Effects And Mechanisms Of Dominant Shrub Dasiphora Fruticosa On Soil Bacterial Antagonism And Community Structure In Alpine Meadow

Soil microorganisms,an important part of the underground biome,participate in ecological processes such as material cycling and energy flow directly or indirectly.As an important component of soil microbial diversity,bacterial communities play an important role in maintaining soil ecosystem functions.Plants are broadly perceived to influence soil bacterial community through litter,secondary metabolites,and inducing changes in soil environment and nutrient level.Therefore,plants are considered to be an important factor affecting soil bacterial communities.Microbial antagonism refers to the phenomenon that microorganisms inhibit the growth of other strains by producing antagonistic compounds.Microbial antagonism is a common interaction in microbial communities,which is critical to microbial community structure and helps maintain microbial diversity.Streptomyces,one of the major taxa of soil bacterial community,widely exists and produces a variety of antagonistic compounds in soil.Therefore,Streptomyces is widely used to study the soil microbial antagonism.However,when exploring the mechanism of plant species effects on soil bacterial community,most studies only pay attention to the role of plant community composition and soil physiochemical properties,but ignore the importance of microbial antagonism.In particular,how soil Streptomyces antagonism mediates the effects of above-ground plant species on soil bacterial communities.In this study,we selected a dominant shrub Dasiphora fruticosa as our research object in alpine meadow area of Qinghai-Tibet Plateau,and selected five experimental plots(Nangqian,Chengduo,Xinghai,Tianzhu,Subei)to sample.We used a cultivation-based approach to characterize the soil Streptomyces antagonism,while the community structure of soil bacteria was measured by high-throughput sequencing technology.Meanwhile,combined with the data of plant survey and soil physiochemical properties to explore the effects and mechanisms of dominant shrub Dasiphora fruticosa on soil bacterial antagonism and community structure.The linear mixed-effect model was used to analyze the effects of Dasiphora fruticosa on plant richness and biomass,soil physiochemical properties,soil Streptomyces antagonism and community diversity of soil bacteria.In addition,the effects of Dasiphora fruticosa on community composition of plant and soil bacteria were analyzed by nonmetric multidimensional scaling.Finally,the relationships between soil bacterial community,plant community,soil physiochemical properties and soil Streptomyces antagonism were analyzed through Spearman correlation analysis,redundancy analysis,ordinary least squares regression and mantel test.The results are as follows:1.The presence of Dasiphora fruticosa significantly reduced the plant richness,but had no significant effect on plant biomass.Meanwhile,the presence of Dasiphora fruticosa significantly affected the composition of plant community,which was mainly caused by Euphorbia pekinensis,Gentiana macrophylla,Polygonum macrophyllum and Carex atrata.2.The presence of Dasiphora fruticosa significantly increased soil p H,electrical conductivity,soil organic carbon and nitrate,but significantly reduced soil total nitrogen,while soil water content and ammonium as well as total phosphorus were not significantly affected by Dasiphora fruticosa.3.The presence of Dasiphora fruticosa significantly increased the antagonistic Streptomyces density and proportion of antagonists,and had a marginally significant effect on total Streptomyces density,but had no significant effect on inhibition zone size.The results of correlation analysis between soil Streptomyces antagonism,plant community and soil physiochemical properties showed that there was a significant relationship between plant community composition and soil Streptomyces antagonism.Meanwhile,total Streptomyces density was significantly related to soil p H,electrical conductivity,nitrate content,total nitrogen content,total phosphorus content as well as soil organic carbon content,and there was a significant correlation between antagonistic Streptomyces density and total phosphorus content.In addition,there was a significant correlation between proportion of antagonists,soil p H,ammonium content and total nitrogen content.These results indicated that Dasiphora fruticosa may affect the soil Streptomyces antagonism through plant community and soil physiochemical properties.4.The presence of Dasiphora fruticosa significantly increased the soil bacterial diversity,and significantly affected the community composition of soil bacteria.There was a significant correlation between plant community composition and bacterial community composition,and Dasiphora fruticosa had a significant impact on plant community composition,which indicated that Dasiphora fruticosa may affect soil bacterial community through plant community.At the same time,Dasiphora fruticosa may affect the soil bacterial community through soil physiochemical properties,and soil p H,electrical conductivity,total nitrogen and soil organic carbon were the main soil physiochemical indices affecting the bacterial community.In addition,there was a significant correlation between antagonistic Streptomyces density and soil bacterial diversity,and the results of redundancy analysis also showed that the antagonistic Streptomyces density and proportion of antagonists were significantly correlated with the relative abundance of soil bacterial groups,which indicated that Dasiphora fruticosa may affect the soil bacterial community through soil Streptomyces antagonism.In conclusion,our study showed that dominant shrub Dasiphora fruticosa had significant effects on soil Streptomyces antagonism,and these effects were closely related to the plant community and soil physiochemical properties.At the same time,Dasiphora fruticosa had a significant effect on community structure of soil bacteria,and soil Streptomyces antagonism played an important role in this process.This study further revealed the mechanism of dominant shrub Dasiphora fruticosa effects on soil bacterial community in alpine meadow,and emphasized the important role of microbial antagonism in mediating the effects of plant species on soil microbial community,which will help us to better understand the mechanism of plant species effects on soil microbial community.What’s more,it will provide a theoretical basis for the protection of soil microbial diversity in alpine meadow ecosystem.