Seven treatment units in three different clearcut blocks in the Golden Forest District were studied to assess overall soil disturbance levels resulting from ground-based harvesting using two methods of skidroad location. Three of the treatments were located within the Interior Cedar–Hemlock (ICH) and four within the Engelmann Spruce–Subalpine Fir (ESSF) biogeoclimatic zones.
The effects of skidroad construction on soil physical, chemical and micro-climatic properties was determined. In order to determine the impact of contour-built skidroads on survival and subsequent growth of planted seedlings, plantations were established on selected skidroad segments. Seedlings were planted in four disturbance types on the skidroad running surface and in the undisturbed (non-skidroad) soil adjacent to the skidroads. Tree growth and microclimate were monitored for three growing seasons after planting.
Total soil disturbance, which included haul roads, landings, fireguards, skidroads, skidtrails, deep gouges and deposits, ranged from 27 to 39%. Very little difference was found in overall soil disturbance levels between the pre-planned and operator choice methods of skidroad location. On the skidroad running surface, soils in the upper 20 cm of the inner track disturbance type were 40 to 60% more dense than undisturbed (non-skidroad) soils. Soils in the between track and outer track were also more dense than the undisturbed soils however the bulk density on the berm was not markedly different from the undisturbed soil. After three growing seasons, height growth and vigor of seedlings was poorest on the inner track disturbance type in all treatments. In the two blocks in the ESSF zone, average Engelmann spruce seedling height growth was less on all disturbance types, ranging from 27 to 31% less on the inner track to 3% less on the berm than in the undisturbed soil.
In the third block, in the ICH zone, height growth of Engelmann spruce followed a similar pattern; however, growth of western larch and lodgepole pine was greater on all disturbance types except for the inner track than it was in undisturbed soil (larch was 12–47% taller and pine 16–40% taller). Western larch showed the greatest height increase, followed by lodgepole pine and Engelmann spruce. Engelmann spruce had similar height growth on the neutral to slightly acid soils as on the calcareous soils.