Abstract: During the period of 1997-1998, the Dalate Grassland Ecosystem Experimental Station of the Grassland Institute, Chinese Academy of Agricultural Sciences carried out a research project determining soil CO 2 emission and CH 4 uptake fluxes of natural grassland, erected milkvetch grassland, corn field and potato field(the latter three had been reclaimed from the former). Results show that natural grassland, erected milkvetch grassland and upland farm field were all sinks for atmospheric methane.The conversion of natural grassland to farmland increased CO 2 emission from the soil and decreased CH 4 uptake by the soil from the atmosphere. CO 2 emission from the natural grassland and cornfield was in positive linear relationship with soil temperature in 5 cm depth while the CH 4 uptake of the soil was in negative linear relationship with soil moisture.

Key words: CO₂, emission, CH₄, uptake, grassland, greenhouse gases, land use, soil