Han, Han-Sup; Kellogg, Loren D. 1997. Comparison of damage characteristics to young Douglas-fir stands from commercial thinning using four timber harvesting systems. In: Ball, John J.; Starnes, Lawson w., eds. Proceedings: Forest operations for sustainable forests and healthy economies; 1997 July 28-31; Rapid City, SD. [Place of publication unknown]: Council on Forest Engineering (COFE): 76-85.
Each harvesting system leaves its own type of damage to crop trees during thinning operations. Understanding theimpact of different harvesting systems helps forest managers to achieve management objectives associated with sustainabilityand quality control. Damage to residual trees from commercial thinning was characterized and compared with four common har-vesting systems in western Oregon: tractor, cut-to-length, skyline and helicopter This study was conducted in six young (30 - 50years old) Douglas-fir (Pseudotsuga menzies) stands having various residual densities. Scarring by ground-based systemswas more severe: scar sizes were bigger, and gouge and root damage was more prevalent than that caused by skyline and heli-copter systems. Crown removal and broken-top damage was more common with skyline and helicopter logging. The damagelevels varied among different thinning treatments and logging systems. The levels were heavily influenced by many compound-ing factors. In the cut-to-length system, the harvester caused more wounding to crop trees than the forwarder, but forwarderscars were larger and sustained severe gouge damages.
KEY WORDS: logging damage, commercial thinning, harvesting systems