Effects Of Warming On Soil Carbon Dioxide?Methane Emissions And Generation Mechanism In Antarctica

Antarctica is far away from human activities and has a simple ecological structure,so it is sensitive to climate change.Recently,a growing number of studies indicate that Antarctica has gradually become an important source of greenhouse gas emissions,especially in coastal marine animal colonies.Although several reported studies focus on the greenhouse gas fluxes in the Antarctic,the impact of temperature changes on greenhouse gas emissions remains poorly understood.Under global warming scenarios,it remains unclear how soil greenhouse gas emissions respond to temperature change in Antarctica.The main study areas were located on Fildes Peninsula,Ardley Island and Mile Peninsula.We set the temperature and water gradient according to the actual temperature change range and water input after ice melting,and used indoor constant temperature incubation combined with carbon dioxide(CO₂)isotope instrument and methane(CH₄)isotope instrument to determine the emissions of CO₂ and CH₄ and the change of carbon isotope in Antarctic soils.We analyzed the contribution ratio of var-ious sources of soil organic carbon(TOC)in penguin colonies and the change of carbon and nitrogen contents in Antarctica soils,and revealed the characteristics of soil CO₂and CH₄ emissions.We elucidated the effects of temperature and water conditions on CO₂and CH₄emissions as well as influencing factors.The main contents and results are as follows:(1)Compared with bare soil area and tundra region,the content of soil carbon and nitrogen(total organic carbon and ammonia nitrogen)in penguin colony was the high-est.In the penguin colony,penguins transport a large number of C and N sources to the soil through excreta,resulting in a high content of soil carbon and nitrogen.Due to the mineralization of soil organic matter,the contents of TOC and NH₄⁺-N in the bare soil areas and tundra regions decreased as a whole,while the contents of TOC and NH₄⁺-N in the penguin colony increased at first and then decreased in the three temperatures incubation periods.In this article,a three-end-member mixing model was used to trace the source of soil organic carbon in the penguin colonies of Ardley Island,Antarctica.The soil organic carbon mainly come from marine(penguin dung),and the average contribution rate was 58.13%;the average contribution rates of terrestrial vegetation and terrestrial soil accounted for 19.39%and 22.48%.The intensity of the penguin col-ony affected the source of soil organic carbon.Penguins in the eastern of Ardley Island acted frequently,and the proportion of marine was more than 70%;while penguin col-onies in the western of Ardley Island were sparse,and the proportion of marine was only near 50%.(2)The emissions of CO₂ and CH₄ from different types of soils had spatial differences,the penguin colony soil was an important source of CO₂ and CH₄ emissions.Compared with other types of soils,the penguin colony soils showed the highest CO₂ and CH₄emissions with the lowest value in the bare soil area.Therefore,the penguin colony is an important emission source of CO₂ and CH₄ in Antarctica.Through correlation anal-ysis showed that CO₂ fluxes in Antarctica soils was significantly positively correlated with Mc,TOC,NH₄⁺-N and NO₃^--N(R~2=0.75,R~2=0.79,R~2=0.65,R~2=0.95,p<0.01),and CH₄ fluxes in Antarctica soils was significantly positively correlated with Mc,NH₄⁺-N and PO₄^3--P(R~2=0.42,R~2=0.82,R~2=0.96,p<0.01).(3)Temperature changes affect CO₂ and CH₄ emissions from Antarctic soil.The responses of CO₂ and CH₄ emissions from different types of soils in Antarctica to tem-perature rising were different.The increased temperature can promote soil CO₂ emis-sions in the bare soil areas,but too high temperature(10?)reduced soil CO₂ emissions fluxes in the tundra regions and penguin colonies.It was mainly related to the temper-ature range adapted by microorganisms.There were many cold loving and cold resistant microorganisms,and the excessive temperature increase inhibited their activity.Under incubation at 5?,The average CO₂ emission fluxes from the bare soil areas,tundra regions and penguin colonies increased by 0.68%,45.55%and 228.74%compared with incubation at 1?.Under incubation at 10?,the average CO₂ emission fluxes from the bare soil areas increased by 17.72%,and that of the tundra regions and penguin colonies decreased by 2.79%and 3.41%compared with incubation at 5?.The bare soil area and tundra region were the sinks of CH₄,the penguin colony was the source of CH₄.The CH₄ fluxes from each type of soils were the highest at 5?.The increased temperature(10?)decreased the CH₄ uptake fluxes from the bare soil areas and tundra regions by 57.98%and 80.77%,the emission fluxes from the penguin colonies de-creased by 69.06%.In general,too high temperature(10?in this experiment)will inhibit soil CO₂ and CH₄ emissions in Antarctica.(4)Water was also another important factor affecting the emissions of CO₂ and CH₄from Antarctic soil.The responses of CO₂ and CH₄ emissions from different types of soils in Antarctica to water addition were different,and the soils in penguin colony were more vulnerable to water addition.Under three temperatures incubation,the emissions of soil CO₂ and CH₄ in the penguin colonies increased with water addition.At 5?,the CO₂emission fluxes from bare soil areas and tundra regions increased with water addi-tion;at 1?and 10?,the CO₂ emission fluxes from the bare soil areas and tundra regions decreased with water addition.The effect of different water additions on soil CH₄ fluxes in the tundra regions was not obvious.Generally,CH₄ fluxes increased slightly with water addition at three temperatures incubation.At 1?and 5?,the CH₄uptake fluxes from the bare soil areas increased with water additions;at 10?,the CH₄uptake fluxes from the bare soil areas decreased with water additions.