FITTING SEVEN TAPER FUNCTIONS TO STEM PROFILES OF Pinus hartwegii Lindl. TREES OF NORTH-EASTERN MEXICO

Abstract

The objective of this study was to evaluate the goodness of fit of seven tapering functions to 109 stem profiles of Pinus hartwegii trees in northeastern México. Trees were cut during forest management operations and diameter of several stem sections was measured. In total, 1613 observations of diameter-height were used to fit the seven taper functions of Clutter, Biging, Amidon, Rustagi & Loveless, Kozak1, Kozak2 and the Variable-Form of Newnham by least square techniques in linear an non-linear regression analyses. The taper functions were fitted to stem profiles of 20 additional trees (307 observations) of the same species. To test the goodness of fit, estimators of the coefficient of determination and the standard error, as well as bias in diameter and volumes were estimated. The results showed that the Variable-Form taper function described best the stem profiles and volumes of the 20 test-trees. Therefore, this taper function is recommended to estimate any of the described parameters.