Influence Mechanism Of Different Degradation Types And Their Regulation On Soil Microorganism

Globally,33%of the soil has been degraded due to excessive or improper use of human beings.Degradation leads to the continuous reduction of available cultivated land,grassland and forest land,which affects the food security and living health of human beings,reduces the biodiversity and the stability of the ecosystem,and causes incalculable damage to the ecological environment.In view of the current situation and characteristics of soil degradation in China and the limitations of the study,the soil samples from the northwest open-pit mining area,the south acid soil and the north sewage irrigation area were selected for the study.Under certain remediation measures,the effects of soil degradation and its regulation on soil and microorganism were discussed,and the similarity and difference of soil microbial community structure in different degraded environments were clarified The purpose of this study is to explore the microbial indicators of soil degradation and analyze their geographical distribution pattern,in order to provide theoretical reference for the restoration of degraded soil.The results are as follows:?1?After more than 20 years of vegetation restoration,soil pH of the reclaimed land decreased obviously in the northwest semi-arid ecological vulnerable area,soil organic matter?SOM?and total nitrogen?TN?accumulation of Robinia pseudoacacia×Pinus tabulaeformis hybrid forest were significantly higher than that of other plots.The content of TN and total potassium?TK?in the study area is extremely deficient,which will limit the maintenance of soil productivity.After reclamation,the proportion of Proteobacteria decreased significantly,while Acidobacteria increased significantly.The composition and structure of the dominant species of bacteria in the sample plots of Robinia×Pinus tabulaeformis and Robinia×Ailanthus×Ulmus were similar to the original appearance,and the richness and diversity of the communities were improved most significantly.?2?The pH of acid soil in south China increased with the increase of CaCO₃application.The contents of DOC and DON were increased by low and medium doses of calcium carbonate(2.25 and 4.5 t·hm^-2),but decreased by high doses of calcium carbonate(7.5 t·hm^-2).The application of CaCO₃ can change the process of soil nitrogen cycle and affect the mutual transformation of soil nitrogen.The application of medium dose CaCO₃ promoted soil respiration.The main composition of bacteria in all kinds of fields is similar,and the differences are mainly reflected in the relative abundance.The relative abundances of Acidobacteria,Chloroflexi,Gemmatimonades,Planctomycetes and Verrucomibia were increased,while those of Actinobacteria were decreased?p<0.05?.In addition,the application of low-dose and medium-dose CaCO₃increased the diversity of soil bacteria.?3?Soil pH,organic matter?SOM?,total nitrogen?TN?,available phosphorus?AP?and available potassium?AK?increased significantly with the application of biochar in northern sewage irrigation area,but the content of available Cd decreased accordingly.Crop planting had no significant effect on soil properties.Soil catalase and urease increased in different degrees,soil phosphatase decreased significantly,sucrase did not change significantly.The dominant classes of bacterial communities in the various fields with biochar were Proteobacteria,acidobacteria and Actinobacteria,and their relative abundances were different among different fields,and the relative abundance of these communities is different in different sites.The application of biochar can significantly improve the diversity and richness of soil microbial communities.?4?There are some similarities and differences in the bacterial community structure and driving factors of degraded soil ecosystem under different climatic and geographical environments in China.Proteobacteria is the most abundant of the three degradation types.The relative abundances of Acidobacteria,Planctomycetes and Gemmatimonades were higher than those of the controlled plots,while Firmicutes and Actinobacteria were lower.The community composition of bacteria in heavy metal contaminated soil in northern sewage irrigation area was higher than that in southern acid soil and northwest semi-arid vulnerable area,and the proportion of community composition in southern acid soil was relatively similar to that in northern sewage irrigation area.Among the three plots,the difference of?diversity index is obvious,and the richness and diversity level of heavy metal contaminated soil in the north sewage irrigation area is the highest,followed by the acid soil in the south,and the lowest in the semi-arid vulnerable area in the northwest.