Study On Greenhouse Gas Emission Flux Of Riverside Wetland In Grassland During Spring Thawing Period

Freezing-thawing alternation is an important natural phenomenon widely existing in the ecosystem of middle and high latitudes,which plays an important role in the carbon and nitrogen cycle of soil in cold regions.Under the background of global climate change,the phenomenon of freeze-thaw alternation is more extensive and common,and the influence and feedback of freeze-thaw pattern change on soil greenhouse gas emissions have become a hotspot in ecological research.Proven in the process of soil freezing and thawing alternation,especially spring soil melting process,the greenhouse gas emissions characteristics and the influence mechanism of action of flux,seasonal freezing and thawing soil in greenhouse gas emissions to the assessment of the greenhouse effect,clarify freeze-thaw alternation effect on soil nutrient cycle and the influence of soil enzyme activity,to predict the ecological impact of climate change,has important scientific significance.In Inner Mongolia,this article selects the typical savanes anti easy-restoration degree riverside with Phragmites australis and Carex appendiculata two typical wetland plant communities,the static camera obscura method is adopted in late March to the end of May,2018 greenhouse gas measuring and sampling the soil freezing and thawing period,the freezing phase of wetland soil in greenhouse gas emissions and freeze-thaw alternation of impact factors of different plant communities.The research results show that:?1?During the spring thawing period,the CO₂ emission fluxes of the two plant communities increased gradually with soil thawing.In addition,the CO₂ emission fluxes of the soil of the Carex appendiculata soil in the early thawing period were higher than those of the Phragmites australis soil,and the CO₂ emission fluxes of the soil of the Phragmites australis in the late thawing period were higher than those of Carex appendiculata.Phragmites australis is an important source of methane emission.The discharge flux of CH₄ in Phragmites australis increased gradually with soil thawing,while the total change of CH₄ discharge flux in the soil of Carex appendiculata was very small.In the spring thawing period of soil of the two plant communities,March and April are the"source"of soil N₂O,and May is the sink of soil N₂O.On the whole,the greenhouse gas emission and absorption of Phragmites australis soil were higher than those of Carex appendiculata?P<0.05?.?2?The differences in greenhouse gas emissions of different plant communities are mainly determined by the spatial heterogeneity of soil physical and chemical properties.Stepwise regression analysis showed that CO₂ and CH₄ of Phragmites australis community were mainly affected by soil microbial nitrogen and sucrase activity,and soil ammonia nitrogen was the dominant factor of Phragmites australis community N₂O.CO₂ in the Carex appendiculata community was mainly affected by soil temperature,and soil nitrate nitrogen was the dominant factor of N₂O in the Carex appendiculata community.?3?The comprehensive global warming potential on the centennial scale shows that the Phragmites australis community is significantly higher than the Carex appendiculata?P<0.05?,and the warming effect of different plant communities is different,and the Carex appendiculata community can effectively reduce the increase of atmospheric temperature.In general,differences in soil nutrients and microbial activities under different plant communities affect greenhouse gas emissions.Under the condition of global climate change,the change of soil freeze-thaw pattern will affect greenhouse gas emissions through affecting soil temperature,humidity,soil nutrient turnover,microbial activities,etc.,and the soil greenhouse gas emissions in spring thaw period cannot be ignored.In addition,when evaluating the greenhouse gas emissions of wetland soil,both the freeze-thaw process of soil and the differences between wetland plant communities should be taken into account.