Microbiological Mechanism Of Earthworm Affecting Greenhouse Gas Emission From Marsh Soil Under Warming

Wetland is an important fragile ecosystem in the world,and its biogeochemical cycle process is sensitive to climate change.greenhouse gas emissions are an important process of carbon and nitrog en cycles in wetland ecosystems and are significantly affected by temperature changes.Studies have confirmed that as a widely distributed"soil ecological engineer",earthworms,as a typical large soil animal,play a non-negligible role in shaping soil st ructure and regulating soil ecological processes and functions.Under the background of climate warming,the impact mechanism of earthworms on wetland soil greenhouse gas emissions,especially the microbial diversity and its functional response under the regulation of earthworms still needs further study.This thesis takes the soil of the marsh wetland in the Sanjiang Plain as the research object.Through simulation experiments,different ecological types of earthworms(the epiphytic type Eisenia foetida and Drawida Japonica Michelsen)under increasing temperature(1 4.2?,15.7?,and 17.2?)on the effect of soil greenhouse gas emissions and its microbial mechanism.Earthworms can significantly affect the emission rate and cumulative emission of greenhouse gas es such as CO₂,CH₄ and N₂O in soil,and the degree of influence varies with the ecological type and density of earthworms.The influence of inhabiting earthworms on greenhouse gas emissions is significantly higher than that of epitope earthworms.At elevated temperatures,inoculation of two ecotypes of earthworms(epibenthos and endobenthos)promoted soil CO ₂ and N₂O emissions,and strengthened the inhibition of earthworms on CH ₄ absorption.The greater the warming amplitude,the greater the inhibition o f CH₄ absorption.At elevated temperatures,inoculation of endobenthos promoted CH ₄ emission at the later stage of incubation.Warming,earthworm density,earthworm ecotype and their interactions significantly affected the physicochemic al properties of wetland soil.Earthworm inoculation significantly affected the carbon excitation effect of wetland soil,and the promotion effect of earthworms was significantly higher than that of earthworms.Under warming,earthworm inoculation significantly changed the community diversity and structure of methanogens and methanotrophs in wetland soils,thus affecting soil CO ₂ and CH₄ emissions.Different earthworm ecotypes have different effects on methanogen community and methanotroph community.At elevated temperatures,inoculation of epiphytic earthworms could improve the diversity of methanogens and reduce their community richness.Inoculation of earthworms reduced the diversity and richness of methanogen community.The inoculation of epibenthic earthworms or endobenthi c earthworms increased the community diversity of methanotrophs and re duced their community richness.Methanobacteriaceae is the dominant group of methanogenic bacteria in epitope earthworm soil inoculated at elevated temperature,and the effect of methane emission is mainly through CO ₂.Methylosinus and Methylocystis were both type II methanotrophs in the soil methanotrophs inoculated with endosymbionts.Under warming,the inoculation of epibenthic earthworms increased the richness and diversity of ammonia oxidizing bacteria community,while the inoculation of endobenthic earthworms decreased the richness of ammonia oxidizing archaea community and increased its diversity.At different culture stages,the microbial community structure of ammonia oxidizing archaea and ammonia oxidizing bacteria showed different correlation with environmental factors.At elevated temperatures,inoculation of Eisenia foetida increased the diversity of ammonia-oxidizing bacteria,nirS-type and nirK-type denitrifying bacteria communities,and reduced the abundance of two denitrifying bacteria.At elevated temperature,the diversity and richness of nirS-type denitrifying bacteria community were increased by inoculating earthworms.Inoculation of Eisenia foetida improved the diversi ty and richness of nirK-type denitrifying bacteria community,and the composition of nirK-type denitrifying bacteria community varied significantly with culture time.