Abstract:

Beta diversity refers to species composition variation among communities across temporal and spatial scales. Beta diversity includes species turnover and species richness differences between communities. The ecological processes that drive beta diversity patterns are determined by spatio-temporal dynamics of communities. However, the driving forces that form beta diversity and its components patterns are still controversial. Previous studies have shown that beta diversity patterns are scale-dependent as are the relative importance of underlying ecological processes. In this study, the beta diversity of tree species in the 20 ha subtropical mid-mountain moist evergreen broad-leaved forest dynamics plot in Ailao Mountains was studied. Across different spatial scales, the Bray-Curtis indices among quadrat pairs were partitioned into species turnover components and species richness components. The relative importance of scale dependent environmental filtering and dispersal limitation on beta diversity were analyzed by using a redundancy analysis and variation partitioning analysis. Our results showed that: (1) Beta diversity and its components decreased with increasing scale. The pairwise difference in species composition between quadrats was dominated by species turnover components at all scales. (2) With increasing scale, the relative importance of environment filtering on beta diversity gradually increased, while the relative importance of dispersal limitation gradually decreased. This study confirmed the importance of spatial scale on beta diversity pattern and the quantitative assessment of its driving forces. Future research should focus more on examining the mechanism of the scale effects on beta diversity and its underlying driving forces.

Key words: community composition, beta-diversity component, variation partitioning, environment filtering, dispersal limitation, Ailao Mountains