ABSTRACT Background: Tree height is an important variable in forestry, as it is commonly used to estimate volume and biomass, and to evaluate site productivity. In this study, we developed four generalized equations to model height-diameter ( h-d) relationships for coniferous and broadleaf species. For this purpose, we used information from 49 permanent sampling plots located in the natural forests of Puebla, Mexico. Non-linear fixed and mixed-effects modeling approaches were used to fit generalized versions of the Gompertz function to Pinus patula and the Pinus group, the Näslund function to Abies religiosa, and the Curtis function to the Quercus group. Results: Stand variables included in the models were the number of trees per hectare ( N), quadratic mean diameter ( dg), and basal area per hectare ( G). The results showed a model efficiency (EF) = 0.91 and root mean square error (RMSE) = 2.04 for P. patula, as well as an EF = 0.91 and RMSE = 1.63 for the Pinus group. The EF and RMSE for Abies religiosa were 0.88 and 2.21, while for the Quercus group these values were 0.72 and 1.9, respectively. From the mixed-effects model calibration, only a sub-sample of three trees from different quantiles of the diameter distribution is required to make accurate predictions. No stand-level variables related to tree height are included in any of the selected models, thus no additional measurements beyond tree diameter are required. Conclusion: Compared to conventional non-linear least squares (ONLS), mixed-effects models are more flexible and accurate and represent a new tool for sustainable forest management of natural forests in the study area.

This paper describes a user-friendly computer application developed for forest management planning in El Salto, Durango (Mexico). The computer program BWINPro7 version El Salto allows for forest growth and predicts future stand development. It represents an easy tool that can be used by forest managers and owners of forest lands in the decision-making process. The program incorporates individual tree growth models developed for most pine and oak species during recent years in mixed and uneven-aged forests in the north-eastern region of Mexico. Specifically, the models that were incorporated into the program BWINPro7 are: (1) models to estimate crown width and the height to the live crown base, (2) individual tree basal area and height growth models, and (3) a model to predict individual tree mortality. In addition, the simulator can be used in permanent sample plots to describe stand spatial structure, and to prescribe thinning and timber harvest at industrial scale.

Se describe el simulador de crecimiento y producción de rodales forestales BWINPro7 versión El Salto, Durango. Es una herramienta de sencillo manejo para ser utilizada por gestores y propietarios forestales como apoyo a la toma de decisiones en el manejo forestal. El programa incorpora modelos de crecimiento de árbol individual, desarrollados en los últimos años para las principales especies de pino y encino de los bosques mixtos e irregulares del noroeste de México. Específicamente, fueron incorporados al simulador de crecimiento BWINPro7: 1) modelos para estimar el diámetro de copa y la altura de fuste limpio, 2) modelos para la estimación del crecimiento en altura y área basal de árboles individuales y, 3) un modelo para la cuantificación de la mortalidad natural. Adicionalmente, el simulador puede ser usado con parcelas permanentes de inventario para describir la estructura espacial y prescribir cortas de aclareo y aprovechamientos forestales a escala industrial.