Abstract: Ecosystem stability is a fundamental attribute that underpins the delivery of essential ecosystem services. However, most research has primarily focused on the temporal stability of biomass, overlooking the multidimensional nature of stability that cannot be captured by a single metric. In this study, we investigated the effects of nitrogen (N) and phosphorus (P) additions on the stability of plant and microbial communities in alpine meadows of the Qinghai-Tibet Plateau. Our results demonstrated that N and P additions significantly increased plant community biomass but reduced the diversity of plants, prokaryotes, and fungi. Although N and P additions did not significantly reduce biomass stability, a decreasing trend was observed. More importantly, compositional stability was significantly reduced by nutrient additions, with differing underlying mechanisms. Nitrogen addition primarily reduced community compositional stability by decreasing prokaryotic diversity, affecting plant diversity and the stability of subdominant species. In contrast, P addition mainly reduced the compositional stability of dominant species, thereby decreasing overall community stability. Furthermore, N addition significantly decreased the network stability of both prokaryotic and fungal communities. Importantly, microbial diversity and network properties were significantly correlated with plant community stability, highlighting the interconnectedness of above- and belowground communities. Our findings emphasize the need for future research to adopt a multidimensional approach to ecosystem stability, integrating both compositional and functional aspects of plant communities, and incorporating microbial diversity and network characteristics.

Key words: Ecosystem stability, Nitrogen, Phosphorus, Alpine meadow, Microbial diversity, Community compositional stability