Spatial-Temporal Distribution Of Carbon And Nitrogen Cycle Microorganisms In Coastal Wetlands And Its Influencing Mechanism On Carbon Emissions

Affected by hydrology,topography,vegetation,soil nutrient matrix and physical,and chemical properties,the soil microbial community in coastal wetland of Yellow River Delta has obvious spatial and temporal distribution characteristics.As coastal wetlands are important sources of greenhouse gas emissions,studying the carbon emission mechanisms of soil microorganisms can provide a microbiological basis for wetland carbon reduction and mitigation of the global greenhouse effect.In this paper,soil samples were collected from 10-60 cm depth in spring and autumn from typical mudflats,Suaeda salsa and Phragmites australis samples in the Yellow River Delta.The effects of vegetation differences on the community structure of nitrogen-fixing microorganisms and N-DAMO bacteria in coastal wetlands were investigated using 16S r RNA and high-throughput sequencing of macro genes.This study provides a scientific basis for the biogeochemistry,vegetation restoration and sustainable development of coastal wetlands in the Yellow River Delta.It is of theoretical and practical significance to investigate the mechanism of salinization on the distribution pattern of vegetation in the coastal wetlands of the Yellow River Delta and to reveal the interaction between vegetation,soil microbial carbon and nitrogen cycles,and community structure diversity.The results of the study indicate that:1)The spatial and temporal distribution characteristics of microorganisms showed that changes in microbial activity not only regulated the vertical distribution of plant root secretions between roots through catabolic metabolism,but also influenced the different accumulation of microbial residues at different soil depths through anabolic processes.2)The abundance of genes associated with the citric acid cycle（7627 OTUs）,carbon fixation by prokaryotes（4691 OTUs）,glycolysis and glycogenesis（8218 OTUs）,and glyoxylate and dicarboxylic acid metabolism（8844 OTUs）in the carbon cycle was high.3)Soil microorganisms in the coastal wetlands of the Yellow River Delta showed large spatial and temporal variability among sites.The dominant species in the microbial community were largely similar at each taxonomic level,but the relative abundance of soil bacteria differed among vegetation cover.Among them,the microbial diversity and total amount in the reed sample site were higher than those in the alkali poncho area,and the differences in dominant species were obvious.4)The main environmental factors affecting the microbial community structure of wetland soil carbon and nitrogen functions were salinity,NO₃^-,TP,Na⁺,and p H.SO₄^2-was positively correlated with bacteria involved in the sulfur cycle.Higher ORP was significantly negatively correlated with the rate of N-DAMO（P<0.05）.Salinity,NO₃^-and NO₂^-concentrations were important environmental factors affecting the N-DAMO process in wetland soils.5)Methylacidiphilaceae,Beijerinckiaceae and Azospirillum（P=0.034）,three bacterial species,were the main microbial taxa affecting soil CH₄emissions in the study area of this paper,and when their abundance increased,CH₄emissions increased.