A generalized nonlinear height–diameter model with mixed-effects for seven Pinus species in Durango, Mexico

Abstract

Durango is the major state for timber production in Mexico (28.5 % of the national total); it is estimated that the area under use is 2 million hectares, which is why forest management is an important task for forestry managers. The height-diameter relationship (h-d) is mainly used to describe the structure of a stand, to estimate the individual-tree total volume or stand level volume and to assess the site quality. In this study, a generalized equation was developed for the h-d relationship of seven conifer species in mixed-species forests in northwestern Durango, Mexico. The equation considers diameter at breast height, dominant height, stand basal area and density as independent variables. The nonlinear mixed effect model procedure was used to fit data coming from 44 permanent sample stem-mapped plots. The generalized model explained 82 % of the total variability. Model calibration involved measuring the tree total height in a sample of three trees of average diameter class for each plot. The equation developed could be used as a biometric tool for forest management in mixed forests of the study area.