Diversity and composition of herbaceous angiosperms along gradients of elevation and forest-use intensity

Terrestrial herbs are important elements of tropical forests; however, there is a lack of research on their diversity patterns and how they respond to different intensities of forest-use. The aim of this study was to analyze the diversity of herbaceous angiosperms along gradients of elevation (50 m to 3500 m) and forest-use intensity on the eastern slopes of the Cofre de Perote, Veracruz, Mexico. We recorded the occurrence of all herbaceous angio-sperm species within 120 plots of 20 m x 20 m each. The plots were located at eight study locations separated by similar to 500 m in elevation and within three different habitats that differ in forest-use intensity: old-growth, degraded, and secondary forest. We analyzed species richness and floristic composition of herb communities among different elevations and habitats. Of the 264 plant species recorded, 31 are endemic to Mexico. Both alpha-and gamma-diversity display a hump-shaped relation to elevation peaking at 2500 m and 3000 m, respectively. The relative contribution of between-habitat beta-diversity to gamma-diversity also showed a unimodal hump whereas within-habitat beta-diversity declined with elevation. Forest-use intensity did not affect alpha-diversity, but beta-diversity was high between old-growth and secondary forests. Overall,gamma-diversity peaked at 2500 m (72 species), driven mainly by high within-and among-habitat beta-diversity. We infer that this belt is highly sensitive to anthropogenic disturbance and forest-use intensification. At 3100 m, high gamma-diversity (50 species) was driven by high alpha-and within-habitat beta-diversity. There, losing a specific forest area might be compensated if similar assemblages occur in nearby areas. The high beta-diversity and endemism suggest that mixes of different habitats are needed to sustain high gamma-richness of terrestrial herbs along this elevational gradient.