Aridity determines the effects of warming on community stability in Inner Mongolian grassland

Ongoing climate warming affects biodiversity and ecosystem functions and services. However, the mechanisms underlying the effects of climate warming on biodiversity-stability relationships are unclear. Whether these effects depend on environmental factors such as aridity remains an open question. Here, we conducted a factorial field experiment to investigate the effects of warming on nine grasslands in a transect spanning ∼1500 km with increasing aridity in Inner Mongolia, China. Our results showed that warming-induced decrease in species richness did not alter community variability across nine grasslands. However, species richness was negatively related to community variability under warming conditions, but not under control conditions. This indicated that warming regulated the species diversity-stability relationship. Warming increased species synchrony, species variability, and dominant species variability. These outcomes lead to increases in temporal variability of community productivity. Climate fluctuation increased species variability and species synchrony within communities, thereby reducing community stability. Importantly, the size of warming effects on community variability via biotic mechanisms grew with increasing aridity. Our results indicate that species diversity plays a crucial role in regulating community stability under climate warming. Our findings reveal the generality of biotic mechanisms responsible for grassland stability under future climate warming, and highlight that the geographic variation in aridity determines the effect sizes of warming on grassland stability. We suggest that ongoing and future climate warming might disrupt grasslands stability with high aridity, thereby reducing ecosystem functions and services.