Soil compaction caused by 450C Timber Jack wheeled skidder (Shefarood forest, northern Iran)

Abstract

In forest harvesting operations usually after using skidding machinery (skidders), traces of soil damage in the form of soil compaction and wheel and logs ruts can be seen in the forest soil. Soil bulk density, which represents soil compaction, decreases soil porosity, infiltration rate and aeration and these in turn increase runoff and water erosion in the harvested area. On the other hand, a decrease in soil aeration prevents root growth and decreases the vegetative cover. In this study the changes in soil bulk density and relative soil compaction due to a different number of wheeled skidder passes from stump to landing for two soil types (clay soil with high and low liquid limits, CH, CL) are analyzed. The results showed that the effect of skidder traffic on an increase in soil bulk density at sample locations was significant (α = 0.05). The range of soil bulk density increases in sample pits due to a different number of machinery passes was from 15.8% to 62.6% compared to the control area. The findings of this research showed that the interaction effect of skidder traffic and soil type on soil bulk density changes was not significant. Also the highest significant increase in soil bulk density occurred at the first 11 passes in skidding trails and from this number of passes onwards there was no significant difference in the soil bulk density increase in sample locations.