Nitrogen deposition decouples grassland plant community from soil bacterial and fungal communities along a precipitation gradient

Abstract

Plant–soil microbe interactions play a pivotal role in supporting plant health and growth, but it remains poorly understood how global change driving forces affect the associations between plants and microbial communities. Based on a 3-year (2019–2021) field experiment with changing precipitation and N addition manipulations in Inner Mongolia, we examined plant and soil microbial communities and their interactions under changing precipitation and N addition. Microbial community dissimilarities increased with increasing differences in soil moisture, regardless of N levels. Plant community significantly affected bacterial and fungal communities under ambient N only, but protistan communities under both ambient N and N addition. N addition reduced the slopes of microbial (bacterial and fungal, but not protistan) with plant community dissimilarities and the associations of their functional groups, which indicates a weakening relationship between soil microbiome and plant communities and their functional groups under N enrichment. Synthesis. Our results not only provide evidence on how atmospheric N deposition affects the interactions between plants and different microbial communities but also highlight the shift in plant–microbe relationships, especially the associations of plants with bacteria and fungi, but not protists, from coupling to decoupling due to N addition, which could have profound consequences on ecosystem functioning.