Taper Equations for Pinus elliottii Engelm. in Southern Paraná, Brazil

Taper equations are the best way to estimate volume for sawtimber or biomass purposes. Thus, this study aimed to assess the performance of different types of taper equations for slash pine with data obtained from fast-growing plantations in southern Brazil. The best results were obtained with Kozak's 1988 equation, contrasted with the results of newly developed equations. We used the mixed-models theory to provide estimation of random parameters for each diameter class. This approach provided better-fitting statistics up to a point from which the addition of more random effects reduces the fit statistics due to their parsimonious nature. As our model lacks the need for individual tree calibration, it has more field applicability than the commonly developed mixed models. The model developed in this study showed to be superior to the commonly used models in Brazil to predict stem diameters and individual tree volume for sawtimber or biomass.