Spatial Distribution Characteristics Of Soil Nutrients And Bacterial Community Structure In Road Greenbelt Within 5th Ring Road Of Beijing City

The urban road greenbelt soil within 5th ring road in Beijing was selected as the subject,using GIS and geostatistics methods to investigate the spatial distribution of soil nutrients and bacterial community structure.The diversity,community composition and relative abundance of soil bacteria communities were studied through Illumina Miseq,which can accurately reflect the current stability of soil ecosystem and provide an important reference for the management of urban road green belt.The main conclusions were as follows:(1)The average contents of soil organic matter,total nitrogen,alkali-hydrolyzed nitrogen,available phosphorus and available potassium were 14.25 g·kg-1,0.65 g·kg-1,54.17 mg·kg-1,18.69 mg·kg-1 and 177.95 mg·kg-1,respectively.According to the classification standard of soil nutrients in Beijing,the soil nutrient status of road greenbelt in the 5th ring road of Beijing is generally in the lower middle level,but the content of available potassium is higher.The variation coefficient of 5 soil nutrients was between 40.00%?56.10%,showing moderate variability.(2)Semi-variance analysis indicated that organic matter,alkali-hydrolyzed nitrogen and available potassium are based on exponential models,and total nitrogen and available phosphorus are spherical models.In addition,the nugget coefficients of organic matter,total nitrogen and available phosphorus are all more than 75%,which belonged to weak spatial correlation;The nugget coefficients of alkali hydrolyzed nitrogen and available potassium are more than 25%,less than 75%,showing moderate spatial correlation.The distribution characteristics of soil nutrients are obtained through spatial interpolation analysis in the study area,the content of organic matter decreases from northwest to southeast,all below level III.The nitrogen content reaches level IV to V in the whole region,while available potassium and phosphorus are relatively abundant.(3)The results showed that the soil bacterial community diversity and richness are significantly different within Beijing 5th ring road greenbelt,and there is a downward trend from the city center to external area.The predominant bacterial groups were Proteobacteria,Actinobacteria,Acidobacteria and Bacteroidetes,accounting for 78%of the total soil bacteria.The dominant bacterial genus were RB41,Sphingomonas and H16.(4)By fitting semi variant function,Shannon and Simpson are Gauss model.Ace was exponential model,and Chaol was spherical model;The nugget coefficients of 4 exponent are all over 75%,which belonged to weak spatial correlation,showing that the soil bacterial community structure in the study area was mainly affected by artificial random elements.The distribution characteristics of soil nutrients are obtained through spatial interpolation analysis in the study area.It suggested that Shannon and Simpson decreased stepwise from the center to the outside,Ace and Chaol showed a trend that the highest were in the center and southeast,followed by the East and the lowest in the west.(5)The community structure of bacteria at genus level is more distinct than phylum level.In addition,the redundancy analysis(RDA)of soil bacterial community structure and soil variables explain a total of 50.26%of the variance,suggesting that soil water content,total nitrogen,soil organic carbon and available nitrogen were the key factors which significant influenced the bacterial community structure.We conclude that the nutrient status of the urban road greenbelt soil within 5th Ring in Beijing is generally at the lower-middle level,improving the maintenance and management of road greenbelt could upgrade the level of soil quality,thereby optimizing soil bacterial community structure and promoting the stability of soil ecosystem.