Response of Soil Bacteria to Short-Term Nitrogen Addition in Nutrient-Poor Areas

Increasing nitrogen (N) addition induces soil nutrient imbalances and is recognized as a major regulator of soil microbial communities. However, how soil bacterial abundance, diversity, and community composition respond to exogenous N addition in nutrient-poor and generally N-limited regions remains understudied. In this study, we investigated the effects of short-term exogenous N additions on soil bacterial communities using quantitative polymerase chain reaction (PCR) and Illumina Miseq sequencing in an in situ N addition field experiment. The results showed that a low nitrogen addition increased the observed species (Sobs) of the bacterial community, and with the increased nitrogen addition, the Sobs of bacteria gradually decreased, especially the unique OTUs. The relative abundance of Proteobacteria, Actinobacteria, and Gemmatimonadetes increased with increasing nitrogen addition, whereas the relative abundance of Chloroflexi and Firmicutes decreased. Soil properties play an important role in bacterial community structure at phylum or genus levels. Short-term nitrogen addition increased the proportion of nodes from Actinobacteria and Proteobacteria in the co-occurrence network and enhanced the stability of the microbial network. Actinobacteria may play an important role in constructing the network. Our study aims to explore the effects of nitrogen addition on the diversity, composition, and structure of soil bacterial communities in nutrient-poor areas caused by ecological disturbances.