Diversity and structure of the cloud forest in the Sierra Madre de Chiapas, Mexico.

Introduction: Cloud forests are noted for their narrow distribution in tropical mountain systems. Floristically, they are complex and heterogeneous, with gaps in information that hinder the understanding of how their diversity and structure vary.Objective: To analyze patterns of diversity, structure, and composition of the cloud forest in Mexico.Methods: We counted and measured woody plants in forty 0.1 ha plots from five sites in approximately 200 km along the Sierra Madre of Chiapas, Mexico (1 700 - 2 100 m.a.s.l.). We used three statistical methods: analysis of variance (diversity true and structure among sites), simple regression and multivariate statistics (climate and Results: We recorded 4 021 individuals (220 species, 60 families). In true diversity, we only found differences for species richness, with a slight increase toward the central part of the area. Diversity was constant for common and dominant species. We found no differences in tree density or basal area between sites. However, there was less density and more basal area at higher elevations. Beta diversity and differentiation in floristic composition are high and important between plots of the same site, and they increase with distance between sites.Conclusions: Beta diversity and floristic differentiation significantly contribute to variation in the cloud forest. Climatic variables and altitude have different effects on diversity and structure.