Soil microbial responses to large changes in precipitation with nitrogen deposition in an arid ecosystem.

Climatic change severely affects terrestrial ecosystem functioning by modifying soil microbial communities, especially in arid ecosystems. However, how precipitation patterns affect soil microbes and the underlying mechanisms remain largely unclear, particularly under long-term dry-wet cycling and vice versa in field settings. In this study, a field experiment was conducted to quantify soil microbial responses and resilience to precipitation changes with nitrogen addition. We established five levels of precipitation with nitrogen addition over the first 3 years and then balanced this with compensatory precipitation in the fourth year (i.e., reversed the precipitation treatments), to recover to the levels expected over 4 years in a desert steppe ecosystem. Soil microbial community biomass increased with increasing precipitation, and the reversed precipitation reversed these responses. The soil microbial response ratio was constrained by the initial reduction in precipitation, whereas the resilience and limitation/promotion index of most microbial groups tended to increase. Nitrogen addition reduced the response rates of most microbial groups, depending on the soil depth. The soil microbial response and limitation/promotion index could be distinguished by antecedent soil features. The precipitation regime can regulate the responses of soil microbial communities to climatic change via two potential mechanisms: (1) concurrent nitrogen deposition and (2) soil chemical and biological mediation. Soil microbial behaviors and their associations with soil properties should be considered when assessing the responses of terrestrial ecosystems to climatic change.