MODELING OF FORWARDER PRODUCTIVITY AND COSTS IN THINNED PINE STANDS

AbstractThe aim of this study was to assess the influence of some operational variables on the forwarder productivity and production cost in thinned Pinus taeda L. stands by means of mathematical modeling. This study was carried out in a forest company located at Quedas do Iguaçu, state of Paraná, Brazil. Two stands at 9 and 10 years old from sites with high productivity and similar soil and relief features were studied. A time-motion study was applied to determine the operational cycle time, operational efficiency, productivity, and production costs. By means of mathematical modeling, we verified the influence of the variables: age of stand; cycle time; load volume; and extraction distance on the forwarder productivity and production costs. Models were fitted for estimating the forwarder productivity using cycle time, load volume, and extraction distance. Thus, we obtained the determination adjusted coefficients of 0.88 and 0.94, with an estimate standard error between 6.9% and 13.5%. Models for estimating production cost through the load volume variable presented a determination coefficient of 0.64 and 0.86, with an estimate standard error of 23.1% and 26.7%. Such results have shown the possibility of using mathematical models to estimate the performance of forest machines as a tool for planning the timber harvesting operations

FUEL PROPERTIES OF FOREST RESIDUES RECOVERED FROM FULL EUCALYPTUS TREE HARVESTING IN DIFFERENT CHIP PRODUCTION SCENARIOS

This study aims to evaluate the fuel properties of forest residues recovered from Eucalyptus saligna and E. urophylla × E. grandis stands at seven years old in five chip production scenarios. A forest inventory was conducted to estimate the dry biomass, followed by full-tree harvesting with minimum stem diameters equal to 8, 10, 12, and 14 cm for pulpwood, as well as the full trees for energy purposes (treatments). Moisture, volatile matter, fixed carbon, ash contents, and higher and lower heating values of chips were evaluated. The dry biomass was compared between stands by the t-test (α = 0.05) and the fuel properties were assessed between minimum stem diameters in the same forest stand by the Tukey’s test (α = 0.05). Higher chip moisture was obtained in the larger minimum stem diameter, since it showed an increased up to 88% in moisture for the E. urophylla × E. grandis stand. Volatile matter, fixed carbon, and ash results showed that the recovered residues of E. saligna were more susceptible to variations in minimum stem diameters, with up to 53% reduction in ash content between the smallest diameter and full trees. Higher and lower heating values showed non-statistical differences between the minimum stem diameters in Eucalyptus stands

QUALIDADE ESTRUTURAL DO SOLO APÓS O CORTE FLORESTAL POR HARVESTER DE PNEUS E ESCAVADEIRA HIDRÁULICA ADAPTADA

O objetivo foi avaliar a qualidade estrutural do solo após corte florestal com harvester de pneus e escavadeira hidráulica adaptada em LATOSSOLO VERMELHO distrófico típico. O experimento foi delineado de forma inteiramente casualizada com instalação de quatro unidades amostrais com três pontos de repetição. Além disso, foram coletadas amostras de solo na trilha de tráfego dos rodados da máquina nas camadas de 0 a 0,10; 0,11 a 0,20; 0,21 a 0,30; e 0,31 a 0,40 m de profundidade para determinação dos parâmetros de densidade e porosidade total e, também, foi mensurada a resistência do solo à penetração na trilha dos rodados e entre rodados. Dessa forma, foi possível determinar que a densidade e a porosidade total média antes do tráfego das máquinas foram de 1,10 g cm-3 e 53,85%, respectivamente, ocorrendo efeitos significativos nessas variáveis após o tráfego do harvester de pneus em todas as camadas avaliadas. Quanto a resistência do solo à penetração, verificou-se que houve aumento significativo na trilha dos rodados do harvester, tanto de pneus como de escavadeira, contudo, havendo incremento de cerca de 77% na camada de 0,10 m após tráfego do harvester de pneus