COMPATIBLE TAPER AND VOLUME FUNCTIONS IN A COMMERCIAL FOREST PLANTATION OF Pinus chiapensis (Martínez) Andresen IN TLATLAUQUITEPEC, PUEBLA.

Abstract

Taper, or stem profile functions are practical mathematical tools for quantifying the volume and distribution of products of standing trees. These data are relevant in creating forest management programs for timber production. The objective of this study was to fit different models of total volume, segmented taper functions compatible with merchantable volume, models of total volume within the compatible segmented taper-volume function of Fang, and to analyze the different dendrometric types in the segmented function of Fang. All this to obtain the best volume system for Pinus chiapensis in a commercial forest plantation in Tlatlauquitepec, Puebla, Mexico. Data from 35 felled trees, 3, 5, 6 and 7 years old were evaluated and a total of 485 pairs of observations of diameters and heights along the stem were generated. To calculate stem volume, the overlapping bolts method was used. The segmented functions of Fang, Max and Burkhart showed better precision, evidenced by higher coefficients of determination and lower values in the mean square root of the error, coefficient of variation and average absolute bias. The segmented Fang function suggests two inflexion points. The first occurred at 5% and indicated a geometric change from neiloid to paraboloid, and the second occurred at 50% of the total height, indicating the geometric change from paraboloid to cone. The model of the combined fitted variable in the Fang system denotes a mean form factor of 0.39, closer to a cone than to a paraboloid. The statistical results indicated that the Fang compatible system combined with the Takata total volume model allow precise prediction of taper and of total and merchantable volume.