| The contradiction between human and land was prominent in karst areas,and the phenomena of soil and water loss and rocky desertification are serious.Vegetation restoration was an effective key measure for ecological control of rocky desertification.After vegetation restoration,the rapid accumulation of organic matter in the whole soil after transfer from farmland had been extensively studied,but it was stilled unclear how the carbon pool and microbial community in the soil aggregates change.Understanding the interaction between aggregate soil organic carbon and soil microbial community was very important for studying the carbon cycle in soil after vegetation restoration.With the extensive application of nano-materials such as nano-silver,the contact opportunities between soil and nano-silver have greatly increased.However,most of the studies are in non-karst areas,and there were few studies on the impact of nano-silver on soil in karst areas.In this paper,the effects of three concentrations of nano-silver,low(10 mg·kg-1),medium(50 mg·kg-1)and high(100 mg·kg-1),on the physical and chemical properties and microorganisms of soil in karst areas were studied,and the evolution of soil physical and chemical properties,organic carbon chemical components and microbial community characteristics of different aggregates in the process of vegetation restoration was analyzed systematically and comprehensively,and the microbial community structure of the research object was clarified,The response of soil microbial community to different vegetation restoration stages and its driving factors,as well as the effect of nano-silver in karst soil were discussed.In this study,the high-throughput sequencing of 16S rRNA and ITS genes combined with 13CNMR spectral analysis were used to clarify the microbial communities and SOC compounds in five sample plots of soil（corn field,grassland,shrub,secondary forest and primary forest）;According to the best water screening method,the soil is divided into aggregates with different particle sizes（POM:particulate bound organic matter 53～2000μm;MAOM:mineral-bound organic matter<53μm）.The following conclusions were obtained from the result analysis:1.With the vegetation restoration,the contents of SOC,TN,DOC,E-Mg,E-Ca and SM generally increased（P<0.05）.Alkyl C,Carboxylic C and O-alkyl C in POM increased,while only Carboxylic C and O-alkyl C in MAOM increased significantly.However,Aromatic C decreases with vegetation restoration.Refractory carbon and degradable carbon in POM play an important role in the increase of SOC,while only degradable carbon in MAOM played an important role in the increase of SOC.The accumulation of soil particles forms POM.This process will protect the internal organic matter and reduce the contact between microorganisms and oxygen to decompose,and ascomycetes decompose plant-derived organic matter,making the content of SOC and POM positively correlated,indicating that POM played a vital role in the storage of SOC in the restoration of karst vegetation.2.There were differences in soil microbial diversity and community structure between POM and MAOM in different vegetation restoration stages in karst areas.Effects of POM and MAOM on soil microbial communities during vegetation restoration in karst areasα、βDiversity had a significant impact.Because MAOM’s tiny pores provide a stable habitat for microorganisms,MAOM’s microbial community contains richer and more diverse microbial communities（according to Chao 1 and Shannon index）.The dominant bacteria in the soil of POM and MAOM in the karst area were partially similar in each vegetation restoration stage.Thickcklyophila,Ascomycete and Acidobacter are the dominant bacteria with higher abundance in the soil of POM and MAOM in each vegetation restoration stage,indicating that these dominant groups were highly adaptable to severe environmental changes.However,Proteobacteria occupies a high relative abundance in POM,and Greenbay bacteria occupies a high relative abundance in MAOM.It shows that POM and MAOM also have certain differences in the dominant bacteria.3.The soil microbial communities of POM and MAOM in karst areas mainly participate in the carbon and nitrogen cycling process at each vegetation restoration stage,and the relative abundance of main functional groups changes with the vegetation restoration process.Aerobic-chemoheterotrophy,nitrification and other bacterial functional groups showed an increasing trend with the vegetation restoration process,which was consistent with the change trend of soil nitrogen content,indicating that the increase of these functional groups promoted the process of nitrogen fixation in karst soil.The difference in the relative abundance of the functional microbial communities involved in the carbon cycle process,such as Chemoheterotrophy,Saprotrophh and Saprotrophy-Symbiotroph,may be an important reason for the difference in the content of soil organic carbon.4.Nano-silver had no significant effect on the physical and chemical properties of soil;When the soil is treated with nano-silver,the effect on the abundance of microbial community was very small,and there was no significant difference on the diversity of bacterial community.After nano-silver enters the soil,the relative abundance of Thick-wall and Curvularia is increased,and the relative abundance of Actinomyceta and Proteobacteria is decreased.After the soil in karst area was treated with nano-silver,it had a significant impact on the microbial community and the functional flora of decomposing aromatic compounds. |
