Structural characterization of oak-dominated montane forests in west-central Mexico

Abstract

Olvera-Vargas,  M.,  Figueroa-Rangel,  B.L.  (2012).  Structural  characterization  of  oak-dominated  montane  forests  in  west-central Mexico. Ecosistemas 21(1-2):74-84

Three floristic associations dominated by oaks (Quercus spp) in montane forests in west-central Mexico were studied in order to discern population differential structure among them. Eighty-four circular plots were established along a 10 km environmental gradient. Structural characterization included density, basal area, diametric distributions and index of  performance (IP); the IP estimated through the sum of relative density and volume of each species by association. The analysis consisted of an estimation of the Gini coefficient (G) to determine diameter distribution equality, a non-parametric test to evaluate differences in diameter sizes for the six more important species among the three floristic associations, and a general lineal model to determine the effect of the species and the floristic association in diameter sizes. Results indicated that there is structural differentiation among species in relation to the floristic association. The floristic association with the largest number of oak species (eight species) coexisting in the canopy presented intermediate values of IP and the highest inequality (G) in diameter sizes; only three species showed statistical significant differences in diameter sizes among associations. Species structural differentiation by association, in particular oak species diameter size, seems to be a species strategic response to share site resources, proportional to their sizes, in order to coexist in the canopy.