Accurate volume estimate is a crucial variable for effective forest management in the tropics. In this study, we investigated volumetric models for Tapirapé-Aquirí National Forest in Carajás, PA, Brazil, based on 55 cubed trees by obtaining dbh, stem commercial height, and solid stem volume. A total of 8 double- and 4 single-entry models were tested for minimum dbh at 14 cm. Statistical procedures, such as coefficient of determination (R²), distribution of residuals, and standard error of estimate, were used to evaluate the accuracy of the estimates. Among simple-entry models, Husch logarithmic model showed the best fit to the data (R² = 0.9105), whereas Schumacher & Hall logarithmic model showed the best performance among double-entry models (R² = 0.9942). One previously published regression model, developed for Tapajós National Forest, and a taper function with a form factor of 0.70 were also cross-validated against the trees of this study. These two models subestimated the true volume. This study therefore highlights the importance of developing local volumetric models in order to obtain accurate estimates.
Volume equations; logarithmic model; tropical forest; forest management; Carajás