The Response Of Plant And Microbial Diversities Under Different Nitrogen Deposition And Effects On Greenhouse Gas Emission In Sanjiang Plain

Atmospheric nitrogen deposition,as an important phenomenon of global climate change,has an important impact on wetland ecosystem.This study aims to find the effects of nitrogen deposition on plant communities and soil microbial communities on greenhouse gas emission fluxes in wetland ecosystem,and provide theoretical basis for comprehensive analysis and assessment of the impact of global climate change on wetland ecosystem.This study is selected a long-term simulated nitrogen deposition platform in the Sanjiang Plain,the Institute of Nature and Ecology,Heilongjiang Academy of Sciences.The test set three levels of nitrogen addition:low nitrogen treatment(4gN.m^-2.a^-1),high Nitrogen treatment(8gN.m^-2.a^-1)and blank control(0gN.m^-2.a^-1),using high-throughput sequencing technology and static box-gas chromatography,to study the effects of Calamagrostis angustifolia wetland in Sanjiang Plain under nitrogen deposition on plant diversity,primary productivity,soil bacterial diversity,soil fungal diversity,and greenhouse gas emissions.The main results are as follows:?1?High nitrogen treatment significantly increased the Shannon-Wiener index of Calamagrostis angustifolia wetland;high nitrogen significantly increased the evenness index of Calamagrostis angustifolia wetland.High nitrogen treatment changed the seasonal dynamics of plant diversity in Calamagrostis angustifolia wetland.Both low nitrogen and high nitrogen treatments significantly increased the aboveground biomass in Calamagrostis angustifolia wetland,indicating that nitrogen is the main driving factor for primary productivity of Calamagrostis angustifolia wetland.?2?The addition of nitrogen increased the ammonium nitrogen and nitrate nitrogen contents and the differences between treatments were significant.The ammonium nitrogen content was significantly higher than that of nitrate nitrogen between treatments.Therefore,the soil inorganic nitrogen was mainly dominated by ammonium nitrogen in Calamagrostis angustifolia wetland.?3?Under different nitrogen deposition treatments,the soil bacteria Chao1 and Shannon index showed a single-peak seasonal change.With the seasonal change,the trend increased first and then decreased,reaching the maximum in summer.Nitrogen application did not change the seasonal change characteristics of bacterial diversity.The dominant species in the soil bacterial community in different seasons were Acidobacteria,Proteobacteria,and Chloroflexi.The relative abundances of dominant species changed significantly between different nitrogen treatments.Changes in soil ammonium nitrogen,nitrate nitrogen,and soil pH affect the composition and diversity of soil bacterial communities.?4?Under different nitrogen deposition treatments,the soil fungal Chao1 index showed a single-peak seasonal change.With the seasonal change,it increased first and then decreased,reaching the maximum in summer.High nitrogen changed the seasonal change characteristics of the soil fungal Chao1 index;Shannon index in different seasons The change was stable,and nitrogen application did not change the seasonal variation characteristics of Shannon index.The dominant species in the soil fungal community in different seasons are Ascomycota,Basidiomycota,and Mortierellomycota.Among them,Ascomycota is an absolute dominant group,and the relative abundance of different nitrogen treatments changes significantly.The main factors affecting the composition and diversity of soil fungal communities are soil nitrate nitrogen,ammonium nitrogen and soil total nitrogen.?5?Both low nitrogen and high nitrogen inputs significantly increased greenhouse gas emissions.Low nitrogen and high nitrogen treatments increased CO₂ emissions by47.5%and 47.9%,CH₄ emissions by 76.8%and 110.1%,and N₂O emissions by Volume increased by 42.4%and 10.6%.There was a significant exponential correlation between CO₂ emission flux and soil temperature,but no significant correlation with soil moisture content.There was a significant linear correlation between CH₄ emission flux and soil moisture content,but no significant correlation with soil temperature.The factors that affect N₂O emissions are more complex and have no significant correlation with soil temperature and soil water content.?6?Comprehensively analyze the relationship between plant-microbe-greenhouse gas emissions by constructing a linear regression model,and explain the dynamic response characteristics of greenhouse gas emissions to nitrogen deposition from the perspective of biodiversity.There was a significant linear correlation between CO₂emissions and plant,bacterial and fungal diversity.CH₄ emissions had a significant linear correlation with bacterial diversity,but not with plant diversity and fungal diversity.N₂O emissions showed a significant linear correlation with bacterial diversity,but not with plant diversity and fungal diversity.Bacterial diversity is the main influencing factor of greenhouse gas emissions under nitrogen addition.Nitrogen addition significantly increased the global warming potential of CO₂,CH₄,and N₂O in the Calamagrostis angustifolia wetland.