The effects of slash and sawdust on reducing soil compaction on skid trails

Skidding logs from stump to depot areas is the most important part of ground-based logging operations, which often leads to an increase in soil bulk density and decrease in soil porosity. In this study, woody slash and sawdust treatments with a weight of 10 kg m-2 were used to decrease soil compaction on skid trails during the trips of rubber-tired skidder Tof E655 in compartment of 29 in Bahramnia forestry plan in Gorgan, Golestan province. Soil samples were collected by steel cylinder from 0-10 and 10-20 cm soil depths after 2th, 6th, 10th and 16th skiddertrips on treated and control plots. Bulk density, porosity percentage and moisture content were measured in laboratory. Results showed the soil bulk density of 1.05, 1.12, 1.18 and 1.2 g cm-3 at the depth of 0-10 cm in bare soil after two, six, ten and sixteen trips. On trails treated by sawdust protective layer, the soil bulk densities were 0.98, 1.02, 1.07 and 1.09 g cm-3. These values for slash treatment were 0.64, 0.98, 1.05 and 1.07 g cm-3, respectively. The soil bulk densities after two, six, ten and sixteen trips were 1.31, 1.38, 1.43 and 1.45 g cm-3 at the depth of 10-20 cm in bare soil. By using sawdust these values decreased to 1.22, 1.26, 1.31 and 1.32 g cm-3, whereas the use of slash resulted in 1.18, 1.21, 1.28 and 1.31 g cm-3, respectively. The results indicated better performance of slash treatment in reducing soil compaction compared to sawdust treatment. Moreover, soil porosity at the both depths of treated plots by woody slash was more than that of other treatments and was near to forest soil porosity. Furthermore, sawdust treatments could more retain the soil moisture compared to slash treatment. Using coverage material in skid trails was concluded to reduce of destructive effects of skidder transport.