Nitrogen deposition changes the keystone taxa of soil microorganisms and indirectly affects plant aboveground biomass in desert steppe regions

Abstract Aims Nitrogen (N) deposition is an important component of global change and threatens terrestrial biodiversity. In past decades, the response of the relationship between plants and soil microbes to N deposition has attracted considerable attention. Keystone microbial taxa have been proven to provide nutrients for specific plant growth, especially in nutrient-poor desert steppe ecosystems. However, the effects of N deposition on plant and soil microbial community interactions in desert steppe regions remain poorly understood. Methods To investigate these effects, a six-year N-addition field experiment was conducted in a Stipa breviflora desert steppe in Inner Mongolia, Northwest China. Four N treatment levels (N0, N1, N2, and N3, corresponding to 0, 30, 50, and 100 kg N ha-1 yr-1, respectively) were applied to simulate atmospheric N deposition. Results The results showed that (1) after the six-year N deposition simulation, the plant aboveground biomass did not increase, but the plant community structure changed; (2) in desert steppes, the relationship between microorganism communities and Neopallasia pectinata was strengthened by N addition, while that between microorganism communities and S. breviflora was simplified; and (3) N deposition indirectly affected the plant biomass in desert grasslands, mainly along key-stone microbial taxa pathways. Conclusions Together, these results suggest that N deposition can alter plant community structures by affecting the relationships between plants and soil microorganisms in desert steppes. These findings contribute to a comprehensive understanding of the effects of atmospheric N deposition on the ecological health and function of desert steppes.