Study On Rhizosphere Soil Nutrients And Microorganisms Of Cleistogenes Songoria In Desert Grassland Under Different Stocking Rates

Desert steppe is an unique ecosystem of Eurasia which has the characteristic of most arid but least productivity.Grazing is the most direct,economical and almost the only utilization way for Desert steppe.Stocking rate is the determining factor that affects the productivity,community structure and function of grassland ecosystem.Rhizosphere is the interface of substance exchange and energy flow in plant root-soil-microbial system,which has an important effect on the dynamic of ecosystem nutrients distribution.However,there are few reports about the effects of stocking rate on rhizosphere soil nutrient.Taking the Cleistogenes songoria,a dominant species of Desert steppe,as the object and relying on a long term sheep grazing experiment platform which established in 2004 and including four stocking rate(no grazing,CK;Light grazing,LG;Moderate grazing,MG and Heavy grazing,HG),this research studied the effects of stocking on physical and chemical properties as well as microbial community of Cleistogenes songoria thizosphere and non-rhizosphere soil.Simultaneously,we analyzed the relationship between soil environmental factors and microbial community.The aim of this study was to figure out the nutrient difference between rhizosphere and non-rhizosphere soil,and reveal the adaptation strategies and involved mechanisms of Desert steppe species to nutrients poverty and drought.The results of this study could provide a theoretical basis for rational utilization of grassland.The main findings are follows:(1)Grazing significantly increased Cleistoneges songoria rhizosphere and non-rhizosphere soil nutrients.Soil pH,water content and total nitrogen of rhizosphere soil were lower than that of non-rhizosphere soil in all the stocking rate(P<0.05),but no difference were found between rhizosphere and non-rhizosphere for ammonium nitrogen,available phosphorus,total carbon and total phosphorus and C/N(P>0.05);rhizosphere soil has lower C/P and N/P than that of non-rhizosphere soil in MG and HG.(2)Grazing had no significant effects on Cleistoneges songoria microbial community structure for both rhizosphere and non-rhizosphere soil(P>0.05),but significantly changed the relative abundance of major microbiota groups(P<0.05).Grazing significantly reduced the diversity of soil bacterial communities for both rhizosphere and non-rhizosphere soil(P<0.05),but had no significant effects on the diversity of soil fungal communities(P>0.05).The diversity of microbial and fungal communities in rhizosphere soil was significantly lower than that in non-rhizosphere soil(P<0.05).(3)Soil microbial diversity and major microbial groups were significantly correlated with soil nutrient content(P<0.05).Ammonium nitrogen and nitrate nitrogen are the key factors that regulate the bacterial and fungal communities in the rhizosphere soil of Cleistogenes songoria(P<0.05),total carbon,total nitrogen,ammonium nitrogen,nitrate nitrogen,and carbon/nitrogen/phosphorus values showed significant influence on bacterial community of non-rhizosphere soil of Cleistogenes songoria(P<0.05),the change of soil physical and chemical properties had no significant effect on the fungal community of non-rhizosphere soil of Cleistogenes songoria(P>0.05).