Characteristics And Mechanism Of Microorganism And Enzyme Activity Response To Soil Erosion

Soil erosion is one of the global environment problems which severely restrict human survival and development.It could cause serious soil and nutrients losses,land productivity decline,and severely damage land resources.In addition,erosion induced soil microbial community structure and enzyme activity changes will has a great effect on the storage of soil organic carbon?SOC?and soil carbon cycle,and then change global climate.At present,it is unclear about the mechanism of microorganism and enzyme response to soil erosion,and we can't accurately assess the dynamic change of soil biological characteristics after erosion.In this study,we have analyzed the dynamic change of soil biological characteristics in erosional and depositional sites of hilly red soil region of southern China,and quantified the relationships between soil basic physicochemical parameters and biological properties,to investigate the influence of soil erosion and deposition process on soil biological characteristics.The main research results are as follows:?1?Soil deposition is beneficial to increase soil carbon,nitrogen contents and enzyme activities.Results show that SOC,total nitrogen?TN?,dissolved organic carbon?DOC?,urease,acid phosphatase and catalase activity in most depositional soils are greater than those in erosional soils,soil deposition significantly improve soil fertility levels and enzyme activities.Furthermore,significant differences in nutrition levels and enzyme activities between erosion and deposition site 0³0 cm top soils are observed and differences gradually decrease with soil depth increasing.The variation rate range of SOC between erosional and depositional sites is 3.84%³6.42%,and TN is 54.64%⁷5.00%.SOC,TN,DOC contents and enzyme activities in erosional and depositional soils present an overall downward trend with soil depth increasing.?2?Soil erosion process significantly reduced the microbial abundance in erosional sites,while had no significant influence on microbial community composition.The content of soil microbial biomass carbon?MBC?in depositional site reached up to 0.90 mg g^-1,and was 1.75times higher than that in erosional site.While there is no significant difference of Shannon index?H?between erosional and depositional sites.Relative to soil H index,soil erosion have a more remarkable influence on microbial abundance.In addition,soil deposition process effectively improved soil nutrient availability.The depositional site with the DOC content of0.334 mg g^-1 is significantly greater than erosional sites.?3?Evident linear correlations were observed among soil enzyme activities,soil carbon and nitrogen contents.Except for soil sucrase activity,Soil urease,acid phosphatase and catalase activities all have highly significant positive correlations with SOC,TN and DOC.The correlation coefficient from 0.68 to 0.95.Among all parameters,SOC showed a primary contribution to the variance of soil enzyme activity.SOC is the main control factor of affecting soil enzyme activity.Furthermore,erosion induced changes in soil physicochemical parameters have significant effects on soil microbial community composition.The results showed that the microbial community composition was substantially influenced by DOC,as DOC explained up to 19.3%of the variation in microbial community composition.In conclusion,soil deposition is beneficial to enhance soil microbial biomass and enzyme activities,while has no significant impact on improving microbial community diversity.Water erosion provided greater impact on level of soil microbial biomass than community composition.