Methane And Carbon Dioxide Emissions Exchange Characteristic Of Sphagnum Wetlands In Southwestern Hubei Province

As an important"window"for the exchange of methane and carbon dioxide,the carbon budget of Sphagnum wetland will affect the carbon balance of regional and global ecosystems.However,the carbon budget of different cover types of Sphagnum wetlands in subtropical and subalpine regions is still uncertain.In this study,the typical subtropical Subalpine Sphagnum wetland in Southwest Hubei Province was selected as the research object,and the methane,carbon dioxide emission fluxes,temperature,water level and other environmental factors of Sphagnum wetland with different cover types were continuously monitored by static box method.The purpose of this study is to explore the exchange characteristics of carbon flux in subtropical Subalpine Sphagnum wetland and the effects of cover types and main environmental factors on it,so as to enrich the understanding of carbon exchange in Sphagnum wetland.The main results are as follows:(1)The sphagnum moss wetlands in the study area mainly include bare land(B),sphagnum cover(S),and polytrichum cover(P),all of which are methane emission sources.The overall pattern is P>S>B,and the seasons are consistent.The characteristics of change,the methane emissions under each cover type are characterized by summer>autumn>spring>winter.There is no significant difference in methane emissions from different covering types of Sphagnum wetlands under light and dark conditions.(2)Among the carbon dioxide fluxes of Sphagnum wetland,the average value of net ecosystem carbon exchange and ecosystem respiration in the bare sample plot is 2.84 mg C·m^–2·h^–1.The average values of net ecosystem exchange,ecosystem respiration,and gross primary productivity of the Sphagnum sample plot respectively were-6.09,25.66,and-31.75 mg C·m^–2·h^–1.The average values of net ecosystem exchange,ecosystem respiration,and gross primary productivity of the polytrichum sample plot respectively were-6.09,25.66,and-31.75 mg C·m^–2·h^–1.The monthly and seasonal carbon dioxide fluxes of different covering types of Sphagnum wetlands are quite different.Ecosystem respiration and gross primary productivity are overall related to time changes,but there are differences between vegetation types.(3)Bare sample plot is a net carbon source,with an annual net carbon flux of32.43 mg C·m^–2·h^–1.Sphagnum and polytrichum sample plot are net carbon sink,with annual net carbon fluxes of respectively were 45.50 and 37.18 mg C·m^–2·h^–1.The carbon absorption of Sphagnum wetland with different cover types:Sphagnum sample plot>polytrichum sample plot>bare sample plot.(4)Covering type and temperature are the main factors affecting the carbon flux of Sphagnum wetland.Among them,the emission rates of methane and carbon dioxide from the three types of Sphagnum wetlands increased with the increase of temperature,and the relationship between the two was an exponential function.The water level has no effect on the methane flux of Sphagnum wetland,but has an effect on the carbon dioxide flux.