Effects of abiotic and biotic factors on woody plant diversity across vertical strata in a temperate forest

Broad-leaved deciduous forests in the transitional region from temperate to subtropical climate in China exhibit a diverse assemblage of species. The effects of potential biotic and abiotic factors on forest species diversity are currently of great interest. Here, we quantified the diversity of woody plant species across vertical strata in a fully recorded 25-ha permanent forest dynamics plot (500 × 500 m) in the Mts. Qinling of China using 4 indices: Pielou evenness index (\({J}_{SW}\)), Shannon entropy (\(H\)), species richness (\(S\)), and species abundance. Analysis of multivariate linear regression was employed to compare the influences of potential biological, topography, and soil variables on the alpha diversity for each of the 625 sub-plot (20 × 20 m) in the canopy layer, substory layer, and understory layer. The results displayed that the indices of the alpha diversity significantly varied among different forest vertical strata and they were mostly and significantly related to the DBH structure variable, soil available phosphorus (P), and altitude. Despite vertical strata of the studied forest, biological, topographic, and soil factors jointly showed reasonably strong explanatory power for species diversity. More than 12% of the variations of the alpha diversity in canopy layer and 16% in substory layer as well as 8% in understory layer could be collectively explained by biological, topographic, and soil factors. Our findings can contribute to the understanding of how environmental and biological factors interact to affect species diversity and thus are of great implication for the preservation of forest species diversity.