Over a half year from May 22 to December 11, 1997, We made measurements of the fluxes of methane and carbon dioxide by closed chamber techniques from 6 sites in Tukigaumi Marsh, Hokkaido, Japan. And besides, we collected and analyzed pore water and soil samples. The measured methane fluxes exhibited no daily trend, however, showed significant seasonal variations with Summer-Autumn maximum. Emissions from Tukigaumi Marsh averaged 0.8 mg-CH4/ m2h ranged from 0.6 to 1.3 mg-CH4/ m2h at Site-A. On the other hand, measured carbon dioxides fluxes showed remarkable daily and seasonal variations. The measured methane fluxes did not depend on groundwater levels and atmospheric temperature but slightly depended on soil temperature in the deep layer. Evapotranspiration processes by plants and oxidization processes by methanotrophs were not considered to affect the methane emissions from the marsh. Dissolved methane concentrations in the water, methane production potentials and number concentrations of methanogens increased with depth from the surface to 4 m depth, so that the methane emissions supposed to be controlled by the conditions at the deep layer of Tukigaumi marsh.
