Pinus hartwegii Lindl. Forest, structure and composition along of its elevational distribution in the Nevado of Toluca

Abstract

Knowledge of the structure and composition of a forest makes it possible to understand the dasometric attributes of trees and ecosystem processes along altitude-derived vegetation gradients. The structure of the Pinus hartwegii forest was analyzed at an altitude of 600 m on the Nevado of Toluca. Clusters of 1 ha were established at each altitude; dasometric variables were registered. The vertical and horizontal structure was assessed based on the tree density (7D), basal area (BA), and structural parameters and indices. The latter showed that P. hartwegii maintains its abundance and dominance along the studied altitudinal gradient, mainly between 3 700 and 4 000 m, where it forms monospecific forests. The contribution to the tree structure decreased from 100 % at 3 900 and 4 000 m to 45 % at 3 500 m. The dasometric parameters indicated a higher TD in individuals in diameter classes of 5-15 cm at altitudes below 3 800 m; this showed that regeneration may be more limited at higher altitudes, possibly due to irregular tree removal. We conclude that the structural composition of the P. hartwegii forest shows an important change in its structure depending on the altitude, as a result of the environment-society interaction through altitude-related land use management, which compromises the structure and function of this ecosystem. We recommend incorporating altitude as a decisive variable in management plans for high-mountain forests.