineral nutrients bound to the plant cover burned. Attention should be paid to the adverse effects of burning on erodible soils with steep topography.
Smoke management procedures should be followed during burning operations in order to minimize pollution of the environment, including: selecting the atmospheric conditions best suited for smoke dispersion; being aware of special smoke-sensitive areas downwind from the fire such as cities, hospitals, airports, etc.
This site preparation operation entails the removal of woody vegetation from a large area using traditional hand tools. The operation and its objectives vary according to: the type of vegetation to be cleared and/or felled; the climatic characteristics of the region; and The potential use of the cleared woody vegetation.
- To remove woody vegetation including bushes and trees. This eliminates or minimizes the competition between the indigenous vegetation and the new plantation for nutrients, moisture and light.
- To combine the dual benefits of stimulating better plantation growth and obtaining income from the cleared woody cover.
- On sites where a dense cover of bush or degraded forest remnants may threaten the success of the new plantation.
- In areas where the operation is economically feasible due to the abundance of cheap labour compared to the high cost of mechanized land clearing operations.
- Where the financial cost of the land clearing operation may be offset by the commercial value of the cleared vegetation, for example, as firewood, charcoal, timber, pulpwood, poles or posts.
- Where the site may have been previously logged and the usable and commercially-viable material has already been removed, leaving only stems, weeds, coppice sprouts, and understory forest.
- In tropical regions where underbrush and small trees are left behind after selective logging or clear felling and the competition needs to be eliminated to encourage better growth of the new plantation.
- Where soil erosion or compaction might be caused by the use of heavy machinery.
On previously logged forest lands, where felling debris, stems, regrowths and weeds are left behind, a crew of workers or loggers using hand tools, should clear the vegetation for broadcast burning. Alternatively, they should pile it in heaps or rows where it can be burned off or left to rot.
Work crews can be divided into two groups, one to clear all the ground vegetation and stems up to 7.5 cm in diameter, the other to fell all the remaining stems and trim the branches from the larger felled trees.
On rain forest lands, the cut-over areas should be burned a few weeks later during a dry period. The heavier logs, however, should be conserved. The brushing and felling work alone requires up to 50 man-days per hectare (Chapman and Allan, 1978).
In tropical high forests, underbrush and small trees should be cleared following selective cutting, by a crew of workers using machetes or similar hand tools. Larger trees should be felled with power saws. In such areas, broadcast burning should be carried out in the dry season when the manual clearing operation is completed. The felling and burning operation requires an average of 86 man-days per hectare (Chapman and Allan, 1978).
Stumping to remove roots may be required for sites where subsequent cultivation is planned. This operation involves excavation, root cutting and felling, using conventional hand tools such as spades, hoes, mattocks and axes. In some cases, this operation may include digging deeply in a wide area around a standing tree.
This method is reliable and effective on sites where a mechanized operation involving heavy machinery may create soil compaction.
Care should be taken on sites with steep slopes and erodible soils where stumping may require large excavations and could cause soil disturbance and/or landslides.
This technique is used in tropical and Mediterranean climates in which degraded forest or bush-covered land is cleared in strips. The width of these strips depends upon the topography, existing vegetation and soil characteristics. In certain cases in the tropics, the land is cleared or the forest trees may be selectively removed for enrichment by lineplanting. This latter practice is the establishment of a tree crop to be closed at rotation age, in lines, spaced at intervals equal to or slightly greater than the estimated final-crop crown diameter (Chapman and Allan, 1978 quoted from H.C. Dawkins, 1978, and A.F. Lamb, 1969).
- To clear the woody plant cover (whether bushy vegetation or forest) on strips in order to convert the area into a complete man-made forest.
- To remove woody plants and forest trees for an enrichment planting. This is a practice which improves certain desirable timber species by leaving them in the natural forest.
- To minimize competition for nutrients, moisture and light between the planted seedlings and the-existing vegetation.
- To improve the growth of the new plantation, and minimize > I environmental hazards at minimum cost.
- In tropical regions where enrichment planting is planned. The following criteria for successful enrichment line planting, however, should be taken into consideration (Chapman and Allan, 1978):
(i) There must be little or no demand for thinnings in the area concerned.
(ii) The species planted must grow at least 1.5 m each year and be naturally straight and self-prunning, i.e. generally of the colonizing or gap-filling, light-demanding type.
(iii) There must be no upper canopy; only cleared felled, clearpoisoned, or low secondary forest is suitable.
(iv) Regrowth between the planted lines must be non-inflammable, or fire control measures must be put into practice.
(v) Grazing animals must be absent or scarce and cause negligible damage to the planted trees.
- In temperate or/and Mediterranean climates where ground cover consists of either high or low maquis vegetation and a conversion planting on strips is planned.
- On arid or semi-arid sites where a thick cover of bushy vegetation presents severe competition for strip line planting.
- Where rugged topography and erosion-prone soils call for contour planting and appropriate soil and water conservation measures.
If there are no suitable roads or paths, a cleared base line should be established at right angles to the planned planting line after taking into account the topography and ecological circumstances. The planting lines should then be blazed out at right angles to the cleared base line by a brushing crew, with the aid of proper optical instruments or a compass. The existing vegetation on the blazed lines should later be cleared on strips by cutting and felling, either with or without stumping. The width of the strips and the need for stumping are determined by the environmental conditions, existing vegetation, available labour, cost and time.
The cleared vegetation and resulting debris should be piled along the lower edge of the strip on sloping land. It is then either burned or left to rot. The soils on the cleared strips should be then cultivated and prepared for planting using hand tools such as hoes or spades.
In dry climates, clearing of the existing bush vegetation on strips (usually maquis) helps protect and stabilize the sloped land by accelerating growth. This is due to the elimination of competition for the young trees concerned. On steeply sloping ground, strip clearing has proved beneficial in cases where total clearing and subsequent full cultivation are avoided because of environmental concerns.
