Differences And Influencing Factors Of PLFA Fingerprints Under Different Land Use Patterns In Red Soil

Reasonable land use is very necessary for improving soil quality and realizing the sustainable use of land resources.In this study,four locations of Qiyang(QY)in Hunan Province,Jinxian(JX)in Jiangxi Province,Minhou(MH)in Fujian Province and Guangzhou(GZ)in Guangdong Province were selected.Four types of soil were used as the research object,which were dryland and paddy field with conventional fertilization in the field ecosystem and woodland and abandoned land in the natural ecosystem around the long-term location test stations.By measuring soil p H,organic matter,nitrogen,phosphorus,potassium and other nutrients,the characteristics of basic physical and chemical properties of red soil under different land use patterns were analyzed.The microbial community structure and microbial entropy characteristics of red soil were analyzed by measuring soil microbial phospholipid fatty acids,the activities of extracellular enzymes and microbial biomass.The main controlling factors of microbial community structure and microbial entropy in red soil were identified by statistical analysis methods such as redundancy analysis and random forest.The main findings are as follows:(1)There were significant differences in soil physical and chemical properties under different land use patterns.Soil p H varied widely(4.16～6.90).Forestland soil showed low p H in the four sites,and the acidification problem was serious.Among the total nutrients,soil organic carbon(SOC)and total nitrogen(TN)contents had similar variation characteristics.In addition,the soil carbon,nitrogen and phosphorus contents in forestland were generally the lowest among the four points,while paddy field had significant advantages in the contents of carbon,nitrogen and phosphorus,and dry land had higher contents of phosphorus.The soil of paddy field in Qiyang had an obvious SOC advantage,but the content of soil dissolved organic carbon(DOC)had no similar expression.On the contrary,the Minhou site showed higher levels of DOC and total dissolved nitrogen(TDN).(2)The content of total phospholipid fatty acid(PLFA)was higher in paddy field and abandoned soil under different land use patterns.Bacteria were the dominant microbial groups in red soil,accounting for 69.24%-76.83%of the total PLFA,and were the main drivers of soil nutrient cycling.Among the bacterial groups,Gram-positive bacteria(G~+)and Gram-negative bacteria(G~-)accounted for a higher proportion of 19.45%-26.17%and 24.5%-35.78%,respectively.Fungi/bacteria(F/B)and Gram-positive bacteria/Gram-negative bacteria(G~+/G~-)were generally higher in forest soil.Compared with abandoned land,soil hydrolase activity,microbial biomass and microbial entropy were higher in paddy field,but lower in woodland.(3)Land use changes the composition and structure of microbial community by affecting soil p H and nitrogen nutrients.TN,p H,TDN and DOC are the main environmental factors affecting microbial community structure,accounting for 23.60%,8.70%,8.20%and 6.40%of the total interpretation degree,respectively.The total interpretation rate of soil physical and chemical properties and biological fertility indexes to microbial entropy reached 67.22%.The p H,texture,DOC and microbial characteristics were the main factors causing the change of soil microbial entropy.The contribution rates of DOC and PLFA,GMEA,Pielou evenness index and p H and Clay were 19.88%,19.39%,16.19%,13.01%,12.41%and10.13%,respectively.In conclusion,different land use types lead to different contents and availability of nutrients in soil,which leads to different community structure and extracellular enzyme activities of soil microorganisms under different land use patterns,and ultimately affects the size of soil microbial entropy.In the test of soil,most of the paddy field and abandoned land increased the eutrophic bacteria number Reduces the number of oligotrophic bacteria,increase the content of soil nutrient,and improve the effectiveness of soil nutrient and hydrolysis enzyme activity,thus soil microbial metabolism entropy has been reduced to a certain extent,promote the turnover of soil organic carbon.