Effects of nitrogen deposition on microbial communities in grassland ecosystems: Pronounced responses of archaea.

Nitrogen deposition is a crucial component of the global nitrogen cycle and a significant driver of global change. However, current research remains relatively limited regarding the effects of nitrogen deposition on soil properties and microbial communities in grassland ecosystems following long-term natural recovery. Therefore, a simulated nitrogen deposition experiment was conducted in Yunwu Mountain to explore the effects of nitrogen deposition on soil properties and microbial communities. The results showed that nitrogen deposition significantly increased the content of ammonium nitrogen and nitrate nitrogen. Meanwhile, the release of protons caused by the increase in ammonium nitrogen led to a significant decrease in soil pH. Regarding microbial communities, bacterial and fungal communities showed no significant response to nitrogen deposition, whereas archaeal communities were significantly affected. Nitrogen deposition reduced migratory capacity of archaea between the rhizosphere and endosphere, resulting in a significant reduction in the diversity of endophytic archaea. Co-occurrence network analysis demonstrated severe disruption of archaeal network structures under nitrogen deposition. Furthermore, null model analysis revealed that nitrogen deposition altered the community assembly processes of endophytic archaea, driving a gradual shift toward deterministic processes. The results of this study provide key evidence for understanding the ecological hazards of nitrogen deposition and emphasize the need to pay special attention to changes in archaea when studying the long-term effects of nitrogen deposition on ecosystems.