Analysis Of Greenhouse Gas Flux And Global Warming Potential In Different Permafrost Zones Of Daxing'an Mountains

Since the industrial revolution,greenhouse gas emissions have continued to increase,resulting in global warming,temperature rise of 1.1 ?,and frequent occurrence of extreme weather.Permafrost area accounts for 21.8% of the global land area,which is extremely sensitive to climate change.Global warming leads to the degradation of permafrost.The stored carbon and nitrogen in the form of CO₂,CH₄ and N₂O are released in large quantities,exacerbating global climate change.In this study,the permafrost region of Daxing'an mountains was selected to explore the feedback of greenhouse gas fluxes to climate warming in permafrost regions,mainly divided into two aspects:?1?research the characteristics of greenhouse gas fluxes in the continuous permafrost,discontinuous permafrost and island-shaped permafrost,combined with the characteristics of environmental factors,analyze the differences in the greenhouse gas fluxes in the three types of permafrost regions and the reasons for the differences;?2?research the changes of greenhouse gas fluxes in the continuous permafrost during the autumn freezing period,and analyze the impact of the increase in freeze-thaw cycle frequency and duration on the greenhouse gas fluxes during during global warming.In regions of continuous,discontinuous and island-shaped permafrost regions,the sensitivity of soil temperature and water content to climate change decreases in turn,the ecosystem of continuous permafrost is more fragile and more strongly affected by climate change;p H and TOC shows continuous permafrost <discontinuous permafrost <island-shaped permafrost,but NH₄⁺-N and NO₃^--N shows discontinuous permafrost <continuous permafrost < island-shaped permafros.The average of CO₂ fluxes in the three types of permafrost regions are?105.50±41.25?,?127.15±55.28?,?342.10±44.37?mg·m^-2·h^-1,and the average of CO₂ fluxes in the continuous and discontinuous permafrost are significantly less than the island-shaped permafrost regions?p<0.05?,soil temperature and TOC are the main influencing factors for the difference of CO₂ fluxes in the three types of permafrost regions;The average of CH₄ fluxes in the three types of permafrost regions are?-26.47±189.17?,?118.35±181.76?,?95.52±127.26??g·m^-2·h^-1,continuous permafrost regions manifested as CH₄ sink,discontinuous and island-shaped permafrost regions are the sources of CH₄.The CH₄ flux in the three types of frozen soil area is positively correlated with temperature and negatively correlated with water content.Also,the water content in the soil determines that the permafrost regions is the source/sink of CH₄;The average flux of N₂O in the continuous permafrost region [?-3.90±6.62??g·m^-2·h^-1] is significantly smaller than the island-shaped permafrost region [?3.78±6.15??g·m^-2·h^-1],but the average of N₂O flux in the discontinuous permafrost region [?0.78±6.00??g·m^-2·h^-1] is not significantly different from the continuous and island-shaped permafrost.The difference of N₂O flux in the continuous permafrost region and island-shaped permafrost region is affected by the soil temperature,water content,and TOC.During the observation period,the global warming potentials in the continuous permafrost,discontinuous permafrost and island-shaped permafrost increased in sequence,and CO₂ contributes 96.67% ? 103.26% of GWP,is the main contributor.The freeze-thaw cycle that occurred during the freezing period in autumn did not significantly promote CO₂ flux and CH₄ flux in permafrost regions,but significantly increased N₂O emission flux.Soil temperature and soil moisture have a significant effect on the three greenhouse gases,which can explain the changes of CO₂ emission flux of 14.9% ? 51.8%,64.0% ? 73.2%,CH₄ emission flux change of 51.0% ? 70.3%,83.5% ? 85.4 %,N₂O emission flux change of 60.3% ? 93.3 %,67.6% ? 81.0%.N₂O emission flux is also significantly positively correlated with the contents of NH₄⁺-N and NO₃^--N in the soil.Studies have shown that types of wetlands will not affect the CO₂ and N₂O fluxes,but have a greater impact on the CH₄ flux.In the continuous permafrost,the GWP generated in the autumn freezing period,spring freeze-thaw period,and growing season increases sequentially,and the GWP produced during the freeze-thaw cycle?autumn freezing period and spring freeze-thaw period?is still less than that in the growing season.GWP,the increase in the frequency and duration of the freeze-thaw cycle of the active layer during the permafrost degradation process will not result in an increase in the annual GWP,and the contribution rate of the freeze-thaw cycle during the autumn freeze period to the annual GWP is extremely small.The increase in the frequency and duration of the freeze-thaw cycle of the active layer during the permafrost degradation process will not lead to an increase in the annual GWP,and the contribution rate of the freeze-thaw cycle during the autumn freeze period to the annual GWP is extremely small.Compared with the growing season,the cumulative emissions of CO₂ and CH₄ during the freezing period in autumn are at a low level,and the contribution rates to the total annual emissions of the two greenhouse gases are 2.73% ? 6.56%,-55.12% ? 2.28%,and the N₂O generated during the freeze-thaw cycle has a higher contribution rate to the total annual emissions?30.34% ? 40.50%?.