The Relative Importance of Environmental Filtering and Dispersal Limitation on the Multidimensional Beta Diversity of Desert Plant Communities Depends on Sampling Scales

Environmental filtering and dispersal limitation jointly determine patterns of beta diversity, for which little is known about how their relative contribution to beta diversity varies with sample size and the dimensions of diversity in desert plant communities. Here, based on vegetation survey data from the southern margin of the Taklamakan Desert, we investigated the trends of taxonomic, functional, and phylogenetic beta diversity and their turnover and nestedness components across the sampling scale gradients and analyzed the relative importance of environmental filtering and dispersal limitation in community assembly at different sampling scales and different dimensions. Our results revealed the average value of multiple dimensions beta diversity decreased with the increasing sampling scale. Meanwhile, the control effects of spatial and environmental factors on beta diversity differed depending on the sampling scale. In small (5 m×5 m) and middle (20 m×20 m) sampling scales, spatial factor plays a predominant role in beta diversity, while large scales (50 m×50 m) are driven by environmental factors. Although the correlations among the three dimensions of beta diversity were high, the spatial and environmental factors explained them to different degrees. Our study supports the notion that beta diversity is shaped by the combination of environmental filtering and dispersal limitation, but the relative importance of both varies across sample scales and dimensions. Meanwhile, our findings challenge the notion that substituting one aspect of diversity for others is sufficient and highlight the importance of considering multiple sampling scales.