Short-term effects of experimental trampling on alpine grasslands in Shangri-la, China

Alpine grasslands provide essential ecosystem functions and services, yet they are increasingly subject to anthropogenic perturbations. Northwest Yunnan (NWY) is one of the most popular tourist destinations in China, and alpine grasslands of NWY are particularly susceptible to human recreational activities such as hiker trampling. However, studies that explicitly evaluate the effects of trampling disturbance on alpine communities of NWY are very limited, let alone research testing the responses of these communities to trampling from a functional trait perspective. The present research is performed in alpine grasslands within and outside of a core nature conservation area of Shangri-La, NWY of China, to study species- and community-level responses of alpine communities to simulated trampling through a functional trait-based approach. The results showed that although species-specific differences existed, alpine plants generally showed rapid morphological changes in response to trampling disturbance. At the community level, trampling disturbance caused strong shifts in taxonomy-based diversity metrics (e.g., species richness, Simpson’s index and Shannon’s index) and functional trait-based diversity metrics (e.g., functional richness, functional evenness, functional divergence, and community-weighted mean trait values). Specifically, increased trampling intensity led to a decrease in taxonomic diversity. Meanwhile, functional richness decreased, while functional evenness and functional divergence increased with an increase in trampling intensity. Also, characteristics of alpine community traits had changed towards those with shorter height, reduced leaf size and lower LDMC, and such strong shifts in taxonomic and functional diversity might further affect the functioning and value of alpine grasslands. Therefore, the protection of high-altitude natural grasslands with high sensitivity and vulnerability is urgent, especially as they are increasingly experiencing multiple environmental and climatic stressors nowadays.