关键词: 高寒草甸, 放牧强度, 细根, 养分, 化学计量学

Abstract: Grazing affects plant carbon sequestration and nutrient cycles, changing the carbon (C), nitrogen (N) and phosphorus (P) stoichiometry in grassland ecosystems. Here we examine how grazing intensity influences the fine-root C:N:P stoichiometry in Tibetan alpine meadows. We conducted a long-term (9 years) experiment of the effects of four grazing intensities (ungrazed, light, moderate and heavy grazing) on an alpine meadow on the eastern Tibetan Plateau. Light and moderate grazing increased fine-root C and N concentrations and the N:P ratio, but decreased the C:N ratio, whereas heavy grazing had no effect on C:N:P stoichiometry. The fine-root C:N:P stoichiometry differed among the plant functional groups at different grazing intensities. In addition, grazing intensity indirectly affected fine-root C:N:P stoichiometry by changing aboveground biomass and soil physicochemical properties. Overall, we found that grazing intensity regulated fine-root C:N:P stoichiometry in alpine meadows by changing aboveground biomass and soil physicochemical properties. Our findings have important implications for improving alpine meadow ecosystem protection by implementing sustainable grazing intensities on the Tibetan Plateau.

Key words: Alpine meadow, grazing intensity, fine root, nutrient, stoichiometry