Distribution And Influencing Factors Of Soil Microbial Diversity In Agro-pastoral Ecotone Of Inner Mongolia

As the transitional zone between farming areas and grassland pastoral areas,the Agro-Pastoral Ecotone of Inner Mongolia has an important ecological and economic status,and its special climatic conditions and soil environment create the unique microbial community of the soil.Most of the previous studies are based on a single grassland or farmland ecosystem in Inner Mongolia,and there are few studies on the distribution of soil microbial communities after the long-term evolution of the two ecosystems.Therefore,in this study,we collected typical transect soils along the Hetao Plain to the northern foothills of Daxinganling,and used high-throughput sequencing technology to analyze the microbial community structure,diversity distribution and influencing factors of farmland and grassland soil under different ecological zones of Inner Mongolia.Further clarify the bacterial and fungal community structure and diversity distribution of soil in the Agro-Pastoral Ecotone of Inner Mongolia,and provide a reference basis for the improvement of soil quality and ecological environmental protection in the Agro-Pastoral Ecotone of Inner Mongolia from the perspective of soil microorganisms.The main findings show that:(1)The number of OTU of bacteria and fungi in grassland soil was higher than in farmland soil in most areas,and the number of OTU in wheat,rape,mung bean fields was lower.The number of fungal species in paddy field was higher than in dry field,and in Hetao plain the number of fungal species in wheat field was higher than in grassland and other farmland.(2)At the gate level of analysis,Actinobacteria(between 12.61-53.86),Proteobacteria(between 20.94-40.58),Acidobacteria(between 4.76-17.73)and Chloroflexi were the dominant bacteria phylum.The predominant fungi were Ascomycot,Mortierellomycota and Basidiomycota.The relative abundance of basidiomycota was48.12%(in hetao plain).The relative abundance of Morpitaria was 24.85%(in yanshan hilly region).Chytridomycota only exists in the farmland along the foothills of Daxinganling and loess Plateau.The total abundance of unknown bacteria in Hetao plain was 34.59%.(3)α diversity showed that soil bacteria richness was higher in the eastern and central regions,and the highest in the yanshan Hilly and Hetao plain regions.Soil fungal richness was the highest in Tumochuan plain,and grassland richness and diversity were higher in the foothills of Daxinganling,Xiliaohe Plain and Tumochuan plain.On the whole,microbe is scarce in farmland soil in western China.Soil β diversity showed that the soil bacterial community was localized,while the soil fungal community was relatively dispersed and was no significant difference in the variation rate between groups.(4)The precipitation in Inner Mongolia concentrated in the foothill of Daxinganling and Tumochuan plain,and the average annual temperature is higher in Xiliaohe plain,Loess plateau and Hetao plain.The farmland soil in Inner Mongolia was gradually salinized from east to west,and the grassland soil was acidic.The soil nutrient content was higher in grassland or dominant crop farmland in each region.Soil biological characteristics and soil nutrient changes were similar in each region.The contents of microbial biomass carbon and nitrogen in grassland soil were higher than those in farmland soil,and the activities of soil enzymes in the foothills of Daxinganling were higher than those in other regions.(5)Soil bacterial diversity rised perpendicularly with precipitation.The distribution of soil fungal diversity was affected by temperature easily,and decreased with the temperature increasing.Soil nutrients are closely related to soil enzyme activities,most physicochemical factors of pH,organic carbon,total nitrogen,nitrate nitrogen was significantly correlated with most biological trait of soil.pH,ammonium nitrogen,organic carbon is the main environmental factor affecting soil bacterial community in farmland and grassland.Proteobacteria was negatively correlated with Total potassium.Acidobacteria was correlated with AK.Actinobacteria was correlated with Nitrate nitrogen.pH,nitrate nitrogen,ammonium nitrogen is the main environmental factor affecting soil fungal community in farmland and grassland.Ascomycota was negatively correlated with nitrate nitrogen.Basidiomycota was positively correlated with Total phosphorus.And Mortierellomycota was negatively correlated with pH.