An Investigation on the Relationship Between Emission/Uptake of Greenhouse Gases and Environmental Factors in Semiarid Grassland

Measurements of greenhouse gases CO2, CH4, and N2O were made by static chamber-gas chromato-graph in Inner Mongolia. Results indicate that with growing seasons, the daily variation patterns ofemission/uptake of greenhouse gases differ greatly in the prairie ecosystem. The peak of seasonal emis-sion/uptake of three greenhouse gases occurs at the melting period in spring when soil moisture is highand rainfall is rich. The daily emissions of CO2 from steppe vegetation in growing seasons are low duringthe daytime and high at night. Higher temperatures are advantageous to emission of CO2, as abovegroundbiomass determines the amount of CO2 photosynthetic uptake. The key factors that influence the dailyvariation patterns of CH4 uptake and N2O emission in semiarid grassland are soil moisture and the oxygensupplying condition, while the changes in daily temperature mainly affect the range of daily variations.The seasonal changes of N2O emission are positively related to seasonal change in soil moisture. Freegrazing reduces the daily mean deviation of exchange rates of CO2, N2O, and CH4, but it decreases theamount of annual emission/uptake of N2O and CH4 yet it increases the annual emission of CO2.