Response And Significance Of Greenhouse Gas Exchange To Simulated Warming In Yancheng Coastal Wetland

The coastal wetland ecosystem is in an important ecotone of land-sea interaction.The high primary productivity and special anaerobic environment make it an important carbon sink while also producing large amounts of carbon dioxide?CO₂?and methane?CH₄?.In the context of global warming,how does the exchange of greenhouse gases in coastal wetlands change?Can its carbon sink function be maintained?The uncertainty of these issues limits our understanding of the carbon cycle in this region.In this paper,two typical wetlands of coastal Phragmites australis and Spartina alterniflora in Yancheng were used as research objects,and the effects of warming on greenhouse gas exchange in the ecosystem were studied using open-top chamber?OTC?and static box observation.Focused on the responsive characteristics of ecosystem respiration(R_eco),net ecosystem CO₂ exchange?NEE?and CH₄ flux to short-term simulated warming,clarified the main factors that control the exchange of greenhouse gases in the ecosystem,and provides novelty experimental data for the regional carbon balance budget of coastal wetlands and the assessment of the potential effects of global warming.The main conclusions are as follows:?1?The greenhouse gas exchange in Yancheng coastal Phragmites australis wetland and Spartina alterniflora wetland has the characteristics of seasonal change.Throughout the growing season,the ecosystem is CO₂ carbon sink and CH₄ carbon source.The fluxes of R_eco,NEE and CH₄ were lower in the early and late growing season.R_eco peaked in July.NEE presents a negative value during the growing season of plants,and the ecosystem mainly displays CO₂ absorption.CH₄ flux peaked in September.Plant biomass has a greater impact on NEE and R_eco in the early growth season?May?.?2?The surface soil conductivity of Spartina alterniflora habitat has a significant effect on CO₂ flux?p<0.01?.The R_eco of Spartina alterniflora habitat is larger than that of Phragmites australis habitat,while the CH₄ flux is opposite.This study implies that plant invasions may cause an increase in ecosystem respiration flux and increase the carbon loss of the ecosystem.However,from the perspective of the greenhouse effect,plant invasion will not increase the overall warming potential.?3?There is a significant seasonal difference in the effect of warming on the carbon exchange flux of the ecosystem:warming at the initial stage of plant growth increases the biomass of wetland plants,but warming at high temperatures will inhibit plant growth;in the early growing season?April And May?,warming increases R_eco,and in the middle and late growing season?July and September?,warming decreases R_eco;in the middle and late growing season of Phragmites australis habitats?July and September?,warming leads to an average NEE net absorption flux decreased by 51.9%.In Spartina alterniflora habitat in the early and middle of the 2018 growing season?May and July?,the average net absorbed flux of NEE decreased by 34.1%,which suggests that the invaded ecosystem may have better resistance to stress;CH₄ flux was less affected by warming.