Abstract
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 angiosperm species within 120 plots of 20 m x 20 m each. The plots were located at eight study locations separated by ~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 α- and γ-diversity display a hump-shaped relation to elevation peaking at 2500 m and 3000 m, respectively. The relative contribution of between-habitat β-diversity to γ-diversity also showed a unimodal hump whereas within-habitat β-diversity declined with elevation. Forest-use intensity did not affect α-diversity, but β-diversity was high between old-growth and secondary forests. Overall, γ-diversity peaked at 2500 m (72 species), driven mainly by high within- and among-habitat β-diversity. We infer that this belt is highly sensitive to anthropogenic disturbance and forest-use intensification. At 3100 m, high γ-diversity (50 species) was driven by high α- and within-habitat β-diversity. There, losing a specific forest area might be compensated if similar assemblages occur in nearby areas. The high β-diversity and endemism suggest that mixes of different habitats are needed to sustain high γ-richness of terrestrial herbs along this elevational gradient.
Highlights
The majority of biomes are undergoing rapid changes, especially in the tropics [1]
This study aims to assess how herbaceous angiosperm diversity varies along elevational gradients in the tropics and how those patterns are affected by variation in forest use intensity
Elevation2, habitat, mean annual temperature (MAT), MAP2, interactions between elevation and elevation2, an interaction between elevation and MAT, as well as an interaction between elevation2 and MAT modeled best the α-diversity (Table 3). This model explained a large amount of the variance in species richness (GLM R2 = 0.69)
Summary
The majority of biomes are undergoing rapid changes, especially in the tropics [1]. Growing human pressure on ecosystems poses a marked threat to global biodiversity. Herb diversity along gradients of elevation and forest-use intensity. The research of TK was supported by CONACyT. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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