Abstract

MUNOZ-FLORES, H. Jesús et al. Tapering and implied volume equations for Pinus leiophylla Schiede ex Schltdl. & Cham. in state of Michoacán. Rev. mex. de cienc. forestales [online]. 2025, vol.16, n.89, pp.59-83.  Epub June 30, 2025. ISSN 2007-1132.  https://doi.org/10.29298/rmcf.v16i89.1508.

The description of the taper (di) and the precise estimation of the stem volume (sV) are fundamental in the estimation of the timber stock and the distribution of products. The objective of the study was to fit a taper function and define the implicit sV model for Pinus leiophylla trees in the indigenous community of Patambán, Tangancícuaro, state of Michoacán, Mexico. Eight taper functions were fitted using data from 36 dominant trees from forest plantations (245 normal diameter [d], diameters [di] and heights [Ai] at different stem sections). Mixed effects models (MEM) and the maximum likelihood technique were utilized to correct for heteroscedasticity and self-correlation with the expression varExp: $var\left({\epsilon }_{ij}\right)={exp}^{2\bullet {\delta }_1\bullet v_i}$ and a moving average (ARMA) structure of order (p, q), respectively. Statistically, Clutter’s taper expression: $di=2.256{\times d}^{0.943}{\times \left(Th-Ih\right)}^{1.434+ui}{\times Th}^{-1.617}$ was more accurate as it included the random effect ($ui$) additively in the total height parameter (Th). The explanation of sampling variability was 97.8 %, with an overall estimation error of 1.406 cm and an individual bias of 0.0138 cm. The implicit sV model was Schumacher-Hall: $Sv=1.3150\times Th\times d^{3.8853}$ (d and Th in m). The proposed expressions can be reliably included in the description of inventory data or yield estimates for forest crops.

Keywords : Forest harvesting; Clutter; mixed effects; differentiated market; forest profile; Schumacher-Hall.

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