Abstract:

Aims: In this study, we aimed to test whether the responses of the community diversity and composition of alpine meadows were influenced by elevations and soil nutrient availability. 

Methods: Based on a warming (OTCs) and nutrient addition (nitrogen and phosphorus) experiment across elevations (3,200 m, 3,700 m, 4,050 m), plant community surveys were conducted from 2021 to 2024, and alpha (α) and beta (β) diversity metrics and relative abundance of four functional groups were calculated. The linear mixed effects model, permutation multivariance analysis, one- and two-way ANOVAs, and Tukey’s HSD test were used to analyze the effects of warming and nutrient addition on the community α and β diversity. 

Results: (1) The effects of warming on α diversity were elevation-dependent, showing no significant effects on it at 3,200 m, and reducing it at 3,700 m, and increasing it at 4050 m. Meanwhile, nutrients addition also markedly influenced the responses of α diversity to warming by changing species richness and/or relative abundance of different functional groups. Specifically, under nutrient addition conditions, warming reduced the richness of legumes and grasses at 3,200 m, grasses, sedges, and forbs at 3,700 m, while increased the richness and relative abundance of grasses and forbs at 4,050 m. (2) Similarly, the responses of β diversity to warming were affected by elevations, and nutrients addition regulated such responses. For instance, warming significantly reduced β diversity at 4,050 m; by contrast, under nutrient addition conditions, warming reduced it at 3,700 m and increased it at 4,050 m, respectively. 

Conclusion: Our findings suggest that elevations and soil nutrients strongly regulate the responses of alpine meadow diversity to warming through species richness and/or the relative abundance of four functional groups. Therefore, to more accurately predict the biodiversity response to global warming in the future, it is essential to consider the baseline environmental conditions (e.g., soil moisture and nutrients).

Key words: α diversity, β diversity, relative abundance, warming, nitrogen addition, phosphorus addition, elevation, Qinghai-Tibet Plateau