Discriminating ecological processes affecting different dimensions of alpha- and beta-diversity in desert plant communities

Understanding the spatial distribution of plant diversity and its drivers are major challenges in biogeography and conservation biology. Integrating multiple facets of biodiversity (e.g., taxonomic, phylogenetic, and functional biodiversity) may advance our understanding on how community assembly processes drive the distribution of biodiversity. In this study, plant communities in 60 sampling plots in desert ecosystems were investigated. The effects of local environment and spatial factors on the species, functional, and phylogenetic alpha- and beta-diversity (including turnover and nestedness components) of desert plant communities were investigated. The results showed that functional and phylogenetic alpha-diversity were negatively correlated with species richness, and were significantly positively correlated with each other. Environmental filtering mainly influenced species richness and Rao quadratic entropy; phylogenetic alpha-diversity was mainly influenced by dispersal limitation. Species and phylogenetic beta-diversity were mainly consisted of turnover component. The functional beta-diversity and its turnover component were mainly influenced by environmental factors, while dispersal limitation dominantly effected species and phylogenetic beta-diversity and their turnover component of species and phylogenetic beta-diversity. Soil organic carbon and soil pH significantly influenced different dimensions of alpha-diversity, and soil moisture, salinity, organic carbon, and total nitrogen significantly influenced different dimensions of alpha- and beta-diversity and their components. Overall, it appeared that the relative influence of environmental and spatial factors on taxonomic, functional, and phylogenetic diversity differed at the alpha and beta scales. Quantifying alpha- and beta-diversity at different biodiversity dimensions can help researchers to more accurately assess patterns of diversity and community assembly.