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Residual stand damage from cut-to-length thinning of second-growth timber in the Cascade Range of western Oregon

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Residual stand damage was measured on 25 percent of an area that had been thinned with a cut-to-length logging system. Total damage (scar area) per acre was less than in any similar study in the Pacific Northwest, although 39.8 percent of the residual trees sustained some damage. Only 0.8 percent of the trees, however, sustained major damage. Western hemlock was more susceptible to damage than Douglas-fir. Most of the damage occurred within 15 feet (4.57 m) of a trail centerline and originated within 3 feet (0.91 m) of the groundline. Early summer logging may have resulted in a higher level of damaged trees than might occur during other seasons. Future volume loss due to decay is likely to be minimal because a low percentage of scars were considered vulnerable to wood-decaying fungi.

Increased in-woods mechanization appears possible on private and public lands in Oregon. Bettinger et al. (4) suggested that the resource base in Oregon can support an increasingly mechanized industry that supplies pulpwood, sawtimber, and small-diameter material for peeling. The feasibility of increasing the use of mechanized harvesting operations, however, will depend on environmental impacts, adequate forest inventories, production costs, and markets.

Material supplied to mills from thinned stands may include more small-diameter trees (typically 3-to 10-in. diameter at breast height (DBH)). Also, thinning may improve the growth rate of the remaining stand. Young stands of Douglas-fir (Pseudotsuga menziesii) and western hemlock (Tsugo heterophylla) generally respond well to thinning, although trees in heavily thinned stands may be highly susceptible to snowbreak, windfall, and sunscald damage (6). Thinning strategies that might produce multistory stands with old-growth habitat characteristics in a relatively short time frame are currently being evaluated (20). Such strategies include commercially thinning young stands to low residual densities to allow the understory to develop.

Various types of...