Elevation gradient distribution of indices of tree population in a montane forest: The role of leaf traits and the environment

Abstract

To disentangle the controls on species distribution in the context of climate change is a central element in proposed strategies to maintain species diversity. However, previous studies have focused mainly on the roles of abiotic factors (e.g., climate and soil properties), with much less attention given to the roles of biotic factors such as functional traits. Here, we measured eight leaf traits for 240 individual trees of 53 species and analyzed the variation in traits and population composition indices and their relationships with soil properties, climate factors, and leaf traits. The tree density, frequency and species importance values of the overall species and saplings significantly increased with increasing elevation, while the same indices (except for species frequency) of adults did not significantly change. The largest percentage of variation of species importance value (greater than 50%) was explained by climate, but leaf traits played a critical role in driving elevation distribution patterns of both saplings and adults; the abundance of saplings significantly increased with elevation, with increased leaf carbon contents, while the abundance of adults did not change in accordance with a nutrient conservation strategy associated with the leaf economic spectrum. Our results suggest that the elevation gradient distribution of woody plant species is dependent on tree size and that local atmospheric humidity and leaf traits cause considerable variation in species distribution along subtropical mountain elevations. We provide evidence of which leaf traits play a key role in the elevation gradient distribution of different sizes of woody tree species.