Effects of skidding on forest soil infiltration in west-central Alberta

Soil compaction during forest harvesting generally reduces macropore space, which reduces infiltration and increases the potential for surface erosion and waterlogging. Hydrological effects of 3, 7 and 12 skidding cycles and their persistence were evaluated for 3 yr at 14 sites, which represented a range of soil texture and compaction conditions in the foothills and boreal forests of Alberta. Saturated hydraulic conductivity (HC) was determined using a constant head method on soil cores collected from 5- and 10-cm depths; unconfined infiltration rate of the surface soil (IR) was measured in situ with tension infiltrometers at near saturation. A significant (P < 0.05) increase in bulk density during skidding caused a significant reduction in both HC and IR after the first three cycles at eight sites where soil water potential at the time of skidding was higher than -15 kPa; the decrease at the other sites was not significant. Additional traffic, up to 12 cycles, did not cause a further significant decrease in HC or IR. The infiltration rate of soil compacted by three skidding cycles showed a recovery trend. However, in more intensively trafficked soils, compaction effects on infiltration remained significant for at least 3 yr, which was possibly attributed to heavy snowpacks preventing soil freezing at lower depths.