Disentangling Effects of Moisture/gas Regimes on Microbial Community, Network Configuration and Nitrogen Turnover of Black Soil

Diverse microbes in arable black soil participate in the biogeochemical cycling of nitrogen, which profoundly impact on the fertility and greenhouse gas (GHG) emission. However, the effects of environmental factors on the structure and functions of microbial communities have not been thoroughly elucidated. We performed the indoor microcosm study to collect the soil samples under six moisture (constant and wetting)/gas (air, 10% acetylene, oxygen and argon) regimes and investigated the alterations of bacterial community composition, nitrification/denitrification gene abundance and nitrogen metabolic functions under different conditions by high-throughput sequencing, quantitative PCR, physicochemical analyses and bioinformatics. It was found that the N2O/CO2 emission under six moisture/gas regimes were significantly different (p < 0.001), the processing time also dramatically influenced the GHG emission, and there were considerable interactions between moisture/gas regime and processing time. The impact of moisture/gas regimes, processing time and interaction item on $${\text{NH}}_{4}^{ + }$$ -N and $${\text{NO}}_{3}^{ - }$$ -N was also conspicuous. The moisture/gas regime significantly affected the community diversity rather than community richness. The key responsive bacterial classes under different gas conditions were Gammaproteobacteria, Bacteroidia and Alphaproteobacteria, in contrast to Actinobacteria, Alphaproteobacteria and Thermoleophilia under different moisture regimes. The abundance of Piscinibacter, Chujaibacter, Symbiobacteraceae and Acidobacteriales species was positively correlated with moisture and N2O emission, and denitrification, nitrate reduction to ammonium, nitrification, nitrogen mineralization/fixation were the dominant processes of nitrogen cycle in black soil, which were supported by co-occurring network analyses and Spearman correlation heatmap. The hub nodes and connection mode of microbial nitrogen-cycling network differ under six moisture/gas regimes, and the same species could be active in multiple major nitrogen turnover processes simultaneously. These findings shed light on the prevention and control of soil fertility decline and global warming.