Effects Of Simulated Climate Change On Greenhouse Gas Fluxes In Typical Steppe Ecosystem

Climate change,mainly in the form of warming and precipitation changes,has become a hot issue concerned by the international community.The increasing greenhouse gases in the atmosphere such as carbon dioxide?CO₂?,methane?CH₄?and nitrous oxide?N₂O?leads to the greenhouse effect,the main causes of global warming.As an important part of terrestrial ecosystem,grassland regulate the concentration of greenhouse gases in the atmosphere by the emission and absorption processes of carbon dioxide?CO₂?,nitrogen oxide?N₂O?and methane?CH₄?.Therefore,exploring the effects of increased temperature and precipitation on greenhouse gas flux and soil nutrient content is important to reveal the feedback of typical steppe to climate change.This study has great scientific significance for predicting the greenhouse gases budget of grassland ecosystem.In this study,warming and precipitation increased experiments were carried out in Xilingol typical steppe of Inner Mongolia from 2017 to 2018.The Open Top Chamber?OTC?was used to simulate warming.We set four treatment:Control?CK?,T?Warming?,Precipitation?P?,TP?Warming and Precipitation?.The regularity of greenhouse gases flux and the dynamics of soil nutrients in typical grasslands were measured.And the responses of greenhouse gas emissions to warming and precipitation increased were analyzed.The main results were as follows:1.Warming and precipitation increased had different effects on soil nutrients.Precipitation increased soil total nitrogen content by 22.7%.The proportion of NH₄⁺-N increased significantly by 52.0%in T and 24.9%in TP.NO₃^--N content increased by 139.7%in P and 73.3%in TP.The carbon content of microbial biomass increased by 53.8%in TP.The microbial biomass nitrogen increased by 17.3%and 41.9%respectively by P and T.The content of dissolved organic nitrogen increased by 33.1%with TP.There was no significant difference in the content of soil total carbon and soluble organic carbon between different treatments.2.Typical steppe soil is source of CO₂ and N₂O and sink of CH₄.Flux of each greenhouse gas was higher in growing season.In growing season,the CO₂ fluxes was ordered as follows:P>TP>CK>T.The CH₄ fluxes were ordered as follows: T>CK>TP>P.And the N₂O flux were ordered as follows:P>TP>CK>T.3.Soil temperature and moisture are the main factors affecting soil CO₂,CH₄ and N₂O fluxes.Soil CO₂ flux was positively correlated with soil temperature and moisture ?P<0.05?,with explanation ratios of 64.47%and 13.17%,respectively.CH4 was positively correlated with temperature,N₂O flux was positively correlated with soil moisture?P<0.05?,and the explanation ratios were 51.2%and 8.4%respectively.4.As a representative of typical steppe greenhouse gases,CO₂ emissions account for more than 90%of the total emissions of the three greenhouse gases.Variations in temperature and moisture make the contribution of different greenhouse gases to total emissions inconsistent.The contribution of CH₄ to total emissions in typical grasslands was higher than that in the control,and the contribution rate of CO₂ emissions increased with the increase of rainfall.The proportion of N₂O in total emissions is small,and its contribution rate has no significant difference among different treatments.