Solar radiation regulates the leaf nitrogen and phosphorus stoichiometry across alpine meadows of the Tibetan Plateau

Leaf nitrogen (N) and phosphorus (P) stoichiometry covary with many aspects of climatic and edaphic factors, yet the effects of solar radiation (SR) on leaf stoichiometry are still unclear. In the Tibetan Plateau, the high level of SR can induce the plants to reach their light saturation point easily, which causes photoinhibition of photosynthesis. Here, the leaf N and P concentrations across the alpine meadow of the Tibetan Plateau were measured to explore the response of leaf N and P stoichiometry to SR. Our results showed that the concentrations of both leaf N and leaf P were negatively correlated with SR under the high SR level (SR > 15,000 KJ m(-2)d(.1)). The structural equation model demonstrated that SR plays a vital role in leaf N and P stoichiometry, and SR has direct effects on leaf N and P stoichiometry through a physiological process (path coefficient = -0.293 and -0.343, respectively). In addition, the high SR level lowered the level of precipitation (path coefficient = -0.615) and temperature (path coefficient = -0.047), then changed the soil organic carbon, soil nitrogen and phosphorus content. Furthermore, precipitation, temperature, soil organic carbon, soil nitrogen and phosphorus also regulated leaf N and P stoichiometry, which caused the SR to have indirect effects on leaf N and P stoichiometry (path coefficient = -0.072 and -0.053, respectively). As a consequence, we highlighted that SR regulates leaf N and P stoichiometry across alpine meadows of the Tibetan Plateau, and the results provide guidance on grassland management.