0427-B1

Site Improvement Treatments on Localities Degraded by Bulldozer Site Preparation

Vilem V. Podrazsky^[1], Jiri Remes and Iva Ulbrichova

Abstract

Biological and chemical (fertilizing, liming) amelioration are among the principal tools in the site restoration of degraded sites, and they are also used in the Ore Mountains plateau on plots prepared by bulldozing. Their effects are documented by the primary production dynamics of tree species and the restoration of humus form. The project presented was launched in 1983 to 1985. Growth reaction of the stands with the following species (Blue spruce Picea pungens Engelm., European larch Larix decidua Mill., Lodgepole pine Pinus contorta Dougl., Eastern white pine Pinus strobus L., alder Alnus incana Moench., European beech Fagus sylvatica L.) was studied in the period 1994 to 2000: the total height, the height increment and the diameter were measured. The growth potential decreases in this order: larch, alder, lodgepole pine, white pine, blue spruce. Beech was almost exterminated by the red deer grazing and the harsh climate. Pines suffered heavily from the grazing and bark stripping. Holorganic horizons were quantified and basic soil chemical and mechanical characteristics were determined: pH, soil adsorption complex characteristics by Kappen, content of the humus and total nitrogen, exchangeable acidity and plant available macronutrients. Results confirmed relatively long-lasting effects of the soil amelioration, as well as the amelioration effects of alder, and relative degradation effects of larch and especially of blue spruce.

Introduction:

Large areas of the forest stands in the Czech Republic declined because of the air pollution as a result of extensive industrial development. The degradation followed, caused by the consequent bad forestry practices including the bulldozing very often. Legislation based pressure for the reforestation and used the technologies in the economically deformed conditions resulted in the up to 10.000 ha of bulldozed plots with differently intense degradation (Podrázský - Ulbrichová - Moser 2001). Precise evidence of the extent of this treatment by the forestry practice is missing. Despite these technologies were criticised very soon (Jirgle 1984), they were used for a long time during 70ies - 80ies, in some cases also in 90ties. Relatively numerous research projects were launched in this region, but the results are still rare - the reason consists mainly in the bad research administration. Only few research plots and plantations were conserved to these days for testing of particular silvicultural as well as amelioration treatments on the territory of the Ore Mts. Their evaluation is a matter of prime importance for the future forest ecosystems management. The aim of this presentation is so to summarize briefly the growth potential of the particular tree species on experimental plot Bolebor and to study the amelioration effects 16 years after application on one relatively well conserved plot in the area of interest.

Methods

Research plot was established 1983 by the Institute of Applied Ecology and Ecotechnology of the University of Agriculture in Prague in co-operation with the Technical University of Dresden. The experimental plots are located on the plateau of the Ore Mts. in the altitude 850 m a.s.l. close to the road between the villages Bolebor and Kalek. Site is characterised by the dominance of Cambisols and 7^th vegetation (spruce-beech) altitudinal zone, it is typical for the large areas of bulldozed plots and the localities of the mountain plateau of the region of interest. This project was oriented to the reforestation of the devastated sites in air-polluted area using technical, chemical and biological amelioration treatments (Cizek 1985, Melzer et al. 1980). Plot was prepared in 1983, tree planting and fertilisation were done in 1984, sowing of the Lupinus polyphyllus in 1985.

Amelioration treatments:

- bulldozer soil preparation,
- broadcast fertilisation before soil preparation (4 t/ha CaCO₃, 0.5 t/ha K₂O+MgO, 0.2 t/ha P₂O₅),
- site preparation, fertilisation after soil preparation (1t/ha CaCO₃, 0.1 t/ha P₂O₅),
- post-planting sowing of the Lupinus polyphyllus.

Planting technology:

- strip plough soil preparation,
- line planting with the distance between lines 2 m,

Variants

1. Mixed stand (Picea pungens Engelm., Larix decidua Mill., Pinus contorta Dougl., Pinus strobus L.) in number of 5000 plants per ha. In additional, Speckled alder (Alnus incana Moench.) was planted in number of 1667 plants per ha on the ameliorated sites. Line mixture of particular species.

2. European beech (Fagus sylvatica L.) in number of 8333 plants per ha, spacing 2,0 x 0,6 m in mixture with Speckled alder (Alnus incana Moench.), that in number of 2500 plants per ha

3. European beech (Fagus sylvatica L.) in number of 8333 plants per ha, spacing 2,0 x 0,6 m in mixture with European larch (Larix decidua Mill.), that in number of 2500 plants per ha and spacing 2,0 x 2,0 m. All sites are without alder.

4. Blue spruce (Picea pungens Engelm.) in number of 5000 plants per ha, spacing 2,0 x 1,0 m in mixture with Speckled alder (Alnus incana Moench.) in number of 1667 plants per ha on the ameliorated sites only.

Each variant was replicated four times: two replications on the ameliorated blocks and other two on the control ones. 16 experimental plots were thus created, each had 60 x 0,25m = 0,15 ha. 13 plots were fenced for the game browsing elimination. The complete inventory (the measurement of tree height and diameter at breast height) was done in 2000. Statistical analysis of the growth dynamic of the particular species and evaluation of the amelioration effects were done on the basis of the analysis of variance at 95% confidence level.

Samples of the humus form layers were taken in September 2001 using the iron frame 25x25 cm in four replications, quantitatively for holorganic layers. Horizons were distinguished: L + F_1, and F₂ + H. Ah mineral horizon was sampled too, but not quantitatively. Directly in the field, the bulk samples were prepared mixing the substrates, standard analytical methods were used for soil analyses: dry matter amount (105 ^oC), pH, soil adsorption characteristics by Kappen, exchangeable acidity, total humus and nitrogen content by the combustion method and Kjeldahl method, plant available nutrients by Mehlich III precedure.

Results

The results concerning the biomass production potential (Figure 1) confirm different growth development and dynamics of the particular tree species on the experimental plots. European larch (Larix decidua Mill.) is the species with the best growth rate of all selected tree species. It reached the highest mean height and diameter at breast height on all plots. Speckled alder (Alnus incana Moench.) grew very fast too, but on one plot only. Other plots, on which this species was planted, are without alder at present.

On the other hand, beech (Fagus sylvatica L.) is the worst of species for the reforestation of the degraded plots, because it is very often damaged by frost and almost eliminated by the hoofed game. Introduced pines, namely lodgepole pine (Pinus contorta Dougl.) showed good growth, unfortunately these species are very damaged by the game. Hoofed game (red deer - Cervus elaphus) is the limiting factor of the next development of the experimental plots in the Ore Mountains, as well as limiting factor for the practical reforestation. Chemical amelioration showed minor, but clearly visible effects on the tree species growth.

Figure 1: Mean height (H) and diameter (D1,3) of particular species (cm)

Variants: first position: 1 - fertilised variants second position: 1 - mixed stand
2 - control variants 2 - E. beech + Alder
3 - E. beech + Larch
4 - Blue Spruce + Alder

Favourable effects on the humus form restoration were visible especially in the stands with alder, both from the qualitative as well as quantitative point of view (Table 1). Importance of beech in these stands was symbolic, because of its damage by big game - as in all mixtures with its occurrence. Also, the litter production by larch was considerable, spruce exhibited the least effects.

Evaluating the soil reaction, the amelioration effect was clearly visible despite two decades since experiment establishing. Blue Spruce and especially larch dominance was reflected by the pH decrease. The lowest pH values were documented in the Blue Spruce stand without fertilizing, only with basic amendment. The same trend, even more pronounced, was registered as for base content (S - value) and base saturation (V - value). This is a big difference to the situation observed at the surface liming application on the other research plots, both as for the changes size and their longevity (Podrazsky - Ulbrichova 2001, Ulbrichova - Remes - Podrazsky 2001). Registered tendencies reflect the relatively high fertilizers amounts applied, their incorporation in the soil and probably also the whole-area practice aerial liming (last time in 2001). Hydrolytical acidity (H - value) was highly suppressed by liming, it was considerably higher on the control plots and in larch stands.

Table 1: Surface humus accumulation and basic pedochemical characteristics in stands of different tree species on the Bolebor research plot

Note: AL - alder, BE - beech, SP - blue spruce, LA - larch

Total humus content (Table 2) was very similar in the holorganic horizons of all stands with alder, presence of conifers caused its lowering. This reflects the slower transformation of conifers´ litter. In the case of mineral A horizon, absence of amelioration in alder stands was reflected by lower mixing of organic and mineral soil compounds. Extreme trend was observed in the Blue Spruce without amendment - humus content was much lower also in holorganic horizons - it can be supposed, that due to the low thickness of holorganic layers there could been some mineral particles in the samples. This species was repeatedly documented as functionally value-less tree species, this conclusion is in accordance with other studies disposable (Podrazsky 2000, Remes - Ulbrichova - Podrazsky 2002).

Plantations with alder showed increased nitrogen content in humus and soil horizons, the opposite was documented in the larch stands and also in the Blue Spruce stands - even at site amelioration. Use of liming and alder activity depressed the exchangeable acidity, determined especially by the exchangeable aluminum content. Content of exchangeable hydrogen (H ex) indicated the same trends, being very low in general.

Table 2: Content of humus, nitrogen, and characteristics of exchangeable acidity in stands of different tree species on the Bolebor research plot

In the plant available nutrients content (Mehlich III method - Table 3), no significant differences vere observed as for the phosphorus and potassium contents - with the only exception of non-amended Blue Spruce plantation. Plant available magnesium and calcium were affected positively, the dominance of conifers resulted in considerable decrease of these bioelements content. Due to the site mechanical preparation (of the before bulldozed soil), changes are detected up to 20 cm of mineral soil horizon. Also the humus horizons, which were created usually after the tree species plantation, have been visibly influenced by amelioration treatments. Alder had positive effects on the upper soil layers even without the previous site improvement by chemical amelioration.

Table 3: Content of plant available nutrients (Mehlich III) in stands of different tree species on the Bolebor research plot

Site homogenity can be supposed on the basis of previous survey (Remes - Podrazsky 2002), dealing with ground vegetation, terrain type and documented by soil prospection and soil texture determination. Also the other authors confirm relatively negative impacts of bulldozing on the forest ecosystems, in general e.g. Binkley (1986). This treatment causes increased soil erosion (Burger 1983, Sach 1995), soil structure degradation (Ballard 1988, Sach 1995) and stand nutrition degradation due to the humus layer disturbance. Soil remediation consists mainly in the humus layer restoration (Bengtson 1981, Jirgle 1984, Vitousek - Matson 1985). In this aspect, alder was confirmed as the best site restoring species, larch as species forming less favourable humus form. Blue Spruce was not efficient, other species were supressed in their function by unfavorable abiotic as well as biotic factors. Chemical and biological site amelioration can be used on similar plots with high succes.

Conclusions

Growth potential, as an expression of the biological primary production, determines the function effectiveness of the particular preparatory tree species. Main restoration effect consists in the biomass production and the humus layer restoration. Larch and alder are autochthonous species with the maximum revitalization potential (larch - quantity, alder also quality of bio- and necromass). Soil amelioration plays also the role, unfavorable site conditions are more limiting.

Results confirmed favourable effects of both chemical as well as biological amelioration treatments on the soil and humus forms. They can be summarised as follows:

- Use of amelioration materials is visible at least two decades, being reflected by increased soil reaction, bases content, base saturation and macronutrients content.

- Effect of alder is very positive, this species contributes to efficient nutrient cycling, it forms considerable amount of surface humus of favourable character.

- Restoration of site corresponding humus form represents a basic condition of forest ecosystem revitalisation.

- European larch creates considerable amount of row humus of lower quality. Its high biomass production, especially in mixed stands, could be used for humus layer recovery, leaving all the formed biomass for spontaneous decay and transformation.

- Blue spruce is a site degrading species with minor function potential.

Treatments of chemical as well as of biological site amelioration can be used with advantage on plots degraded by bulldozers. Amount and type of fertilizer and tree species selected determine success of all amelioration projects.

References

Ballard, T.M., 1988. Soil degradation associated with forest site preparation. In: Degradation of Forested Land: Forest Soils at Risk. Victoria, B.C. Ministry of Forests, p. 74 - 81.

Bengtson, G.W., 1981. Nutrient conservation in forestry: a perspective. Southern Journal of Applied Forestry, 5(2): 50 - 59.

Binkley, D., 1986. Forest nutrition management. New York, J. Wiley. 289 p.

Burger, J.A., 1983. Physical impact of harvesting and site preparation on soil. In: Maintaining Forest Site Productivity. Clemson, SC, Soc. of Foresters 1983: 3 - 11.

Cizek, J., 1985. Umstrittene Fragen der Waldbautechnik in Immissionsgebieten. Proceedings ÚAEE, (4): 79-94.

Jirgle, J., 1984. Reasons for some preparatory species decline in the Ore Mts. area. In Czech. Zpravy lesnickeho vyzkumu, 26(2), 15 - 21.

Melzer, E.W.-Lucke, E. - Hertel, H. J., 1980. Technische-biologische Melioration und Baumartenmischung, Faktoren zur Leistungssteigerung zum Tharandter Meliorationsverfahren. Lesnictví, 26, Praha: 745-755.

Podrázsky, V., 2000. Influence of the forest stands species composition to the soil state. In Czech. Práce VÚLHM, (82): 115 - 124.

Podrazsky, V. - Ulbrichova, I., 2001. Evolution of the forest soils and experimental plantings on the limed immission clearcuts. In Czech. Czech University of Agriculture Prague: 111 - 122.

Podrazsky, V. - Ulbrichova, I. - Moser, W.K. 2001: Ecological impact analysis of mechanised site preparation techniques. Journal of Forest Science, 47, Special Issue: 146 - 149.

Remes, J. - Kratochvil, J., 2001. Growth dynamics of the experimental plantings in the immission area Ore Mts. In. Czech. Czech University of Agriculture Prague: 167-172.

Remes, J.- Podrazsky,V., 2002. Influence of the biological and chemical amellioration to the humus profile restoration on the bulldozer degraded site in the Ore Mts. In Czech. Czech University of Agriculture Prague: 43-52.

Remes, J. - Ulbrichova, I. - Podrazsky, V., 2002. Ecological demands and functional effects of he Blue spruce. In Czech. Lesnická práce, 81(7), 306 - 307.

Sach, F., 1995. Mechanized site preparation for reforestration in Ore Mts. and the soil erosion. In Czech. Práce VÚLHM, 80: 65 - 80.

Ulbrichova, I. - Remes, J. - Podrazsky, V., 2001. Dynamics of the forest soils state and plantings nutrition in the immission areas - influence of the surface liming. In Czech. Czech University of Agriculture Prague: 123 - 128.

Vitousek, P.M. - Matson, P.A., 1985. Intensive harvesting and site preparation decrease soil nitrogen availability in young plantation. Southern Journal of Applied Forestry, 9: 120 - 125.