A wet weather ground-based yarding operation was studied to determine the impacts of skidders equipped with low ground pressure and conventional tires on soil physical and chemical properties and microclimate. To determine the effect of skidtrails on survival and subsequent growth of planted seedlings, plantations were established on segments of skidtrails in which equipment travel had been monitored and soil properties determined. Seedlings were planted on the track and between track disturbance types, as well as on adjacent undisturbed (non-skidtrail) soils of skidtrail segments on which five levels of equipment travel (<5, 10–15, 30–40, 60–70, and 100+ equipment turns) had been determined for both treatments (low ground pressure and conventional tires). An adjacent area with sharply contrasting soils was included in the study; however, skidder traffic was not monitored.
Total bulk density of the LFH layer (forest floor) and the upper 20 cm of mineral soil increased with increasing intensity of travel. However, no significant differences were found between different skidtrail segments in the low ground pressure (640) yarded treatment. In the conventional tire (740) treatment, significant differences existed between the lower and the highest level of equipment turns.
After the seventh growing season, no significant differences were found in mean height, diameter, or volume of western hemlock and Douglas-fir averaged for the track disturbance type between the 740 and 640 yarded treatments. For the between track disturbance type, no significant differences, in mean height, diameter, or volume of western hemlock were measured between treatments. However, diameter and volume of Douglas-fir were significantly lower on the between track disturbance type in the 640 treatment.
Height, diameter, and volume of western hemlock in both treatments were lowest on the 100+ turn trail segment and highest on the <5 turn segment. For Douglas-fir, similar trends occurred in the 640 treatment. However, in the 740 treatment, the 30–40 turn trail segment had the lowest height, diameter, and volume while the highest height, diameter, and volume were measured on the undisturbed soil. Seedlings planted in undisturbed soils suffered more severe moisture stress than seedlings planted in compacted track soils.