Alexey Alexandrovich Dymov

Changes in the physical properties of podzolic soils were analysed three years after a cutting of coniferous-deciduous plantings in the territory of the middle taiga of the Komi Republic with three‒ and ten‒fold forwarder passes, as well as after leveling deep ruts formed after ten passes. The influence of different number of passes on soil density, filtration coefficient, penetration resistance is shown. An assumption about various mechanisms of soil change has been made: three forwarder passes lead to compression, ten — to compression and turbation, which was confirmed by indications of soil density and hardness. It was revealed that compression leads to an increase in density by 0.15 g×cm^‒3 and penetration resistance by 25%. Meanwhile, filtration rate did not change. Ten passes lead to turbation, which levels the possible compaction due to an introduction of forest litter into the upper mineral soil horizons. Moreover, hardness values decreased by 2‒3 times and water permeability decreased from 70 to 1 cm×day^‒1. It was revealed that leveling deep ruts causes a noticeable decrease in soil density after three years, including in comparison with the undisturbed soil. Furthermore, filtration rate increases several times. Penetration resistance is also increased. An estimation of the water retention curve approximation parameters by the van Genuchten equation made it possible to identify changes in soil of ruts compared to the a mechanically undisturbed site. A decrease in the range of mobile moisture was noted as a result of compaction after heavy equipment usage, leading to moisture stagnation in ruts.