Characteristics Of Greenhouse Gas Emission And Its Influencing Factors In The Headwater Wetland Of Wayan Mountain Under Simulated Precipitation

In the context of global climate change,the impact and feedback of extreme climate change on greenhouse gases has become a current research hotspot,and changes in precipitation have caused changes in the carbon and nitrogen cycle of the alpine wetland ecosystem on the Qinghai-Tibet Plateau.As a sensitive area of?climate change,the Qinghai-Tibet Plateau is experiencing the impact of climate change.As an important part of the alpine ecosystem,the alpine wetland is an ideal place to reveal the response of precipitation changes to the alpine wetland ecosystem.Studying the relationship between greenhouse gas release and precipitation changes in alpine river source wetland is conducive to in-depth understanding of the impact of alpine wetland ecosystems on climate change and its response to climate change,as well as reasonably predicting future trends and responding to the impact of climate change on carbon and nitrogen cycles.Promote national strategies for addressing climate change,and formulate adaptive management for ecological restoration of alpine wetlands to provide scientific reference.In order to explore the impact of precipitation changes on greenhouse gas emissions from alpine river headwater wetland ecosystems,the"static box-gas chromatography"method was used to explore the increase and decrease of precipitation in global changes.The alpine river source wetland ecosystem in Wayan Mountains was studied.The experiment set up a natural control group and four treatments through a precipitation simulation device:increase the precipitation by 25%(about 533.5 mm),reduce the precipitation by 25%(about320.1 mm),increase the precipitation by 75%(about 746.9 mm)and precipitation reduction75%(about 106.7 mm),the emissions of CO₂,CH₄and N₂O from the alpine river source wetland under different precipitation were measured,and the cumulative flux in the growing season and the global warming potential(GWP)were calculated accordingly,concluded as follow:(1)The range of CO₂flux under different precipitation treatments in the 2020 growing season is:115.9?249.7 mg·m^-2·h^-1,and the CO₂flux of each treatment is:+75%>+25%>-75%>CK>-25%mode;CO₂flux range in 2021:14.3?51.9 mg·m^-2·h^-1,CO₂flux performance of each treatment:+25%>CK>-75%>+75%>-25%mode.The CH₄flux in the 2020 growing season under different precipitation treatments ranged from-6.7 to 7.8?g·m^-2·h^-1,and the CH₄flux in each treatment was as follows:+75%>CK>+25%>-75%>-25%mode;the CH₄flux range in 2021 is:-5.5?0.6?g·m^-2·h^-1,and the CH₄flux of each treatment is:CK>+25%>+75%>-75%>-25%mode.The range of N₂O flux under different precipitation treatments in the 2020growing season was:-1.2?2.5?g·m^-2·h^-1,and the N₂O flux of each treatment was as follows:+75%>-75%>CK>-25%>+25%mode;the N₂O flux range in 2021is:-4.7?0.6?g·m^-2·h^-1,and the N₂O flux performance of each treatment is:CK>-75%>+25%>+75%>-25%mode.(2)Aboveground and belowground biomass has a significant impact on the fluxes of CO₂,CH₄and N₂O in alpine wetlands,and the relationship between the content of aboveground and belowground biomass under different precipitation changes in the2020 and 2021 growing seasons and the three greenhouse gases it was concluded that in the natural state and under all treatments,the CO₂flux was significantly positively correlated with the above-ground and below-ground biomass,and the total carbon in the 0?10 and 10?20 cm soils,but not with p H and electrical conductivity.The relationship between the biomass and aboveground and underground biomass was inconsistent,and the correlation with 0?10 cm soil total nitrogen and total carbon was not significant.Significant negative correlation,extremely significant negative correlation with 10?20 cm p H,significantly positive correlation with 0?10 cm p H under-75%treatment;?25%N₂O flux was significantly negatively correlated with aboveground and underground biomass,+75%treatment had a significant positive correlation,+25%treatment had a significant positive correlation with 0?10 cm soil total nitrogen,+75%treatment had a very significant negative correlation with 0?10cm soil total nitrogen,and 10-20 cm soil total nitrogen and total carbon There was a very significant positive correlation,and CK,?25%,+75%treatments were all significantly negatively correlated with p H.There were significant differences among environmental factors under different precipitation treatments.CO₂,CH₄and N₂O were influenced by aboveground and belowground biomass,soil total nitrogen and carbon,soil p H and electrical conductivity to different degrees.(3)Precipitation changes have different effects on the release of CO₂,CH₄and N₂O from alpine river headwater wetlands:precipitation changes in the 2020 and 2021growing seasons have a significant impact on CO₂emission fluxes,and?25%and?75%treatments in the growing season The cumulative CO₂fluxes were:25472.7,48687.8,17207.9,22142.7,22096.7 kg·hm^-2,with significant differences.The CO₂fluxes were significantly positively correlated with soil moisture in the CK group,25%and 75%treatments;The cumulative CH₄fluxes under each treatment were:-23.0,-24.1,-87.1,-27.7,-48.6 kg·hm^-2,with significant differences between increasing and decreasing rainfall.CH₄fluxes in the CK group,+25%,there was a significant negative correlation with soil moisture under the+75%treatment,and a significant positive correlation with soil temperature under the increased rainfall treatment.When the precipitation increased to a certain extent,the CH₄exchange flux showed an overall absorption state;N₂O cumulative flux under each treatment Respectively:286.6,-134.8,-301.7,-179.1,95.0 kg·hm^-2,there were significant differences among the treatments,and the N₂O flux was significantly positively correlated with soil moisture under the-25%treatment.Moisture is the main factor affecting CO₂flux,and CH₄flux is affected by soil temperature and moisture.(4)The 2020 growth seasons of the Wayanshan Riverhead Wetland under different precipitation treatments were CK:28760.9 kg CO₂-eq·hm^-2,+25%:57433.5 kg CO₂-eq·hm^-2,-25%:24337.5 kg CO₂-eq·hm^-2,+75%:26162.6kg CO₂-eq·hm^-2,-75%:26346.0 kg CO₂-eq·hm^-2.The contribution rate of CO₂flux in the growing season in2020 reaches 98.88?100.45%,the CH₄flux contribution rate is-0.06?-0.39%,and the N₂O flux contribution rate is-0.39?1.19%.The 2020 growing season is CK:22843.9kg CO₂-eq hm^-2,+25%:40259.9 kg CO₂-eq hm^-2,-25%:11015.0kg CO₂-eq hm^-2,+75%:19150.8 kg CO₂-eq·hm^-2,-75%:18377.5kg CO₂-eq·hm^-2.The contribution rate of CO₂flux in the growing season in 2020 will reach98.36?108.03%,and the contribution rate of CH₄flux will be-0.83?0.09%,the N₂O flux contribution rate is-7.2?1.55%.The comprehensive analysis shows that under the background of changes in precipitation,the CO₂flux doubled under the+25%treatment,thereby releasing more greenhouse gases,enhancing the atmospheric greenhouse effect,and producing a positive feedback on climate warming.This study provides an important scientific basis for clarifying the process of carbon and nitrogen cycling in the alpine river source wetlands of the Qinghai-Tibet Plateau and improving the Earth system model,which is of great significance for maintaining the ecological system security of the Qinghai-Tibet Plateau and responding to climate change.