Effects Of Warming And Spartina Alterniflora Invasion On Functional Microorganisms And HONO And NO Gas Emissions In Wetland Soils

Wetland ecosystem is not only a sensitive and vulnerable area of global climate change,but also a hot area of alien plant invasion and expansion.As a key component of wetland ecosystem,soil microorganisms can participate in multiple soil ecological processes and play an important role in maintaining the health of wetland ecosystem.Excessive reactive nitrogen in the environment will affect the ecosystem and biodiversity,change the balance of greenhouse gases and threaten the quality of air,soil and water.Reactive nitrogen gases such as gaseous nitrite(HONO)and nitric oxide(NO)can directly affect the oxidation capacity of the atmosphere,the formation of haze and human health by producing hydroxyl(OH·).At present,the research on soil HONO and NO gas emissions mainly focuses on grassland,farmland and forest ecosystems,and the research on the gas emission flux and influencing factors of wetland ecosystem is relatively few.The research on wetland soil microorganisms mainly focuses on the activities of microorganisms in different types of wetland soils and their simple relationship with different environmental factors,However,there is insufficient research on the functional mechanism of soil microorganisms and the response mechanism under environmental change.To sum up,taking Chongming Dongtan wetland in Shanghai as the research area,this paper selects typical invasive species Spartina alterniflora and local species Phragmites australis to simulate the invasion in different planting proportions,simulates the warming of them through open top chambers(OTCs),and uses the dynamic box system to measure the gas emission fluxes of HONO and NO in the soil of Chongming Dongtan wetland under the warming and Spartina alterniflora invasion,high throughput sequencing and Geo Chip were used to analyze the changes and response characteristics of soil microbial community and functional genes,and to clarify the driving factors of soil HONO and NO under warming and Spartina alterniflora invasion.The main results are as follows:(1)The dominant archaea and fungi in Chongming Dongtan wetland soil are thaumarchaeota(57.40%?90.27%)and ascomycota(44.66%?61.67%).Warming significantly reduced the richness of soil archaeal and fungal communities,and significantly changed their species composition structure.The impact of Spartina alterniflora invasion was not significant,and the interaction of warming and Spartina alterniflora invasion only had a significant impact on the species composition structure of fungi.(2)There are a large number of functional genes related to carbon cycle in Chongming Dongtan wetland soil,and the microbial community is mainly bacterial community.It is found that proteobacteria has extensive metabolism,while planctomycetes and euryarchaeota have specific metabolism,which mainly carry functional genes related to anammox and methanogenesis.Warming significantly reduced the signal intensity of most functional genes in carbon,nitrogen,phosphorus and sulfur cycle,while Spartina alterniflora invasion significantly affected Thiosulfate oxidation gene sox V.The interaction of warming and Spartina alterniflora invasion had no significant effect on the functional genes of carbon,nitrogen,phosphorus and sulfur cycle.In the functional genes of carbon,nitrogen,phosphorus and sulfur cycle in Spartina alterniflora soil,except denitrification gene nor B and carbon fixation gene acl B,the signal intensity of other genes is higher than that in Phragmites australis soil,and warming significantly reduces the signal intensity of most functional genes in Phragmites australis soil,while Spartina alterniflora soil has less significant response to warming than Phragmites australis,and its related metabolic capacity is more stable.(3)The maximum emission fluxes of HONO and NO in Chongming Dongtan wetland soil were 1.50?68.44 ng N m^-2 s^-1 and 2.26?40.96 ng N m^-2 s^-1,respectively.The total emission in one dry wet alternation was 0.02?0.89 mg N m^-2 and 0.03?0.80mg N m^-2,respectively.Warming has a significant effect on soil HONO and NO emission fluxes,which can be increased by?10 times.Invasion significantly affects the maximum soil NO emission flux,but has no significant effect on HONO emission flux,and there is no significant difference under the interaction of the two.The emission fluxes of HONO and NO in Phragmites australis soil were higher than those in Spartina alterniflora soil,and warming exacerbated the emission difference between them.In a dry wet alternation,the emission fluxes of HONO and NO in Chongming Dongtan wetland soil will first increase and then decrease with the change of soil water content,and reach the emission peak at 0?10%and 0?20%WHC.(4)The emission fluxes of HONO and NO in Chongming Dongtan wetland soil were significantly correlated with most key functional genes of carbon,nitrogen,phosphorus and sulfur cycle,including CODH?Rga E?phenol?oxidase?amo A?nar B and cys J genes abundance can show a high negative correlation with both emission fluxes at the same time,and soil p H value shows a significant positive correlation with emission fluxes.Soil environmental factors and microbial key functional genes can explain more than 75%and 80%of HONO and NO emissions;Soil p H value,NO₃^-content and AOA abundance can directly affect soil HONO emission.Warming can affect HONO gas emission by changing soil p H and AOA abundance;Soil NO emission flux is mainly controlled by AOA,nir K and nir S gene abundance,and soil environmental factors can affect NO emission by affecting soil HONO emission,and there is an extremely significant and direct positive correlation between soil NO emission flux and HONO emission flux.