Effects of nitrogen, phosphorus addition and drought on leaf stoichiometry in dominant species of alpine meadow

    Objective   Global change has substantially changed soil nitrogen (N), phosphorus (P) and water availability, which further impacts plant growth and physiological processes. However, so far few studies have been conducted to analyze the interaction effects of soil N, P and water on plant growth and physiological traits, especially for alpine meadow plants. This study aims to reveal the impacts of N addition, P addition, drought and their interactions on plant growth, leaf N and P content and N:P ratios in dominant species of alpine meadows, providing scientific evidence for grassland management.

    Method   Based on an experiment of N addition (10 g/(m²· year)), P addition (10 g/(m²· year)) and drought (50% rainfall reduction) in an alpine meadow of northwestern Sichuan, we measured aboveground biomass, leaf N, P content and their ratio in Elymus nutans, Deschampsia caespitosa and Anemone rivularis. Then we analyzed the influence of different treatments and their interactions on plant biomass and leaf nutrient.

    Result   For plant growth, N addition significantly increased plant biomass of three species, but the impacts of P addition, drought, and the interactions among different treatments were not significant. For leaf nutrient, N addition significantly enhanced leaf N content and N:P ratio of three species, and P addition also promoted leaf P content but reduced N:P ratio. Drought raised leaf N content of E. nutans and D. caespitosa, but had no significant effect on leaf P content and N:P ratio. The interaction of N addition and drought promoted leaf N content and N:P ratio of E. nutans and D. caespitosa. Nevertheless, the interaction of N and P addition was not significant for leaf nutrient of all species.

    Conclusion   This study indicates that alpine species have quite different responses of plant growth versus nutrient traits to nutrient enrichment, drought and their interactions. N input mainly facilitates plant growth, but the complex impacts of soil N, P, drought and their interactions all affect plant nutrient and stoichiometric balance. These results imply that more future studies are needed to detect the mechanisms underlying alpine plant physiological responses to the interactions of various global changes.