Mitigating effects of slash on soil disturbance in ground-based skidding operations

Reinforcement of skid trails with slash has been shown to reduce soil disturbances, but there have not been any studies documenting the mitigating effects following traffic of harvest equipment traffic on steep mountainous skid trails. The objective of this study was to quantify potentially mitigating effects of slash cover on soil compaction and rutting on skid trails in mountainous hardwood forests. The effects of the placement of no slash (bare soil), light density slash (7.5 kg m^-2) and heavy density slash (17.5 kg m^-2) in a skid trail following one, five, and nine machine passes on both gentle slopes <20% and steep slopes >20% in a downhill skidding operation by a steel-tracked skidder were studied. Bulk density and rut depth increased following harvest equipment traffic on both slope gradients. Compared to bare soils, soil bulk density was not significantly reduced by light slash density; however, soil bulk density was significantly reduced by heavy slash up to five machine passes on steep slopes. Light and heavy slash significantly reduced rut depth in both slope classes. The study revealed a high protective role of slash, particularly on steep skid trails. However, benefits of slash to mitigate soil compaction were limited to five passes, after which the slash deteriorated and only provided benefits against rutting.