Environmental filtering and spatial processes shape the beta diversity of liana communities in a valley savanna in southwest China

Questions: Lianas contribute substantially to the diversity and function of ecosystems. What is the relative importance of environmental filtering and spatial processes on structuring liana beta diversity at taxonomic, functional and phylogenetic levels? Is there any synergy between these drivers (environmental factors and spatial distance) on shaping these three dimensions of beta diversity in a savanna liana community?. Location: A dry-hot valley savanna in Yunnan Province, southwest China. Methods: We established 30 20 m × 20 m plots in the savanna to collect data on the distribution of 22 liana species, 19 functional traits, and plot-level soil nutrients, elevation, and slope. The relative contributions of these environmental factors and spatial distance to liana taxonomic, functional and phylogenetic dissimilarity were analyzed using multiple regression on distance matrices. We also tested which environmental factors influence the beta diversity of liana community using permutational multivariate analysis of variance. Results: Both environmental and spatial distances were significantly correlated with taxonomic, functional and phylogenetic dissimilarity. Spatial distance explained more variation in taxonomic beta diversity than environmental factors. But for both nearest-neighbour functional and phylogenetic distance D_nn’, environment explained relatively more variation than space did. Moreover, the proportion explained by environmental variables was ranked in decreasing order as follows: functional D_nn’, phylogenetic D_nn’, and taxonomic beta diversity. We found soil pH had the highest contribution to taxonomic and functional beta diversity, while soil total nitrogen contributed most to phylogenetic beta diversity. Conclusions: This study revealed that liana taxonomic, functional and phylogenetic beta diversity in the studied hot-dry savanna ecosystem is affected and maintained by both environmental filtering and spatial processes. Moreover, the functional and phylogenetic diversities were more strongly subject to environmental filtering. Our study provides information on the mechanisms underlying liana diversity maintenance in savanna, which is necessary to inform conservation management in this vulnerable ecosystem.