Abstract: This study aimed to understand the effects of nitrogen (N), phosphorus (P) and potassium (K) deposition that were caused by human activities on plant leaf nutrient traits in alpine grassland ecosystem. A multiple-nutrient (N, P, K) addition experiment with eight treatments was carried out in Bayinbrooke grassland. By measuring leaf C, N and P contents of six common species, we explored the response patterns of leaf nutrient traits to nutrient addition at the species, functional group, and community levels. The results showed that: (1) N addition significantly increased leaf N content, and P addition significantly increased leaf P content of the six species. The effects of mixed nutrient addition on leaf C, N and P contents were complex. (2) Nutrient addition significantly affected the N and P contents in leaves of different functional groups. After N addition, leaf N content in grasses increased significantly by 66.4%. After the addition of P, NP and NPK, the contents of N and P in the leaf of grasses increased significantly. After P addition, the leaf P content in legume increased significantly by 98%. (3) Different nutrient addition treatments significantly affected leaf N and P content at the community level. Under the addition of P, NP, PK, and NPK, leaf N and P contents increased significantly, especially for leaf P content. However, N, K, and NK addition had no significant effect on leaf N and P content. Principal component analysis revealed that soil organic matter, total N, total P content and soil pH were the key factors affecting the variation of leaf C, N and P content at the community level. Among those factors, soil total P was the most critical one, followed by soil organic matter and total N, and the influence of soil pH was relatively limited.

Key words: nutrient addition, leaf nutrient content, species level, functional group level, community level, alpine grassland