| Soil bacteria are an important part of the soil ecosystem and play a vital role in the material cycle and energy flow of the earth’s ecosystem.As a kind of microbial interaction,microbial antagonism has important effects on the structure and function of soil bacterial community.Streptomyces widely exists in soil and can produce a variety of antagonistic compounds,it is an important contributor to the antagonism of soil microorganisms.There are many factors affecting soil microbial antagonism and community structure,among which climate warming and plant community changes are the current research highlights.There are many studies focused on the short-term effects of dominant plant or warming on soil microorganisms,but few studies focus on their interaction effects on soil bacterial antagonism and community structure,especially in the long-term observation.This study was conducted at the Gansu Gannan Grassland Ecosystem National Field Scientific Observation and Research Station in Maqu County,eastern Qinghai-Tibet Plateau.The soil bacterial community was taken as the research object.The aboveground part of dominant shrub Dasiphora fruticosa was removed for a long time,and open top chamber was used to simulate warming,then a four-year control experiment was conducted.We did aboveground plant community quadratic survey,soil physical and chemical properties determination,soil Streptomyces culture,quantitative polymerase chain reaction and high-throughput sequencing of soil bacteria.Two-way analysis of variance was conducted to study the effects of shrub,warming and their interaction on aboveground plant Shannon diversity and biomass,soil physical and chemical properties,Streptomyces antagonism and soil bacterial Shannon diversity and biomass.Nonmetric multidimensional scaling analysis was adopted to explore the differences of plant community composition and soil bacterial community composition among different treatments.Spearman correlation analysis,mantel test and redundancy analysis was applied to explore the relationship between aboveground plant community,soil physical and chemical properties,soil Streptomyces antagonism and soil bacterial community.Results are as follows:1)Shrub removal significantly decreased the content of soil organic carbon,total phosphorus and carbon to nitrogen ratio,but increased the content of soil ammonium.Warming significantly reduced the content of soil total phosphorus.The interaction of shrub removal and warming showed no significant effects on all soil physical and chemical properties.Both shrub and warming significantly affected the composition of aboveground plant community,and significantly decreased the Shannon diversity and biomass of aboveground plant community.The interaction of shrub and warming significantly impacted plant biomass,but had no significant effect on plant community composition.2)Shrub removal significantly decreased soil total Streptomyces density and significantly increased the proportion of antagonistic Streptomyces.Warming and the interaction with shrub did not significantly affect four indices of Streptomyces antagonism.In addition,the total Streptomyces density was significant positively correlated with soil carbon to nitrogen ratio and negatively correlated with plant community Shannon diversity and biomass;inhibition zone size was positively correlated with soil total phosphorus;the proportion of antagonistic Streptomyces was positively correlated with plant community biomass.Mantel test showed that there was a significant correlation between aboveground plant community composition and Streptomyces antagonism.3)Warming significantly decreased bacterial Shannon diversity.Warming significantly increased soil bacterial biomass,and the interaction of shrub removal and warming significantly affected bacterial biomass,in the no warming condition,shrub removal increased bacterial biomass,while shrub removal decreased bacterial biomass in the warming condition.Both warming and shrub removal significantly affected bacterial community composition.The interaction of warming and shrub removal did not significantly affect soil bacterial Shannon diversity and community composition.Soil bacterial Shannon diversity has marginally and significant positively relationship with soil p H and total phosphorus,soil physical and chemical properties,plant community Shannon diversity and Streptomyces antagonism were not significantly correlated with bacterial biomass.Proteobacteria,Actinobacteria and Acidobacteria was the dominant phyla under the treatments.Shrub significantly increased the relative abundance of Proteobacteria and significantly decreased the relative abundance of Acidobacteriota.Warming significantly increased the relative abundance of Actinobacteria and significantly decreased the relative abundance of Acidobacteriota.The relative abundance of Proteobacteria was significant positively correlated with soil p H and soil water content;the relative abundance of Actinobacteria was significant negatively correlated with plant Shannon diversity;the relative abundance of Acidobacteria was significant positively correlated with plant Shannon diversity.Our results showed that the long-term removal of shrub significantly affected soil Streptomyces antagonism,and soil Streptomyces antagonism was mainly regulated by plant community.Long-term warming inhibited soil bacterial Shannon diversity and reversed the negative effect of shrubs on soil bacterial biomass.Soil bacterial community composition was significantly affected by both long-term removal of shrub and simulated warming,which may be regulated by soil physical and chemical properties.This study aims to reveal the effects and mechanism of long-term shrub removal and simulated warming and their interaction on soil bacterial antagonism and community structure in alpine meadow,it is helpful for further understanding the driving factors of soil microbial community changes in alpine meadow under global warming context,and for maintaining ecosystem stability in alpine meadow. |
