The objective of this study was to evaluate the damage to remaining trees of pine stand submitted to two models of mechanized thinning. Data were collected in the wood harvesting areas of a forest company in Southern Brazil during the first commercial thinning with 10-year-old trees. The thinning was executed by a harvester in cutting the trees and a forwarder in extracting the logs, which was defined by thinning in the 5th planting line (treatment T1); and by a chainsaw in felling the central trees, by a harvester in cutting the other lines, and by a forwarder in extracting the logs in the experimental area defined by thinning in the 7th planting line (treatment T2). The damage to remaining trees in the stand in relation to the dimensions and location of the machinery operating trail was evaluated, and data were analyzed through descriptive statistics. The results showed that treatment T2 caused greater damage in the remaining trees due to greater handling of felled and processed trees and a higher concentration of wood piles in the operating trail of the machines. In addition, there was greater contact of the harvester with the remaining trees when searching for the trees felled by the chainsaw was conducted to perform the final processing. Treatment T1 proved to be more suitable for thinning pine stands.

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.

ResumoOperação de poda em árvores urbanas usando duas plataformas de trabalho aéreo. A necessidade de reduzir riscos de acidentes e esforço físico dos trabalhadores na operação de poda urbana de árvores promove a busca de tecnologias com menor custo de execução. O objetivo foi avaliar o desempenho operacional da poda urbana de árvores com duas plataformas de trabalho aéreo realizadas em árvores de domínio público e privado na Grande Assunção, Paraguai. As plataformas de trabalho aéreo avaliadas foram: articulada e montada em caminhão, em três níveis de trabalho. Através de estudo de tempos e movimentos foram determinados tempos de ciclo de trabalho, eficiência operacional, consumo de combustível e custos operacionais. A amostragem consistiu em 78 árvores, nas quais os valores médios foram comparados entre os níveis de trabalho pelo teste de Tukey (α = 0,05). O tempo de ciclo de trabalho mais longo consumido foi na poda sem movimento da base da máquina, com eficiência operacional média de 86,2 e 76,8% na plataforma articulada e na plataforma montada em caminhão, respectivamente. O consumo de combustível aumentou com os níveis de trabalho e foi mais alto na plataforma montada em caminhão, de 7,33 para 9,33 L h -1 de óleo diesel, a USD 18,93 por hora. Portanto, a plataforma articulada e a plataforma montada em caminhão avaliadas na poda urbana de árvores apresentaram diferentes custos operacionais que aumentaram com o maior nível de amplitude de movimento. O principal motivo foi a intensificação da operação do motor e os gastos de energia exigidos pelo sistema hidráulico das máquinas, especialmente na plataforma montada em caminhão. Palavras-chave: arboricultura, tratamentos silviculturais, estudo de tempos e movimentos.

The need for higher value-added wood products and the high cost of mechanized operations stimulate the development of new thinning methods in order to provide gains in productive capacity of forest stands. In this context, the aim of this study was to analyze the effect of two thinning methods on productivity and costs of the forest harvesting in the generation of multi‐products. The study was carried out in a 10-year-old Pinus taeda stand under to two thinning methods: TH5 (harvester, with systematic harvesting of the fifth tree row and selective in adjacent rows); and TH7 (chainsaw and harvester, with systematic harvesting of the seventh tree row and selective in adjacent rows). We determined the working cycle times, productivity, and production costs through a time and motion study, with the averages of partial and total times being compared between thinning methods by the Wilcoxon-Mann-Whitney test (α ≤ 0.05). From the obtained results, it was found that the thinning methods directly affected the harvester’s partial and total times, with the largest time obtained in the TH7 thinning method due to the need to locate previously cut trees by chainsaw, with a consequent reduction in the productivity and an increase in the production costs when compared to the TH5 method. However, despite the higher production cost, the TH7 method showed potential with the use of mechanization in all activities, making it possible to increase selective thinning and contribute to gains in forest stand quality.