Taper equations for Pinus taeda plantations in Southern Brazil

Abstract

Non-linear regression was used to fit taper functions with data from Pinus taeda plantations in Southern Brazil. Five models were evaluated: Kozak et al. (1969); a fifth-degree polynomial; Max and Burkhart (1976); Parresol et al. (1987); and Clark et al. (1991). Diameter prediction at 12 points along the stem was made to verify the accuracy and precision of these models. Furthermore, their ability to predict total and merchantable (7 cm and 25 cm top diameter) volumes was evaluated. Most of the statistics indicated that the segmented form-class model of Clark et al. (1991) was the best for estimating diameters along the stem and for predicting merchantable or total volume. However, the statistics also indicate regularity and good performance from the Max and Burkhart (1976); Parresol et al. (1987) and fifth-degree polynomial models.