Scar closure and future timber value losses from thinning damage in western Oregon

This study investigated bark growth and decay development after thinning damage at two western Oregon sites, and estimated value loss with a tree growth model. All scars that remained open in western hemlock (Tsuga heterophylla) and Sitka spruce (Picea sitchensis) had advanced decay 13 years after initial wounding. Scars less than 4 inches wide closed in 8 years. Douglas-fir (Pseudotsuga menziesii) was more resistant to decay; no rot was observed in scars less than 21 years old. Advanced decay and pitch rings, however, were observed in 29-year-old scars, both open and closed. Because of these defects, future value loss increased with time after wounding and with higher stand damage levels. Fifty years after thinning, about 2 percent of the total future log value, or $189/ac. (1997$), could be lost in Douglas-fir stands with 20 percent stand damage and a 2-inch diameter deduction. This loss could be reduced to $58/ac. if stand damage were minimized to 5 percent with more careful techniques. The increase in thinning costs ($61/ac. for tractor thinning; $79/ac. for cut-to-length; $124/ac. for skyline; with a 5% increase in production time) that is incurred while trying to minimize stand damage could be justified if it reduced future value losses to crop trees.