Soil Microbiota From Warmer and Drier Grasslands Are More Vulnerable to Drought Stress

The stability of soil microbial communities under drought stress is critical for sustaining ecosystem function in a changing climate. However, it remains unclear whether long-term exposure to arid environments strengthens microbial drought resistance through adaptation, or instead diminishes it by reducing diversity and shifting functional redundancy. To address this, we sampled soil microbiota (including bacteria, fungi, and protists) communities along a 3600-km aridity and temperature gradient in Chinese grasslands, and assessed their compositional resistance to experimental drought. We found that microbiota drought resistance decreased with increasing aridity and temperature, particularly for bacteria and protists. This reduced resistance was attributed to declines in taxonomic diversity, larger microbiota body size, and compositional shifts toward oligotrophic taxa in drier regions. These findings suggest that structural shifts in soil communities associated with chronic arid climate may heighten vulnerability to acute drought events, potentially eroding ecosystem resistance as future climate extremes intensify.