Variation and adaptation in leaf sulfur content across China

Sulfur is an essential functional element in leaves, and it plays important roles in regulating plant growth, development and abiotic stress resistance in natural communities. However, there has been limited information on the spatial variation in leaf sulfur content (LSC) and adaptive characters on a large community scale. Sulfur in leaves of 2207 plant species from 80 widespread ecosystems (31 forests, 38 grasslands and 11 deserts) in China was measured. One-way analysis of variance with Duncan’s multiple-range tests were used to evaluate the differences in LSC among different plant growth forms and ecosystems. We fitted the relationships of LSC to spatial and climate factors using regression. Structural equation modeling analysis and phylogenetic analysis helped us further explore the main factors of LSC variation. LSC ranged from 0.15 to 48.64 g kg–1, with an average of 2.13 ± 0.04 g kg–1 at the community scale in China. We observed significant spatial variation in LSC among different ecosystems and taxa. Overall, LSC was higher in arid areas and herbs. Furthermore, higher LSC was observed under environments of drought, low temperatures and intense ultraviolet radiation. Temperature, precipitation, radiation, soil sulfur content and aridity jointly regulated LSC, explaining 79% of the spatial variation. However, LSC was not significantly related to phylogeny. Our results demonstrate that LSC plays an important role in plant adaptations to extreme environments and further extend our understanding of the biological function of sulfur from the organ to the community level. These findings highlight the importance of sulfur metabolism for our understanding of the impact of global climate change on plants.