Young Douglas-fir stands were commercially thinned to achieve vegetation- and wildlife-related objectives. Harvesting and forwarding production and costs were compared among three mechanized thinning treatments: light thin [(115 residual trees per acre (tpa)], light thin with 0.5-ac openings (92 residual tpa), and heavy thin (53 residual tpa). The sites were 40- to 50-yr-old stands in the Willamette National Forest in the Cascade Mountains of central western Oregon. Using multiple linear regression equations with indicator variables, we compared both harvesting and forwarding cycle times among treatments. We conducted detailed time studies on a harvester and a forwarder and used these data to develop two regression equations to predict delay-free harvest cycle times and delay-free forwarding cycle times. Delay information was gathered from both shift-level and detailed time studies. Total costs for each treatment were obtained by combining costs for harvesting, forwarding, and moving equipment in and out for the entire operation. Harvesting and forwarding costs did not differ significantly between light and heavy treatments, but were higher in the light-thin-with- openings treatment. Total thinning costs among the three treatments ranged from $28.08 to $34.62/100 ft³.
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