Response Of Soil Microorganisms And Organic Functional Groups To Trace Elements

Soil erosion plays an important part in the global geochemical cycle of elements.It not only causes soil loss,but also spatially redistributes soil Nutrients.The research on the redistribution of nutrient elements mainly focuses on the major elements such as carbon,and a relatively systematic theoretical system has been formed.The migration and loss of trace elements that as a natural nutrient resource in terrestrial ecosystem due to erosion not only reduce the level of land productivity,but also pose a threat to downstream water and aquatic organisms,and affect the material circulation in local areas.Therefore,the redistribution of trace element should be brought to the forefront.This study collected soils from a typical agricultural land rich in zinc(zinc),manganese(Mn),copper(Cu).To determine the response characteristics of microbial communities and organic functional groups to trace elements,the changes of physical and chemical properties and crop yield of original soil were determined first under the condition of long-term application of trace elements.Adjacently,the microbial community composition and diversity in the soil treated with trace elements and control plots(CK)were analyzed by high-throughput sequencing.The aggregates fractionated into?250,250-125,125-63,63-20,and?20?m by settling tube were analyzed to determineand the element content of Zn,Mn and Cu,and the contents of organic functional groups.Research indicates:(1)Long-term use of Zn,Mn,and Cu elements did not change the species composition of the microbial community in the soil,but significantly increased the bacterial?diversity of topsoils.Bacteria in the soil of the response of trace element to a greater extent than fungi,this was mainly related to the differences in the adsorption efficiency and response mechanism of bacteria and fungi to trace elements.Mn element improved the adaptability of the bacterial community to the changes of external environmental factors,while Cu element increases the sensitivity of the fungal community to changes in environmental factors.The response of bacteria and fungi to trace elements are mainly based on the selective adsorption of trace elements.(2)The content of SOC in the treated plots was at a low level(6-12 g·kg^-1)and was not significantly improved after applying Zn,Mn,and Cu fertilizer.Nevertheless,the three trace elements were enriched to different degrees:Zn and Cu fertilizers significantly increased the total content of Zn and Cu(the degree of enrichment was above 30%and 80%respectively),but no evident Mn enrichment was observed under Mn fertilizer treatment(the degree of Mn was within 5%).The highest concentration of Zn,Cu,and Mn was observed in the?20?m fractions,especially Cu element.(3)Long-term application of trace elements significantly did not change the structure of soil organic carbon.C-O(polysaccharide)was unstable and content of this was largest,and the resistance of organic carbon was low.The functional groups(C-O,C=O and C=N)were positively associated with the accumulation of Cu in the soil,while the correlation between Zn and Mn elements and organic functional groups is limited by the content of organic functional groups and the adsorption efficiency of trace elements.This study identified the soil microbial responses to different trace elements and revealed the important role of organic functional groups in the distribution and accumulation of trace elements.Meanwhile,the rule of the distribution of trace elements in aggregates with different particle sizes is helpful to understand the process of trace elements redistribution under erosion conditions.