Tractor thinning productivity and costs : experience from the Willamette Young Stand Project Public Deposited
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Harvesting productivity rates and costs were determined for three silvicultural treatments used in commercial ground-based thinning of young stands to achieve timber management objectives and enhance wildlife habitat. Treatment definitions were based on residual trees per acre (tpa) after thinning. The treatments were light thin (115 residual tpa), light thin with 0.5-ac openings (92 residual tpa), and heavy thin (53 residual tpa). The three study sites were 44- to 46- yr-old stands of Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] located in the Cascade Mountains of west central Oregon. Detailed time studies were conducted on timber fallers and crawler tractors and used to develop multiple linear regression models to predict delay-free felling and skidding cycle times for each site. The independent variables common to the regression models to determine delay-free felling cycle time at all sites were diameter at breast height, number of cuts, and number of limbs cut. Only skidding distance was common to all regression models for determining delay-free skidding cycle time. Total costs for each treatment were obtained by combining felling, skidding, and moving costs for the entire operation. Felling costs ranged from $7.20/CCF to $17.73/CCF. Skidding and loading costs ranged from $15.42/CCF to $38.69/ CCF. The cost and productivity results from this study emphasize the importance for forest managers to consider factors such as volume removed and skidding distance when prescribing alternative silvicultural treatments for young Douglas-fir stands.
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