Local climate and biodiversity affect the stability of China's grasslands in response to drought.

The stability of ecosystems is of great significance to the supply of ecosystem services and human well-being. Frequently occurring drought events seriously threaten the stability of terrestrial ecosystems. In particular, in grasslands with low rainfall, ecosystems are more vulnerable to drought. To date, most studies have focused on forest ecosystems, while the difference in the stability of various types of grassland ecosystems under drought is less studied. Here, we selected China's grasslands as the study system and used the standardized precipitation evapotranspiration index (SPEI) to identify drought years and drought events (2001-2015) that occurred in China. Subsequently, we used the satellite-based enhanced vegetation index (EVI) to calculate the resistance (the ability to maintain the original EVI level in a drought year), resilience (the capacity of ecosystem functioning to recover to its normal state after a drought year), and recovery time (how long an ecosystem requires to recover to its predrought EVI) of different grassland types in China from 2001 to 2015. Finally, random forest analysis was used to identify the factors affecting the spatial patterns of the three indicators of stability. The results showed that the grassland ecosystem vulnerability to drought was significantly different among grassland types. The alpine steppe and alpine meadow ecosystems located on the Qinghai-Tibet Plateau have the strongest resistance, the weakest resilience, and the longest recovery time. The meadow steppe and typical steppe ecosystems located in Inner Mongolia have the weakest resistance, the strongest resilience, and the shortest recovery time. The stability of grassland ecosystems is mainly affected by the characteristics of drought events (drought severity and duration), local climate factors (precipitation and temperature), and biodiversity. These results provide a scientific basis for taking appropriate management measures to address the impacts of future drought events on various types of grassland ecosystems.