Plant beta-turnover rather than nestedness shapes overall taxonomic and phylogenetic beta-diversity triggered by favorable spatial–environmental conditions in large-scale Chinese grasslands

Introduction Although it is widely acknowledged that biodiversity maintains plant community assembly processes, exploring the patterns and drivers of beta-diversity ( β -diversity; species variation among local plant communities) has received much less attention compared to alpha-diversity ( α -diversity; species variation within a local plant community). Here, we aim to examine the patterns and spatial–environmental drivers of taxonomic and phylogenetic β -diversity, and their components such as species turnover and nestedness, in large-scale Leymus chinensis grassland communities. Methods We collected plant community data from 166 sites across widely distributed L. chinensis communities in northern China, and then calculated the taxonomic and phylogenetic β -diversity indices (overall, turnover and nestedness) using a pairwise dissimilarity approach. To assess the effects and to explain the variation in the patterns of β -diversity, we collected data on geospatial, climate and soil conditions. We applied descriptive statistics, Mental correlations, and multiple linear regression models to assess the patterns and spatial–environmental drivers of β -diversity. Results The β -turnover, as compared to β -nestedness, exhibited a predominant influence, constituting 92.6% of the taxonomic β -diversity and 80.4% of the phylogenetic β -diversity. Most of the spatial–environmental variables were significantly positively correlated with the overall taxonomic and phylogenetic β -diversity and β -turnover, but not with β -nestedness. Climatic factors such as MAP and MAT were the strongest predictors of both taxonomic and phylogenetic β -diversity and β -turnover. The variance partitioning analysis showed that the combined effects of spatial and environmental factors accounted for 19% and 16% of the variation in the taxonomic and phylogenetic β -diversity (overall), 17% and 12% of the variation in the β -turnover, and 7% and 1% of the variation in the β -nestedness, respectively, which were higher than independent effects of either spatial or environmental factors. Discussion At larger spatial scales, the turnover component of β -diversity may be associated with the species complementarity effect, but dominant or functionally important species can vary among communities due to the species selection effect. By incorporating β -diversity into grassland management strategies, we can enhance the provision of vital ecosystem services that bolster human welfare, serving as a resilient barrier against the adverse effects of climate change at regional and global scales.