Initial plant diversity modulates the effect of nutrient enrichment on grassland stability across a climate gradient in China

Nutrient enrichment can negatively impact the stability of various ecosystems. However, whether these impacts depend on biotic and abiotic factors, such as plant diversity and climate, remains unclear. Here, we investigated how climatic factors and plant diversity affected temporal stability of aboveground net primary production (ANPP) in responses to nitrogen (N) and phosphorus (P) additions and its biotic mechanisms over 4 years across seven Chinese grasslands spanning a climatic gradient (mean annual temperature: −0.38 to 8.75 °C; annual precipitation: 134.60 to 462.40 mm). We showed that N and NP additions significantly reduced temporal stability of ANPP, while P addition marginally reduced the temporal stability of ANPP across all sites. Importantly, nutrient effects at each site were inconsistent and were closely related with sites with initial richness and temperature seasonality. The structural equation modelling clarified that N and P addition alone mainly decreased community stability via decreasing dominant species stability. Notably, sites with higher species richness exhibited lower stability of dominant species and lower community stability under N or P enrichment. Taken together, our results highlight that effect of nutrient amendment on the stability of grassland ecosystems depends on local plant diversity shaped by specific climatic factors. This understanding is crucial for effective grasslands management in the context of global environmental change.