Characteristics And Microbial Mechanism Of Methane Emission From Grassland In Permafrost Regions Of Qilian Mountains

The Qinghai-Tibet Plateau is home to the largest permafrost in my country with abundant organic carbon(SOC)reserves.At the same time,the region is very sensitive to climate change.Global warming may cause the decomposition of organic carbon in the permafrost,thereby increasing the amount of greenhouse gases in the atmosphere.The current research on greenhouse gas emissions is mostly focused on carbon dioxide(CO₂)emissions,and there are relatively few studies on methane(CH₄)emissions.The flux of methane emissions in permafrost regions is related to the physical and chemical properties of the soil,the structure of microbial communities,and the abundance of functional genes.The relationship between degrees is unclear.In this study,the Yeniugou area of the Qilian Mountains in the northern Qinghai-Tibet Plateau was selected as the study area.From June 2019 to January 2020,the CH₄emission flux of different grassland types in the study area was measured by static chamber-gas chromatography,and the soil physics and chemistry were analyzed.Properties such as total carbon(TC),total nitrogen(TN),organic carbon(SOC),p H,water content.At the same time,real-time fluorescence quantitative(q PCR)technology was used to determine soil methanogens(mcr A)of different grassland types in Qilian Mountains.The functional gene expression of pmo A and methanotrophs(pmo A),while using Illumina Mi Seq sequencing technology to carry out high-throughput sequencing of methanogens and methanotropes,and study their composition at the target level,and obtain methanogens and methanogens at the same time.The community structure of methanotrophic bacteria.This study aims to clarify the CH₄ release characteristics of different grassland types and the microbial community composition that affects soil methane flux,and to understand the impact of soil physical and chemical properties on methane flux,which will help reveal the influence of CH₄ flux in permafrost regions of the Qinghai-Tibet Plateau Mechanism of microbiology.The main conclusions of this research are as follows:(1)The results of CH₄flux of different grassland types showed:1)The order of CH₄ flux was:alpine wet meadow>alpine meadow>alpine grassland,in which alpine meadow and alpine grassland showed absorption of atmospheric CH₄,alpine wet meadow was manifested as the release of CH₄ into the atmosphere;2)The seasonal variation of CH₄ flux was obvious,and the growing season(June,July,August,and September)was the period when CH₄ flux was relatively high;3)The diurnal variation of CH₄ flux presented a single-peak curve.From 08:00to 14:00,the flux of methane continues to increase,gradually decreased after 14:00,and basically remained at a negative value after 20:00.(2)The p H value of the soil in the alpine wet meadow was significantly lower than that of the alpine wet meadow and the alpine grassland.The water content,carbon and nitrogen content of the alpine wet meadow and the alpine meadow were higher than that of the alpine grassland.The soil TC and TN had obvious differences in different soil layers in the alpine wet meadow area.C/N and conductivity were not significantly different in different regions.The moisture content of the study area was significantly positively correlated with the carbon and nitrogen components in the soil.The higher the soil moisture content,the more obvious the accumulation of soil carbon and nitrogen.SOC and TC,TN showed a very significant positive correlation.TC and SOC showed a very significant positive correlation.The correlation between p H,conductivity,C/N and other soil physical and chemical indexes was not significant.(3)The copy numbers of the mcr A functional gene of the methanogens from 0?30 cm soil depth was from large to small:alpine wet meadow>alpine grassland>alpine meadow.The copy number of pmo A functional gene of methanooxidizing bacteria in 0-15 cm soil was from large to small:alpine meadow>alpine grassland>alpine wet meadow,which was the opposite of the order of the copy number of mcr A functional gene.The copy numbers of pmo A functional genes of the methanooxidizing bacteria in 15-30cm soil range from large to small:alpine grassland>alpine meadow>alpine wet meadow.(4)At the order level,the main methanogens in the alpine wet meadow were Methanomicrobiales,Methanosarcinales,Methanomassiliicoccales,and Methanomicrobiales.(Methanocellales),Methanobacteriales.Among them,the Methanomicrobial was the main dominant flora of each grassland type,and its abundance varies from 20.0 to 30.1%.The methanotrophic bacteria were mainly Methylococcales.Among them,Methylococcus occupied an absolute advantage in the methanotrophic flora,and its abundance varies from 85.9 to 96.6%.(5)The abundance of methanotrophic bacteria in different grassland types ranges from large to small:alpine wet meadow>alpine grassland>alpine wet meadow.The diversity and abundance of methanogens and methanotrophs in the 0?15 cm layer of alpine wet meadow were higher than those in the 15?30 cm soil layer,and the methanogens and methanobacteria in the 0?15 cm layer of alpine grassland and alpine meadow.The diversity and abundance of methanotrophic bacteria were lower than 15?30 cm soil layer.(6)CH₄ flux had a very significant positive correlation with soil temperature.There was a positive correlation between the carbon and nitrogen content in the soil and CH₄ flux.The methane flux was positively correlated with the soil moisture content and total carbon in the 0-15 cm layer of the alpine wet meadow.In this study,the moisture content of alpine meadow and alpine grassland had nothing to do with CH₄ flux.It showed that CH₄ flux in this study area was mainly affected by temperature and moisture.(7)The abundance of mcr A gene was positively correlated with CH₄ flux,and the abundance of pmo A gene had no obvious relationship with CH₄ flux.It showed that CH₄flux in the study area was mainly affected by the abundance of methanogens.The abundance of mcr A functional genes was significantly positively correlated with soil moisture content.(8)The diversity and richness of microbial communities were positively correlated with TC and SOC in soil.It showed that the carbon content in the soil in this study area determines the microbial community structure.The above results indicate that temperature and moisture were the most important factors affecting methane flux in permafrost regions.On the one hand,temperature and moisture determined the growth state of vegetation,thereby affecting the soil carbon content,on the other hand,affected the richness and diversity of microbial functional genes,that is,determined microbial activity.Ultimately,the higher soil carbon content provides sufficient conditions for the release of methane,and microbial activity directly determined the rate of methane production.