Structure Of Soil Microbial Community In The Rhizosphere Of Populus Euphratica In The Lower Reaches Of Tarim River And Its Correlation With Soil Physicochemical Properties

Populus euphratica Oliv.is the dominant constructive species of riparian forests in the lower reaches of Tarim River,which provides various ecological services including resource supply,climate regulation and water and soil conservation services.However,in recent years,the population structure of P.euphratica in the downstream region has always shown an inverted pyramid decline,and its living conditions are worrying.Rhizosphere area is the place where plant roots exchange energy and nutrients with soil.Rhizosphere microbial community is active in this region,which is closely related to plant growth and development.Studying the structure of plant rhizosphere microbial community is of great significance for improving plant stress resistance and disease resistance.In this study,P.euphratica at different growth stages(young,medium,overripe,and decline periods)in the lower reaches of the Tarim River was selected as the research object.On the basis,the physical and chemical properties of the rhizosphere soil were measured,and high-throughput sequencing technology and bioinformatics analysis method were used to analysis soil microbial community(bacteria and fungi).The community structure and diversity of relevant microbial communities in different growth stages of P.euphratica were comprehensively analyzed,as well as the correlation between them and soil physical and chemical properties,and the key influencing factors of microbial communities were discussed.The main research results were as follows:(1)A total of 7287 operational taxonomic units(OTUs)were obtained from the bacterial sequencing results of soil samples,and a total of 73 phyla,165 classes,339 orders,454 families,651 genera and 205species were obtained through comparison and identification.In addition,for the fungal sequencing results of soil samples,a total of 960 OTUs were obtained,and a total of 10 phyla,36 classes,77 orders,165families,275 genera and 353 species were obtained through comparison and identification.(2)The results of sequencing and analysis of bacteria in P.euphratica rhizosphere showed that:Proteobacteria,unidentified＿Bacteria and Halobacterota were the dominant phyla,while Marinobacter,Halomonas and Woeseia were the dominant genera.The richness and diversity of rhizosphere bacterial community showed a trend of first increase and then decrease with the growth period,and there was no significant difference between different growth periods.(3)The results of sequencing and analysis of fungi in P.euphratica rhizosphere showed that:Ascomycota and Basidiomycota were the dominant phyla,while Geopora,Chondrostereum and unidentified＿Sordariales＿sp were the dominant genera.There were no significant differences in the richness and diversity of rhizosphere fungal community among different growth stages,but there were significant differences in the composition of rhizosphere fungal community among medium and overripe,medium and decline periods(P<0.05).(4)The results of soil physical and chemical properties showed that some soil physical and chemical properties changed significantly with the growth period of P.euphratica,and the soil environment gradually became strongly alkaline.The available phosphorus,available potassium and total dissolved salts content reached the maximum in the rhizosphere of P.euphratica’s decline stage.(5)The results of correlation analysis between rhizosphere microbial community and environmental factors showed that soil water content,total potassium,total dissolved salts and p H were the environmental factors that significantly affected the composition of rhizosphere bacterial community(P<0.05).In addition,p H was the main factor driving the change of bacterial community of P.euphratica rhizosphere soil(r~2=0.678,P=0.001).(6)The results of correlation analysis between rhizosphere microbial community and environmental factors showed that total dissolved salt and total phosphorus were the environmental factors that significantly affected the composition of fungal community in rhizosphere of P.euphratica(P<0.05).In addition,total dissolved salt was the main factor driving the change of fungal community of P.euphratica rhizosphere soil(r~2=0.679,P=0.001).