Abstract: Aims The Qinghai-Tibet Plateau exhibits deficient soil available nutrients, and nutrient addition is commonly employed to alleviate nutrient limitations in alpine meadows. However, previous studies have demonstrated inconsistent effects of nutrient addition on community diversity. The aim of this study was to investigate more accurately that the effects of nutrient addition on the biodiversity and community composition of alpine meadow communities at different altitudes. Methods From 2021 to 2024, we added nitrogen, phosphorus and both nitrogen and phosphorus at three altitudes (3200 m,3700 m and 4050 m), and conducted community surveys at the peak of growing season each year. We calculated α-diversity index (species richness, Shannon-Weiner index, Insimpson index and Pielou evenness index) and β-diversity index (Bray-Curits distance and Jaccard distance), and quantified the relative abundance and species richness of different functional groups. Important findings (1) The α-diversity of low elevation communities is insensitive to nutrient addition, but of middle elevation decreases with nitrogen addition, remains unchanged with phosphorus addition, and increases with both nitrogen and phosphorus additions. High elevation communities exhibit a highly significant positive effect on nutrient addition. The differences in the response of α-diversity to nutrient addition are mainly due to the abundance and diversity of different functional species affected by nutrient addition, in particular, the colonization and local extinction of some rare species in different eleevation. (2) nutrient additions enhanced β-diversity at low and middle elevations but induced community homogenization at high elevations. Taken together, this study revealed the differential response of different elevations of alpine meadows on the Tibetan Plateau to nutrient addition, and clarified the effects of nutrient addition on community diversity and composition.

Key words: alpine meadows, α-diversity, β-diversity, nitrogen addition, phosphorus addition