Temporal And Spatial Characteristics Of Carbon Emissions From Peat Swamps And Their Future Projections Under Changing Environments

Peatland is an important type of terrestrial ecosystem.At the same time,it is also the ecosystem with the fastest carbon accumulation rate and the largest carbon accumulation per unit area.Under the condition of climate change,the carbon stored in peat land will be released in the form of greenhouse gas.In this paper,Canada,which is rich in peatlands,is selected as the study area.The temporal and spatial variation laws of CO₂ and CH₄ in the study area are discussed by using the greenhouse gas concentration data retrieved by GOSAT satellite.At the same time,with the help of ERA5 reanalysis data,the change of greenhouse gas concentration in the study area under different temperature and precipitation conditions is analyzed,and the key factors of controlling greenhouse gas emission under changing environment are discussed.Finally,using CMIP6 climate model data,the greenhouse gas concentration under different socio-economic scenarios in the future is estimated by random forest algorithm.The main conclusions are as follows:Firstly,the change of greenhouse gas concentration in peatlands in Canada has strong interannual characteristics.Generally speaking,the greenhouse gas concentration in the study area gradually increases with the passage of years,with the most obvious increase in 2014 and 2015,while the growth in 2010 and 2012 is relatively slow.On the other hand,due to the influence of meteorological factors such as temperature and precipitation,the temporal and spatial characteristics of seasonal variation of greenhouse gas concentration in peatlands in Canada are also different.In terms of time distribution,he CO₂ concentration in peatlands in Canada in winter and spring is greater than that in summer and autumn,while the CH₄ concentration in spring,autumn and winter is greater than that in summer;In terms of spatial distribution,greenhouse gases in Canada are mainly concentrated in the peatland area of 50°N-60°N and 70°W-80°W,and diverge and decrease towards the polar and equatorial directions.In addition,the vertical distribution characteristics of CO₂ and CH₄ concentrations in peatlands in Canada show that the concentrations of CO₂ and CH₄ in each layer gradually increase with the passage of years;Decreases as height increases.Affected by topography and altitude,the changes of CO₂ and CH₄ concentrations are different.Secondly,the temperature and precipitation at 2m height are selected to analyze the changes of CO₂ and CH₄ concentrations in peatlands in Canada retrieved by GOSAT satellite.It can be seen that there is an obvious negative correlation between temperature and precipitation at 2m height and CO₂ concentration.In terms of temperature,the temperature will directly affect the vegetation growth and coverage in the study area,which have an important impact on CO₂.In terms of precipitation,the change of precipitation not only changes the water level of peatland in the study area,but also affects the concentration of greenhouse gases through the coefficient of scouring.On the other hand,the response of temperature and precipitation to CH₄ at 2m height lags behind.In terms of temperature,this is mainly because the enzymes that play a leading role in the production of CH₄ and the response of methanogens to temperature take a certain time to accumulate.In terms of precipitation,only when the precipitation accumulates to a certain amount will the anaerobic environment necessary for CH₄ emission be produced.Finally,a random forest model is constructed for the temperature,precipitation and GOSAT satellite greenhouse gas concentration at 2m in the historical period of CMIP6.By inputting the temperature and precipitation information at 2m in different socio-economic scenarios(SSP1-2.6,SSP3-7.0,SSP5-8.5),the machine learning algorithm is used to predict the future greenhouse gas concentration.The results show that for the time change,the CO₂ concentration and CH₄ concentration in the study area show an upward trend under the three socio-economic scenarios,The rising range is different among different scenarios;In terms of spatial change,the spatial distribution of greenhouse gas concentration in the three socioeconomic scenarios is relatively similar,and the difference of CO₂ concentration and CH₄ concentration in the East and west of the study area is obvious.At the same time,the high value of greenhouse gas concentration is mainly concentrated in the peatland area of 55°N-60°N and 90°W-100°W.