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Revista mexicana de ciencias forestales

versão impressa ISSN 2007-1132


TAMARIT-URIAS, Juan Carlos. Ordinary least squares, or stochastic frontier regression to estimate the maximum density line with Yoda equation?. Rev. mex. de cienc. forestales [online]. 2023, vol.14, n.76, pp.120-145.  Epub 19-Jun-2023. ISSN 2007-1132.

Accurate determination of the self-thinning line using size-density functions together with density management guidelines (DMGs) are fundamental inputs for managing stand density. Objectives: (1) to compare linear ordinary least squares (OLS) parameter fitting techniques combined with criteria to shift the mean line and stochastic frontier regression (SFR) to determine the self-thinning line with the Yoda equation; (2) to generate a DMG for Pinus montezumae in Puebla, Mexico. Ninety circular 0.10 ha sampling sites were used, located in a high density condition, covering a wide range of ages and growth conditions. The variables number of trees (N) and average volume per tree (aV) were scaled to one hectare. For OLS, theoretical criteria were applied in order to modify the value of the intercept (parameter α) and move the average line to the upper boundary of the observations; for the SFR, the semi-normal model (SNM), the truncated normal model (TNM) and exponential normal model (ENM) modalities were evaluated. With the criterion of using the aV and N of the site with the maximum stand density index to increase the intercept parameter, the OLS, a self-thinning line similar to the SFR modes is reproduced. Therefore, SFR-SNM was selected to reproduce it. The density index of the Yoda stand was 9.2 m3. With a specific allometry and 100 trees ha-1 as reference density, Langsaeter's growth zones were delimited to form the DMG, which is useful for prescribing thinning regimes.

Palavras-chave : Thinnings; stand density; law of -3/2; OLS or SFR; size-density model; Pinus montezumae Lamb.

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