Bulk Density Changes in Two Central Oregon Soils Following Tractor Logging and Slash Piling

Abstract

Abstract Bulk density changes were measured in two soil types within and adjacent to a 20-ha clearcut site in central Oregon. Yarding was done with rubber-tired skidders, and slash was piled with crawler tractors. Bulk density of the 0-20 cm depths was measured with a single probe nuclear gauge at randomly located sites in the clearcut and an adjacent undisturbed area with similar soils. Average bulk densities of sandy loam volcanic ash and cobbly loam soils were 35% and 23% higher, respectively, than undisturbed controls following yarding and piling. Detrimental compaction existed on 60%-66% of the harvest area when defined as either a 15% or 20% increase in bulk density. Compacted areas included skid trails, landings and land subjected to slash piling. The Proctor test and lower energy versions of this test were made on both soils to describe moisture density relationships in response to compactive forces. While the low energy curve appears to provide a good simulation of field bulk density of the cobbly loam soil, it is the moderate energy curve that provides the most reasonable estimate of soil densities after activities on the noncohesive sandy loam volcanic ash soils. West. J. Appl. For. 7(3):86-88.