Research On Key Factors And Mechanism Of Natural Restoration Of Soil Microbial Community In Mining Area

Soil is the largest biological habitat.Understanding the characteristics and evolution process of soil biodiversity under different regions and management measures will help us explore the controlling factors of soil microbial population distribution and quantity,and provide theoretical basis and guidance for human ecological environment governance.In this study,Zhalainuoer mining area was taken as the research area,and the soil in the subsidence area and the soil in the unexploited area with different subsidence years were selected as the research objects.The related indexes of physical and chemical properties of plants and soil were investigated and determined,and the genetic information and related annotation information of bacteria and fungi at the door level were obtained,and the natural recovery laws of microbial communities,soil and vegetation were preliminarily explored.Finally,the main driving factors were found through correlation analysis,and the natural recovery mechanism of soil microbial communities in the subsidence process was explored from the perspectives of microbial flora function and evolution.The main conclusions are as follows:（1）After 15 years’natural recovery,although the macroscopic performance（vegetation coverage and diversity index,soil moisture content and p H）is similar to that of the subsidence area,their internal composition（vegetation biomass and evenness index,soil mechanical composition and related indexes of carbon,nitrogen,phosphorus and potassium）is different,indicating that the subsidence area has formed a new steady state after natural recovery,which is different from that before subsidence.（2）The natural restoration law of vegetation in grassland mining area is that the coverage and biomass are increasing year by year,and the coverage and biomass of vegetation are about 160%more than that of subsidence for 10 years.The diversity index and evenness index both increased at first and then decreased slowly.The life forms of dominant species changed from biennial herbs to perennial herbs,and from single life forms to multiple life forms.The natural recovery law of soil physical and chemical properties in grassland mining area is that subsidence gradually changes soil texture from clay to sand.With the increase of subsidence time,the related indexes of nitrogen and potassium changed obviously,that is,the total nitrogen first increased and then decreased,the nitrate nitrogen content first decreased and then increased,and the ammonium nitrogen content gradually decreased and then tended to be flat,basically stable at 35 mg/kg;The contents of total potassium and available potassium increased first and then decreased.The natural recovery law of soil microbial community in grassland mining area is that the chao index and shannon index of bacteria first increase and then decrease with the increase of subsidence time,and the variation law of bacterial abundance of dominant phenotypes（stress tolerance,aerobic and Gram-negative）is consistent with the diversity index;Fungal diversity index showed a trend of increasing first and then decreasing,and the abundance of pathotrophic fungi in dominant fungal trophic types was consistent with the change of fungal diversity index.（3）N-related indicators（TN,NO₃N and NH₄N）might be the key factors driving the natural recovery of bacterial communities,while K-related indicators（TK and AK）might be the key factors driving the natural recovery of fungal communities.（4）From the perspective of microbial evolution and flora function,combined with the correlation changes between vegetation and soil physical and chemical properties,the natural recovery mechanism of soil microorganisms can be considered from three aspects:（1）Plant dominance:the community composition of plant species and the community structure of bacteria and fungi change synergistically.Vegetation coverage and biomass increased year by year,while vegetation diversity and uniformity recovered,litter and root exudates provided nutrients and colonization space for specific microorganisms,and soil nutrients changed accordingly.（2）Soil dominance:The soil texture changed from clay to sandy soil,and the contents of SOM and TN related to soil clay particles also decreased year by year.Plants growing with different soil nutrient contents were different from their corresponding microbial communities.（3）Microbial dominance:harmful biota are abundant in the early stage of subsidence,which inhibits plant growth.The spatial distribution in soil and the mineralization rate of nutrients are closely related to nutrient content.The harmful biota coexisted with the beneficial biota in the late stage of subsidence,and the positive feedback was greater than the negative feedback.The biomass and coverage of vegetation increased year by year,and the content of soil nitrogen,phosphorus and potassium related indicators gradually recovered.There are 33 pictures and 5 tables in this thesis.