Soil compaction and conifer growth after tractor yarding at three coastal Washington locations

We measured soil density and tree growth after wet-season, ground-based yarding on fine-textured soils at three clear-cut sites. Four treatment conditions were sampled on or near four skid trails (replicates): nontilled and tilled primary skid trails, and adjacent slash-treated areas; the fourth treatment was secondary skid trails at two locations and a logged-only control at the third location. The 16 treatment plots were split into 4 subplots, each randomly assigned to a species–stock type and planted with 30 seedlings. Tree data through year 8 after planting were analyzed as a randomized block, split-plot design. Compared with nontrail areas, bulk density in the 0- to 8-cm depth on primary skid trails after logging averaged 41–52% greater. Eight years later, bulk density in the 0- to 30-cm depth of primary skid trails still exceeded that outside trails by about 20%, yet tree survival was similar except for western hemlock (Tsugaheterophylla (Raf.) Sarg.) having poorer survival on nontilled trails at on...