Biogeographic patterns of multi-element stoichiometry of Quercus variabilis leaves across China

The variability of leaf stoichiometry has been studied at different taxonomic levels across various geographic ranges. However, the intraspecific variations in leaf stoichiometry of widely distributed species are poorly understood. We characterize the biogeographical patterns and environmental controls of leaf nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S) concentrations of Quercus variabilis Blume, a widely distributed tree species of significant economic and ecological value in China. The stoichiometry of Q. variabilis leaves exhibited substantial variation, which was strongly affected by climatic factors and respective concentrations of soil nutrients but had little association with leaf mass per area. Climate was the dominant driver, apart from P and Ca, which were also strongly related to soil P and Ca, respectively. Concentrations of leaf N, P, K, and Mg decreased significantly with mean annual temperature and increased with aridity, albeit at different magnitudes, resulting in positive latitudinal trends of all elements except for Ca and S. The results indicate that Q. variabilis leaf stoichiometry shows a relevant degree of flexibility and that alterations in climatic factors and soil nutrient availability have diverse influences on patterns of the different elements. Our findings provide an important contribution toward an understanding of how widespread species regulate their stoichiometry to adapt to heterogeneous environments.