TAPER FUNCTIONS FOR Eucalyptus urophylla CLONES ESTABLISHED IN COMMERCIAL PLANTATIONS IN HUIMANGUILLO, TABASCO, MEXICO

Abstract

Taper functions allow modelling stem profile, estimating the dimensions of tree sections and the timber-yielding volume per type of products, and planning forest supply. The objective of this study was to develop a function that allows modelling the stem profile of Eucalyptus urophylla S. T. Blake clone trees established with commercial purposes in Huimanguillo, Tabasco, Mexico. With 2,133 pairs of data from 93 trees, ten taper models were fitted with the maximum likelihood method. The best model was selected according to the lowest values of the root mean square error (RMSE), the coefficient of variation, the bias and the highest adjusted coefficient of determination (R2 aj.). The fifth-degree polynomial model was the best statistically to model the stem profile of E. urophylla clones, because it includes the relative proportion of the height in each section of the total height. Autocorrelation was corrected by including in the fiiting a CAR(1) type autocorrelation structure. The polynomial model estimates in a reliable way the diameter and the height in clone trees from commercial plantations of E. urophylla.