1041-B3

Biological and chemical amelioration effects on the localities degraded by bulldozer site preparation in the Ore Mts. - Czech Republic

Vilém V. Podrázský - Jiří Remeš - Iva Ulbrichová ¹

Abstract

Biological and chemical (fertilising, liming) amelioration are among the principal tools used to restore degraded sites. These techniques were also used on the Ore Mts. plateau on plots prepared by bulldozing. We evaluated the impact of these amelioration techniques by measuring tree species primary production and humus form restoration. Begun in 1983 - 1985, this project studied growth reaction of forest stands by measuring height and diameter increment, for 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.) during the period 1994 - 2000. The growth potential by species decreases in the following order: larch, alder, lodgepole pine, white pine, blue spruce. Beech was almost exterminated by red deer browsing and the harsh climate; pines suffered heavily from browsing and bark stripping. Holorganic horizons were measured and basic soil chemical and mechanical characteristics were determined - pH, soil adsorption complex characteristics (using Kappen's methodology), content of the humus and total nitrogen, exchangeable acidity and plant available macronutrients, granulometric composition of mineral soil horizons. Our results confirmed the relatively long-lasting effects of soil amendments, as well as the amelioration effects of alder, and the relatively inhibiting effects of larch and blue spruce.

Introduction

Large areas of forest in the Czech Republic deteriorated due to air pollution resulting from extensive industrial development. On top of the pollution-caused degradation, subsequent damage resulted from poor forestry practices including frequent bulldozing as a site preparation method. Legislative mandates created pressure for reforestation and ignored the impacts of poor technologies, resulting in approximately 10,000 ha of bulldozed plots with intense degradation (Podrázský - Ulbrichová - Moser 2001). Precise evidence of the extent of this forestry practice is missing. Although these techniques were criticised very early on (Jirgle 1984), they continued to be employed for a long time during the 70's - 80's, in some cases on into the 90's. Humus removal and nutrient cycle interruption were the main causes of the degradation effet of this treatment, intended as site preparing originally. Many research projects commenced during this time, but little data resulted, largely due to poor research administration. Only a few research plots and plantations were conserved to the present for testing of particular silvicultural and amelioration treatments in the region 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 Boleboř and to study the amelioration effects 16 years after application on the one relatively well conserved plot in the area of interest.

Methods

The Institute of Applied Ecology and Ecotechnology of the University of Agriculture in Prague, in co-operation with the Technical University of Dresden, established the research plots in 1983. The experimental plots are located on the plateau of the Ore Mts. in the altitude 850 m a.s.l., near the road between the villages Boleboř and Kalek. The site is characterised by the dominance of Cambisols and 7 ^th vegetation (spruce-beech) altitudinal zone: typical for the large areas of bulldozed plots and the localities of the mountain plateau of this region. The objective of this project was to evaluate the reforestation of sites heavily damaged by air-pollution. We especially focused on the use technical, chemical and biological amelioration treatments in site restoration (Čížek 1985, Melzer et al. 1980). The plot was prepared in 1983, tree planting and fertilisation were conducted in 1984, and the sowing of Lupinus polyphyllus occurred in 1985.

The site amelioration treatments were:

• 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), and
• post-planting sowing of Lupinus polyphyllus.

The planting technology consisted of:

• strip plough soil preparation,
• row planting with the distance between rows of 2 meters.

We evaluated four species mixes ("variants"):

1. Mixed stand (Picea pungens Engelm., Larix decidua Mill., Pinus contorta Dougl., Pinus strobus L.) at 5000 plants per ha. In addition, speckled alder (Alnus incana Moench.) was planted at a density of 1667 plants per ha on the ameliorated sites. Particular species were planted in mono-specific lines.

2. European beech (Fagus sylvatica L.) at a spacing of 2.0 x 0.6 m (8333 per ha) in mixture with speckled alder (Alnus incana Moench.) at 2500 plants per ha

3. European beech (Fagus sylvatica L.) at a spacing of 2.0 x 0.6 m (8333 per ha) in a mixture with European larch (Larix decidua Mill.), at a spacing of 2.0 x 2.0 m (2500 plants per ha). All sites are without alder.

4. Blue spruce (Picea pungens Engelm.) at a spacing of 2.0 x 1.0 m (5000 plants per ha), in mixture with speckled alder (Alnus incana Moench.) at1667 plants per ha on the ameliorated sites only.

Each species mix was replicated four times: two replications on the ameliorated blocks and other two on the control ones. 16 experimental plots were thus created, each 60 x 0.25m or 0,15 ha in size. Thirteen plots were fenced to reduce deer browse. The complete inventory (measurements of tree height and diameter at breast height) was done in 2000. Statistical analysis of the growth dynamics of each species and evaluation of the amelioration effects were done on the basis of the analysis of variance at the 95% confidence level.

Sampling of humus forms was restricted only on parts (subplots) with simple species composition. Samples of the humus form layers were taken in September 2001 using a 25x25 cm iron frame. We sampled four replications, so we might quantify the holorganic layers. Horizons were distinguished: L + F_1, and F₂ + H. The Ah mineral horizon was sampled too, but not quantitatively. The bulk samples were prepared by mixing the substrates directly in the field. We used standard analytical methods for soil analyses: dry matter amount (105 ^o C), 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 procedure.

Results

The biomass production potential (tree growth - Figure 1) confirm the 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 only on one plot. On other plots where we planted this species, there was no survival.

On the other hand, beech (Fagus sylvatica L.) was the worst of species for reforestation of the degraded plots, because it is frequently frost-damaged and almost eliminated by deer browsing. While introduced pines, particularly lodgepole pine (Pinus contorta Dougl.) showed good growth, unfortunately these species were heavily damaged by deer browse and bark stripping. Hoofed game (red deer - Cervus elaphus) is the limiting factor of the future development of the experimental plots in the Ore Mountains, as well as limiting factor for practical reforestation. Chemical amelioration showed minor, but clearly visible effects on the tree species growth, with the exception of larch.

Figure 1: Mean height (H) and diameter (D1,3) of the particular species. Heights were measured in 1994, 1999 and 2000. Diameters were measured in 2000. F - fertilized, C - control variants

Figure 2: Some species influence to the surface humus accumulation (dry mass t/ha) on the Bolebor research plots

Favourable impacts on humus form restoration were especially noticeable in the stands with larch and alder with fertilisation, both from the qualitative as well as quantitative point of view (Figure 2, Table 1). Beech was not an important component, largely due to deer browse, as in all mixtures where it occurred (Reme_ - Kratochvíl 2001). Larch demonstrated considerable litter production, whereas spruce produced the least amount of litter.

Examining fertilization and soil chemistry, the amelioration effect was clearly visible despite the passage of two decades since establishing the experiment. Larch and spruce-dominated stands had the highest decrease in pH. The lowest pH values were recorded in the blue spruce stand without fertilization, only with the basic amendment. The same trend was even more pronounced with base content (S - value) and base saturation (V - value). This was quite different from the situation observed at the surface liming application on the other research plots, in both the magnitude of the change and the longevity (Podrázský - Ulbrichová 2001, Ulbrichová - Reme_ - Podrázský 2001). The results reflect the relatively high amounts of fertilizers that were applied, their incorporation into the soil and probably the aerial liming applied over the entire study area (the last time in 2001).

Table 1: Basic pedochemical characteristics and characteristics of exchangeable acidity in stands of different tree species on the Boleboř research plot

Total humus content (Table 2) was very similar in the holorganic as well as mineral horizons of all stands with alder and fertilisation, whereas the dominance of conifers caused its decline. This observation probably reflects the slower transformation of the conifers` litter. In the case of mineral A horizon, the absence of amelioration was reflected by reduced mixing of organic and mineral soil compounds, especially in Blue spruce stands. We supposed that, due to the limited thickness of the holorganic layers, there could been some mineral particles in the samples. This species was repeatedly documented as not greatly adding to the soil function; a conclusion supported by other studies (Podrázský 2000, Reme_ - Ulbrichová - Podrázský 2002).

Plantations with alder showed increased nitrogen content in humus and soil horizons, whereas the opposite was documented in the larch and blue spruce stands, even on those sites with amelioration (Table 2). The use of liming and and the presence of alder depressed the exchangeable acidity, as evidenced by the exchangeable aluminum content (Table 1).

Table 2: Content of humus and plant available nutrients (Mehlich III) in stands of different tree species on the Boleboř research plot

Examining levels of plant-available nutrients (see Table 2), no significant differences were observed in the phosphorus and potassium contents, with the sole exception of the non-amended Blue Spruce plantation. Plant-available magnesium and calcium were affected positively, whereas the dominance of conifers resulted in a considerable decrease of these bioelements. Due to the pre-bulldozed site mechanical preparation, changes were evident at depths up to 20 cm in the mineral soil horizon. Also the humus horizons, which are usually created after the tree species plantation, had been visibly influenced by amelioration treatments. Alder had a positive effect on the upper soil layers even without the previous chemical nutrient site improvement.

Our previous survey determined that the sites were quite homogeneous (Reme_ - Podrázský 2002), which we concluded based on examination of ground vegetation, terrain type and soil morphology. Other work confirms the negative impacts of bulldozing on forest ecosystems, in general (e.g., Binkley 1986). This treatment causes increased soil erosion (Burger 1983, _ach 1995), soil structure degradation (Ballard 1988, _ach 1995) and stand nutrition degradation due to the severe disturbance of the humus layer. Soil remediation consists mainly of restoration of the humus layer (Bengtson 1981, Jirgle 1984, Vitousek - Matson 1985). In this aspect, alder was confirmed as the best "site-restoring" species, whereas larch formed a lower quality of humus. Blue spruce was not an efficient producer of humus, while other species were suppressed in their function by unfavorable abiotic as well as biotic factors. We found that chemical and biological site amelioration could be used on such plots with a high degree of success.

CONCLUSIONS

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

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

• the impact of soil amendments is observable for at least two decades, reflected in increased soil reaction, bases content, base saturation and macronutrients content.
• The effect of alder to the site is very positive. This species contributes to efficient nutrient cycling and forms a considerable amount of surface humus of favourable character.
• The restoration of the structure and quality of the humus layer represents a basic condition of forest ecosystem revitalisation.
• European larch creates considerable amount of 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 minimal positive impact upon site potential.

Our recommendations to forest managers would include the use of chemical amendments to improve productivity, and the incorporation of alder to rapidly improve the quality and quantity of the humus layer. European larch might improve the quantity, but not the quality of the humus. Soil disturbing activities, such as bulldozing, must be avoided at all costs. Control of deer browsing will accelerate the restoration of the site.

REFERENCES

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¹ Faculty of Forestry, Czech University of Agriculture Prague, Kamýcká 129, 165 21, Prague, Czech Republic. [email protected], [email protected]

Acknowledgemet: This project was supported by the grant MSM 414100009 Restoration of functioning forest ecosystems in the Krusné hory (Ore) Mts.