Elevation and topography shape the diversity of mesoscale landscape-level woody plant species found in temperate evergreen forests

Plant species richness is influenced by complex interactions between biotic and abiotic factors that operate on different spatial scales. Since spatial scales vary continuously in nature, it is expected that multiple factors simultaneously affect species richness and composition at an intermediate spatial scale (i.e., the mesoscale landscape level). Previous studies have shown that local topography and elevation are important factors for shaping mesoscale landscape-level plant species richness; however, the relative importance of these factors has rarely been examined. Here, we used spatially explicit woody plant survey data to investigate the relative importance of topography, elevation, and disturbance at the mesoscale landscape level. We found that topography and elevation are important drivers of plant species richness and composition at the mesoscale landscape level and affect different components (i.e., the number of species and species composition, respectively). Our study also found that closely-related species coexisted along the elevational gradient, suggesting that niche partitioning among closely-related species is a fundamentally important feature of mesoscale species richness pattern. Furthermore, we found that specialization in a habitat of closely-related species can be established even within a limited environmental gradient. This suggests that biotic interactions among closely-related species may be an important factor driving habitat specialization, and biotic interactions may play an important role in shaping landscape-scale biodiversity patterns.