HEARTWOOD FUNCTIONS AND COMPATIBLE TAPER AND MERCHANTABLE VOLUME SYSTEMS FOR Acacia mangium Willd. IN, TABASCO, MEXICO

Abstract

In the last 20 years in Mexico, 30 % of the plantations supported by the Comisión Nacional Forestal (National Forestry Commission, CONAFOR) were made for timber purposes and established in the states of Tabasco, Veracruz, and Campeche, in Mexico. The economic valuation and management of plantations for these purposes are optimized by estimating the timber volume by type of product. The objectives of this study were to fit three compatible systems of segmented equations of taper and merchantable outside-bark volume; identify functions of taper and cumulative volume of heartwood; and analyze the dendrometric types based on the system developed by Fang et al. (2000) for plantations of clonal trees of Acacia mangium Willd., located in Huimanguillo, Tabasco, Mexico. Ninety-one (91) trees (2, 3, 7 and 8 years old) were cut down and two data groups were formed: 60 trees for fitting, and 31 for validation. The stem volume per section was calculated using the overlapping bolts method. The selection of the models was made according to the classification of four goodness-of-fit statistics. The system developed by Fang et al. (2000) showed reasonable estimates with both groups of measurements. The heartwood volume function overestimated the average percentage of heartwood relative to the inside bark volume in 2-year-old trees. However, it estimated them logically for the other ages: 34.7 % at 3 years, 61.8 % at 7 years, and 67 % at 8 years. The ratio heartwood taper to inside bark taper decreased after reaching 70 % of height.