Effect Of Permafrost Collapse Soil Microbial Community At The Genus Level Of Under Different Land Cover Types In The Qinghai-Tibet Plateau

Under the current background of global warming,permafrost has undergone widespread degradation,which will lead to the degradation of soil organic carbon previously preserved in permafrost regions and release into the atmosphere in the form of greenhouse gases.As an important part of the biogeochemical cycle of soil organic carbon,microorganisms play a key role in the decomposition of organic carbon.At present,a large number of studies have shown that there is a close relationship between the bacterial community structure and the cycle of soil organic carbon,but most of the existing research has focused on the research at the phylum level,which is far from enough to understand the relationship between microorganisms driving carbon decomposition.At the same time,the rapid warming of permafrost regions in recent years has led to rapid degradation of permafrost.One of the important phenomena is the occurrence of thaw slump landforms.However,changes in soil bacterial communities induced by thaw slump and their implications for changes in soil carbon and nitrogen are still unclear.In this paper,the meadows in the Qinghai-Tibet Plateau’s Fenghuo area and Qumalai area where thaw slump occurred as the research area,through the control area without slumping in the study area,the area in the process of slumping,and the subsidence area that has slumped.The soil under various micro-landforms was sampled,and the soil layers of 0-10 cm,10-20 cm,and 20-30 cm were collected according to the depth.The 16S r RNA V₃-V₄ region of the sample was sequenced using Illumina sequencing technology,and the diversity,composition,and distribution abundance of the microbial community were studied at the level of bacterial genus,and the physical and chemical properties of the soil（water content,bulk density,p H,electrical conductivity,organic carbon,inorganic carbon,total nitrogen content）and soil bacterial community structure and their relationships.The purpose of the study was to clarify the changes in the abundance of each bacterial genera and its relationship with soil physical and chemical properties.The main findings are as follows:（1）Thaw slump significantly changed the physical and chemical properties of the soil.The p H value was the largest in the subsidence area and the smallest in the control area;the organic carbon content was the largest in the control area and the smallest in the slump area;the total nitrogen was the largest in the control area and the slump area was the smallest.The area is the smallest;the soil moisture content is the highest in the control area and the smallest in the subsidence area at the surface 0-10 cm,but at 10-20 cm and 20-30 cm,the content is the highest in the slump area and the smallest in the control area.Through correlation analysis of soil physical and chemical properties,it was found that there was no significant correlation between depth and all physical and chemical factors.There was a significant positive correlation between inorganic carbon and total organic carbon,a significant positive correlation between total nitrogen and total organic carbon,and a significant negative correlation between total nitrogen and the ratio of organic carbon and total nitrogen.（2）By analyzing the abundance of bacterial genera,in the two study areas,a total of 11 dominant genera were found,namely Gaiella,RB41,Nitrospira,Nocardioides,Acidobacteria,Anaerolineaceae,Gemmatimonadaceae,Acidimicrobiales,Gaiellales,JG30-KF-CM45,Micrococcaceae.（3）In the abundance of bacterial genera,Micrococcus was negatively correlated with water,Anaerolineaceae was positively correlated with soil organic carbon,Nitrospira,RB41 and Gemmatimonadaceae were negatively correlated with TN,Anaerolineaceae and JG30-KF-CM45 were positively correlated with TN,RB41 was positively correlated with C:N ratio,and J30-KF-CM45 was negatively correlated with C:N ratio.Therefore,Microcococacaee,Ni-trospira,Gemmatimonadaceae,Anaerolineaceae,RB41 and J30-KF-CM45 can be used as indicator genera for changes in soil physicochemical factors in thermokarst soils.（4）In the area where thaw slump occurred,theα-diversity of the bacterial community was the largest in the control area and the smallest in the subsidence area;however,the richness of the bacterial community was the largest in the subsidence area and the smallest in the slump area.（5）Through a comprehensive analysis of the relationship between soil physical and chemical properties and microorganisms,it was found that the relationship between soil organic carbon content,total nitrogen and carbon-nitrogen ratio and bacterial community structure was the most significant.The rapid loss of soil organic carbon and total nitrogen is an important mechanism affecting the structure of bacterial communities.