Height-Diameter Models for Araucaria angustifolia (Bertol.) Kuntze in Natural Forests

The height-diameter relationship of Araucaria angustifolia trees in different sociological positions (dominant, codominant, dominated) was evaluated in a native forest in the south of Brazil, aiming to find accuracy in its estimation and its use as a component of forest description, growth and yield. The total number of trees of the three sociological positions was 657. Part of these trees of each sociological position was used to estimate the parameters of models, and the remaining for model evaluation. Thus, the objective of this work was to find the best height estimate using nonlinear models, linear with dummy variable, principal component with nonlinear regression, and principal component with mixed nonlinear regression. The criteria for accuracy of fit were adjusted coefficient of determination, root mean square error and mean error. The results showed that the fit using principal component with mixed nonlinear regression obtained consistent results and better accuracy. It showed that height growth capacity depends on the sociological position.