The Diversity And Function Of Rhizosphere Microorganisms Of Typical Coastal Wetland Vegetation In China

As a unique and fragile ecosystem,coastal wetlands play a vital role in the global biogeochemistry cycle.In recent years,with the prevalence of global blue carbon research,the ecological processes and functions of typical vegetation communities in coastal wetlands have received increasing attention from the academic community.However,the community ecology of rhizosphere microorganisms in coastal wetlands needs further improvement.To reveal the basic characteristics of rhizosphere microbial composition in typical vegetation communities of coastal wetlands in China and evaluate the differences in community structure caused by human interference,we conducted an investigation.This study conducted field sampling and community quadrat surveys with the typical coastal wetland vegetation community types in northern and southern China,"Liaohekou Suaeda and Phragmites communities"and"Dongzhaigang mangrove community",as the research objects,High throughput sequencing technology was used to study the diversity and function of rhizosphere microbial communities in coastal wetlands,as well as their relationships with soil physical and chemical factors,heavy metals,and other factors.Furthermore,the structural differences of rhizosphere microbial communities in coastal wetlands caused by human interference were further analyzed.The main research contents of the thesis are as follows:（1）The results of research on rhizosphere soil samples from seven types of sample plots in the Liaohe Estuary show that soil physical and chemical characteristics are less affected by differences in coverage,but more significantly affected by vegetation types.The physical and chemical properties of rhizosphere soil with wetland characteristics are significantly different from those in artificial habitats.The PCo A and NMDS results This indicates that compared to the two types of artificial environments,the composition of rhizosphere bacterial community structure of wetland vegetation is more similar,but there are also certain differences in different vegetation types and coverage.Proteobacteria is the dominant phylum among all soil types,but the relative abundance ratio is higher in Suaeda and Phragmites communities;Gillisia and Woeseia are the two most dominant genera in Suaeda and Phragmites communities,but these genera have extremely low abundance in farmland and aquaculture ponds.As and Ni are the main heavy metal factors affecting bacterial communities,while NO₃^--N is the controlling factor for the composition of community structure in nutrients.Analysis of the FAXPROTAX database indicates that chemical heterotrophic functions dominate.The cycle of sulfur and nitrogen is significantly influenced by vegetation type and coverage;Compared to wetland characteristic vegetation,the autotrophic ability,nitrogen absorption and transformation function,and complex organic pollutant degradation ability of soil bacterial communities within the artificial habitat show poor levels.（2）The results of three types of rhizosphere soil samples from Dongzhaigang Mangrove Wetland show that in terms of soil physical and chemical properties,the rhizosphere soil of original mangrove vegetation is richer in TOC accumulation and higher in total nitrogen and nitrate nitrogen content than that of artificial restored vegetation and bare land.In terms of bacterial communities,the Alpha diversity results show that original vegetation has higher species diversity abundance,while the Beta diversity analysis shows that the three types of samples are significantly separated,and the two types of mangrove vegetation are significantly different from the bare land.The dominant phylum of rhizosphere bacterial community is Proteobacteria,which contains the genera Pseudomonas,which is the dominant genus in wetland rhizosphere soil.RDA analysis showed that among non heavy metal factors,TN and TOC had a significant impact on the aggregation of bacterial communities;As,Pb,and Cr are the main heavy metal control factors in the community.Based on PICRUSt2 analysis,it was found that in terms of gene abundance for nitrogen absorption,fixation,and transformation functions,restored mangrove>original mangrove>bare land.In terms of fungal communities,the results of PCo A showed that there were significant differences in the rhizosphere fungal community structure between bare land samples and in situ vegetation samples.In terms of community composition,Ascomycota and Plectosphaerella have absolute advantages at the phylum and genera levels,respectively.According to the annotation results of FUNGuild database,two main functional types of fungal communities were obtained,namely,plant pathogenic fungi and soil saprophytic fungi.The relative abundance of soil saprophytic fungi that reflect the productivity and stability of community ecosystems in the three types of samples is ranked as follows:original mangrove>restored mangrove>bare land.（3）In the two typical types of wetlands in the north and south,although the vegetation types are completely different,the main bacterial flora of the rhizosphere bacterial community is Proteobacteria,which is the core rhizosphere bacterial flora of characteristic vegetation in various coastal wetlands,and is the main contributor to the material cycle and pollutant purification capacity of coastal wetlands.Woeseia is only found in root samples of various wetland characteristic vegetation.The destructive interference to coastal wetlands（reclamation of farmland and aquaculture ponds）leads to significant differences in the composition and abundance of bacterial communities compared to native vegetation.Some bacterial species with the ability to metabolize nitrogen and sulfur and degrade complex organic pollutants will decrease or even disappear,resulting in the destruction of the overall self-repairing and regulatory capacity of the wetland;Under the artificial impact of remediation（artificial replanting of mangrove vegetation）,the content of nitrite nitrogen in the rhizosphere soil is significantly lower than that of bare land soil without vegetation cover,and has higher ecosystem productivity and stability.The composition and abundance of bacterial and fungal communities are closer to the original biological communities of the wetland,and the repaired vegetation even has stronger nitrogen metabolism ability and richer gene expression of nitrogen absorption and transformation related enzymes than in original mangrove vegetation.This study evaluated the composition and diversity of rhizosphere microbial structure of typical coastal wetland vegetation in China,revealing that human activity interference has a significant impact on the microbial ecology of coastal wetland soil.The research results provide scientific guidance and suggestions for the ecological restoration project of China’s"Southern Red and Northern Willow"coastal wetland,the construction of coastal wetland parks,and the development of"Blue Carbon"related work from a microbial perspective.