Sergio Luis Martins dos Santos

The objective of this study was to evaluate the influence of the mean individual volume per tree (MIV) on the productivity of forwarder machines and the production cost in eucalyptus plantations located in southern Bahia, Brazil. MIV positively influenced the productivity and production costs, promoting a more attractive cost in the latter when the individual volume per tree increased. The machine’s productivity for MIV of 0.13 m³ was 42.06 cubic meters per effective working hour (m³Ewh⁻¹), while the productivity for the MIV of 0.58 m³ reached 60.97 m³Ewh⁻¹, corresponding to an increase of 42.59% between the minimum and maximum MIV classes. The extracted cost (m³) decreased by 30.12% from USD 2.49 to 1.74, respectively, when comparing the minimum and maximum MIV classes. The coefficient of determination obtained in the forwarder productivity modeling was significant (R² = 92%), indicating the machine’s productivity can be explained by the mean individual volume per tree. The highest forwarder yields in the highest average volume per tree (MIV) classes provided better energy efficiency indices for the machine; that is to say, when the forwarder became more productive, the ratio between fuel consumption per cubic meter of timber harvested decreased, providing better performance for the respective index. There was a difference in extraction costs of USD 147.83 per hectare between the lowest and highest productivity forests (MIV varying from 0.15 to 0.58). The mechanical availability and mean operational efficiency of all forwarders evaluated were above 80%, which contributed to effective machine productivity performance. Maintenance and repairs represented the largest portion of operational costs (33.59%), followed by labor (22.49%), depreciation (14.33%), and fuel (10.11%).

The objective of this study was to assess the performance of a feller buncher as a function of forest yields. The feller buncher productivity and production costs were evaluated in a eucalyptus forest with different mean tree volume (MTV) classes. The technical analysis included time and motion study, productivity, mechanical availability, and operational efficiency. The economic analysis was based on fixed and variable costs, which resulted in the feller buncher's total operating cost. Production costs were calculated by the ratio of operating costs to wood volume harvested per working hour, which varied according to the forest yield levels (low, medium, and high) determined based on MTV classes. The results showed a total operating cost of US$157.76 h-1 for the feller buncher, 83.52% attributed to variable costs. The highest operational performance and, consequently, lower production cost were found for the highest MTV, with a tendency for productivity stabilization as the forest yield increases. The time and motion study of the feller buncher operating cycle for the three forest yield levels showed a statistically significant difference by Tukey’s test (5% significance). A significant difference was found in the tree felling and bunching phase among the three forest yield levels, as the feller buncher operating time in low-yield forests was 46.59% greater than that in high-yield forests.