Study On The Changes Of Soil Microorganisms During The Succession In Daihai Lakeside Wetland

Daihai Lake and its watershed located in the ecotone between agriculture and animal husbandry in Inner Mongolia,which are the key strategic nodes of ecological barrier construction in the north of China.In recent years,because human activities and global climate change,the lakeside vegetation in this area has undergone a series change of succession.The soil microbial community plays an important role in the material circulation and energy flow of the whole ecosystem.Especially the response of its community composition and diversity changes to vegetation succession and environmental factors has received little attention.In this paper,the wetland in the lakeside zone of Daihai Lake is served as the research object.Combined with plant community composition and soil salinity gradient,the vegetation succession sequence in the study area is determined to be four types: heavily salinized bare land(HM),salinized meadow(SM),slightly salinized meadow(SS)and wet meadow(WM).Based on the investigation of plant community information,the physical and chemical properties of soil were measured and the composition of soil microbial community was measured by high-throughput sequencing technology.Then the distribution pattern of soil bacteria and fungi communities in different depths with salinity gradient and the dynamic changes of key species and their main driving factors were discussed.The research results showed that:(1)Along with the successional direction,the species diversity of wetland plants in daihai lakeside zone gradually increased,and the wet meadow with basic soil desalination reached the maximum at the end of succession,which showed as heavily salinized bare land < salinized meadow < slightly salinized meadow < wet meadow.On the whole,the richness and diversity of soil bacteria and fungi communities in Daihai lakeside wetland show the same change rule with aboveground plants.This result shows that ecosystem was limited by salt in the wetland,which the distribution pattern of soil microorganisms are similar to that of vegetation species diversity.(2)The composition of soil microbial community is a significant difference with different soil salinity in the wetland of the Daihai Lakeside.Soil bacterial community:Proteobacteria is the dominant phyla in the study area.Actinobacteria and Acidobacteria have relatively high relative abundant in the slightly salinized meadow and wet meadow soil.However,Bacteroidetes,Firmicutes and Campilobacterota have relatively higher abundant in the soils of heavily salinized bare land and salinized meadows.Soil fungal community: Unclassified?k?Fungi phylum is the dominant phyla in heavily salinized bare land and salinized meadow soil.Ascomycota is the dominant phyla in slightly salinized meadow and wet meadow soil.Basidiomycota,Glomeromycota and Blastocladiomycota are relatively abundant in slightly salinized meadow and wet meadow soil.The Rozellomycota is higher relative abundance in heavily salinized bare land and salinized meadow soil.(3)According to Wilcoxon rank-sum test,there are significant differences in the Shannon index,Simpson index,ACE index and Chao1 index of soil microorganisms at different succession stages.Under the same salinity gradient,the composition of soil bacteria and fungi have no significant difference among different soil layers,but some bacterial species will change their abundance as the depth of the soil layer changes.The results of ? diversity also showed that bacterial and fungal communities were clustered in the same succession stage,which further proved that there were significant differences in soil bacterial and fungal community structures in different succession stages.(4)In surface of soil,soil properties are the direct driving factors of microbial community and the soil salinity is most important of factors.With deeping of the soil depth,the influence of plants for microorganisms was increased.Structural equation model analysis shows that soil salinity and soil moisture are the key driving factors affecting the distribution pattern of soil microbial community in Daihai lakeside wetland.They can regulate soil microbial community indirectly through regulating the plants and soil nutrients directly.From the perspective of plant-soil-microorganism,the changes of soil microorganisms under the succession of wetland vegetation were discussed.The research results have certain theoretical significance and application value for the evaluation of microbial resources in wetland ecosystem and the restoration and reconstruction of degraded wetland ecosystem.