Impacts of topography and canopy height on tree diversity patterns at a major montane ecosystem in central China

Mid-elevational peaks are common trends in the elevational diversity of many taxa. Climate is believed a major driver for the elevational pattern of tree diversity in global forest ecosystems. However, it is unclear whether this pattern occurs at the Dabie Mountains, a major old-growth montane ecosystem and the main watershed between the Huai and Yangtze Rivers in central China. In order to assess the elevational diversity pattern of trees at the Dabie Mountains, 22 forest plots of 400 m 2 were established at the northeast and southwest directions to the main peak along an elevational gradient from 404 to 1587 m. In total, 1404 trees of 111 species and 80 genera were identified, where richness ranges from 6 to 22 species and two endemic pine species contribute to 48.9% of Bray-Curtis dissimilarities among the plots. Mid-elevational peaks are present in Shannon, Simpson, and Pielou's evenness indices at around 900 m above sea level, but not in richness or beta diversity of tree species. Canopy height is positively associated with richness and richness difference component of tree species among the plots. Moreover, slope, terrain ruggedness and topographic position, but not elevation, affect replacement and abundance difference component of tree species among the plots. These results suggest that the elevational diversity patterns of trees in the old growth montane forests at the Dabie Mountains may be shaped by multiple factors under different mechanisms. Considering the complexity of diversity patterns and the ecological values of this major montane ecosystem, it is necessary to conserve the forests at the Dabie Mountains.