Soil compaction after yarding of small-diameter Douglas-fir with a small tractor in southwest Oregon - Introduction

This study evaluated the effect on soil bulk density of yarding small-diameter Douglas-fir (Pseudosuga menziesii var. glauca (Beissn.) France) with a small tractor. Levels of compaction were measured before yarding and after one trip, three trips, and six trips by the tractor. Bulk densities in the surface (10 cm) and subsurface (20 cm) for three trips and six trips were higher than pretreatment (p less than or equal to 0.10); however, increases in soil bulk density were less than 7 percent and well below standards for detrimental soil compaction used by the USDA Forest Service Pacific Northwest Region. Results from this study support observations made in other compaction studies that much of the increase in bulk density from ground-based yarding operations occurs in the first few trips. Other studies, however, show a much higher increase in bulk density over undisturbed values.