Soil Bacterial Co-occurrence Network In The Alpine Grassland Of The Qinghai-tibet Plateau

With changes in environmental factors such as precipitation patterns,climate,and changes in land use patterns,the grassland ecosystem on the Qinghai-Tibet Plateau has been severely damaged,and grassland degradation has become increasingly severe.Grassland degradation seriously affects the soil environment and plant diversity.As an important participant in the grassland ecosystem,soil microorganisms are also seriously affected by their diversity and the interrelationship between microorganisms.The composition,diversity,and interaction patterns of microbial community in grassland ecosystems have always been the focus of research.The study of soil microbes is helpful to understand grassland ecosystems,manage and restore grassland ecosystems.There are many studies on the composition,structure and diversity of soil microbial communities.A large number of studies mainly study the relationship between soil microbial diversity indicators and soil physical and chemical properties and plant diversity along environmental gradients,precipitation patterns and grazing patterns.In order to explore the correlation between soil bacteria and its influencing factors,this master thesis selected a plant species elimination experiment on the sunny slope of the gully plateau where the soil bacteria are rich,and set up seven blocks and eight treatments,which are control experiments.Removal of dominant species kobresia,removal of gramineae species,removal of two to three species per function group,removal of legumes,removal of rare species,removal of weeds,and all plant species removal experiments,analysis in the same habitat In the environment of different plant diversity(caused by plant species),the differences in soil bacterial co-occurrence networks and their possible causes;in addition,this master thesis is also investigating and studying different habitats(four sites)within the Qinghai-Tibet Plateau regional scale,at four sites along the environmental gradient(ditch bottom flat,sunny slope,mountain top and shady slope),the differences in soil bacterial co-occurrence networks in different habitats were compared and affected by environmental factors(soil environment,plant diversity).In each experimental plot,the differences between soil co-occurrence networks were compared using high-throughput sequencing technology and network analysis methods,and linear regression analysis was further used to explore the relationship between soil bacterial co-occurrence network differences and soil environment and plant diversity.In order to provide a theoretical basis for the protection and restoration of grassland ecosystems by analyzing the changes in the relationship between soil bacteria when they are affected by soil environment and plant diversity,and understanding the relationship between soil bacteria and soil and plant diversity.The results of the study found that in the plots where the control experiment,the dominant species kobresia was eliminated,the gramineae species were eliminated,and two or three species were eliminated from each functional group,the plant diversity was higher.The nature is similar,the dominant bacteria group is the same as the phytophthora,the negative correlation between soil bacteria is greater than the positive correlation;while in the elimination of legumes,rare species,weeds and all elimination experiments,the plant diversity is low,and the soil bacteria are Now the network structure is complex,the dominant bacteria are all bacteroides,the correlation between soil bacteria is significantly enhanced,and the positive correlation is greater than the negative correlation.The soil bacteria co-occurrence network differs greatly in different habitats,mainly manifested in the parameters of network topology properties,dominant bacteria groups and the correlation of soil bacteria.The specific performance is as follows: 1)The soil bacterial co-occurrence network structure in different habitats is quite different,and the topological property parameters are significantly different.For example,the soil bacterial co-occurrence network structure on yangpo is the most complicated,and the network on the flat ground is the simplest;2)Different habitats The dominant soil bacterial communities and their relative abundances in the soil bacterial co-occurrence network are also different;3)In the soil bacterial co-occurrence network of different habitats,the positive correlation between the soil bacteria in the shady slope is the strongest,and the negative correlation It has the weakest sex,the strongest negative correlation between soil bacteria and the lowest positive correlation between the soil bacteria on the flat bottom of the ditch.This correlation between bacteria has a significant correlation with soil physical and chemical properties.The positive correlation between soil bacteria has a significant positive correlation with the soil available nitrogen content,while there is a significant correlation with the available phosphorus,organic matter content and agrobacterium biomass negative correlation(P < 0.05),on the slopes with rich soil available nitrogen content,the positive correlation between soil bacteria is the strongest,while in the soil with available phosphorus,organic matter content and acidobacteria biomass more ditch bottom flat,The positive correlation between soil bacteria is the weakest.In the study of the same habitat,the influence of plant diversity on the soil bacterial co-occurrence network was not significant,and then the effects of plant diversity and soil environment on the cooccurrence network in different habitats were analyzed.This paper confirms from two experimental studies that the co-occurrence network between soil bacteria has a clear correlation with the soil environment,and is most closely related to soil available nitrogen,available phosphorus,and soil organic matter content.Habitat changes have a significant effect on the correlation of soil bacteria,and the plant diversity has no significant effect,because different habitats have not only differences in plant diversity,but also significant differences in soil environment.The soil bacterial network relationship may be mainly affected by the soil environment(nutrition,etc.),rather than directly affected by plant diversity.In environments with suitable habitats and high plant diversity,the bacterial network is simple and vice versa.