Abstract
Several studies investigated soil disturbances caused on skid trails by forest logging. However, there is still a lack of knowledge about the severity and the distance of disturbances along both sides from the trails. The aims of this study were: i) to investigate the changes in physical and chemical properties of soil along the sides of skidding trails; ii) to measure the effects of soil compaction on of maple seedlings growth. Two levels of trail gradient (< 20% and >20 %), four levels of traffic frequency (3, 8, 15, and 30 passes) and four distance buffer strip zones (0.5 m intervals from 0 to 2 m in distance) on both sides of skid trail edges were analyzed. Each treatment included three replicate plots. In order to investigate the effect of compaction on seedlings emergence and growth, maple seeds were sown after logging. The results highlighted significant changes in physical and chemical properties of soil for each traffic frequency in the closest buffer strip (from 0 to 0.5 m from the skid trail edges). The largest changes in soil properties were identified at 0.5 m distance zones for a slope gradient > 20% after 3, 8, 15, and 30 skidding cycles. The highest changes were recorded on slope category >20%. The higher the soil compaction the lower the germination rate, root length, and stem height of seedlings.
Highlights
Soil compaction, defined as a reduction in total soil porosity and increase in soil bulk density, can occur naturally or be induced by human activities
The aims of this study are: (i) to determine the effect of skidding operations on extent and severity of soil compaction in the given conditions; (ii) to investigate how far from the skid trail edge there is a significant effect of skidding on soil physical and chemical parameters, taking into consideration a 2 m buffer strip at both sides of the skid trail; (iii) to investigate these changes under varying conditions of slope and traffic intensity; and (iv) to investigate the effect of compaction along skid trail sides on velvet maple (Acer velutinum Boiss) seedling emergence and growth
The maximum value of BD was reached on the skid trail with a gradient higher than 20% after 30 passes
Summary
Soil compaction, defined as a reduction in total soil porosity and increase in soil bulk density, can occur naturally or be induced by human activities. In the north mountainous forest of Iran, soil compaction caused by logging operation is a major environmental problem, especially when ground-based skidding is applied [1]. Rubber-tired skidders and crawler tractors have a negative impact on forest soils and represent one of the most important factors responsible for soil physical degradation [2,3,4,5]. Soil physical degradation leads to total soil porosity decline, mainly as a decrease in soil macroporosity (i.e., pores N 30 μm), pore connectivity reduction, and increased soil density and shear strength [6,7].
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