Abstract
Demand for higher value-added wood products stimulates research for new, mainly mechanized, thinning operations in order to increase productivity and reduce production costs. In this context, the aim of this study was to evaluate the impact of distance between strip roads on forwarder productivity and costs of thinning operations in Pinus taeda stands. The study was carried out in 10-year-old Pinus taeda stands located in Parana State, Brazil. Two thinning methods were evaluated: (1) TH5: systematic harvest in every fifth tree row and selective harvest in adjacent rows; and (2) TH7: systematic harvest in every seventh tree row and selective harvest in adjacent rows. Working cycle times, productivity and costs were determined through a time-motion study of the forwarder. The additional variables evaluated were wood assortments (industrial wood and energy wood) and extraction distances (50, 100, 150 and 200 m), and mean values were compared between thinning methods using t tests for independent samples (α=0.05). Loading and unloading elements consumed the most time in the working cycle, with lower participation time in TH7 due to greater availability of logs along the strip roads (higher pile volumes), influencing total cycle time up to the mean distance of 150 m for both assortments. TH7 consequently showed 6% higher productivity, its energy yield was 5.3% lower and its production cost was 3.0% lower.
Highlights
Thinning is a well-recognized treatment in order to improve increment and quality of the remaining trees (Lamprecht 1990, Campos and Leite 2017)
Thinning operations are generally cut to length (CTL) systems and the design of thinning operation mainly depends on the crane reach (Lamprecht 1990, Spinelli and Nati 2009)
Productivity, energy yield and production costs reflected the effects of the thinning method, with TH7 showing the best operating conditions, as well as the possibility of improving productive stand characteristics by reducing the application area of systematic thinning
Summary
Thinning is a well-recognized treatment in order to improve increment and quality of the remaining trees (Lamprecht 1990, Campos and Leite 2017). Thinning in Brazil is usually done by the mixed method of full tree row harvest in the stand and selective cutting of trees in adjacent rows (Lopes et al 2017). Wood harvesting operations in thinnings can be influenced by operational characteristics, mainly by the machine traffic inside the stand and the distance traveled by the machine in order to avoid damaging the remaining trees. Every fifth tree row is usually cut and selective cutting is performed in the adjacent tree rows. While providing benefits in the productive characteristics of the forest stand, this increase can provide improvements in the operational aspects of wood harvesting
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