Studies of Methane Production and Emission in Relation to the Microrelief of a Polygonal Tundra in Northern Siberia

Abstract

Methane production and emission in a polygonal tundra on Taimyr Peninsula in North Siberia (75°N, 98°E) were investigated during summer 1996. The in situ methane emission was measured several times per day between July and September at a typical polygonal tundra site. Additionally, measurements were carried out at different plots along a transsect through the investigated valley to determine the variability of methane emissions of the whole polygon area. CH4 emission rates showed high response on microrelief, which influences water table and soil temperatures. No diurnal variations in methane emissions were found. The emission rates ranged from 0-160 mg CH4-d-1-m-2. Based on detailed mapping of soils and surface structures (patterned grounds) a projection on total methane emission from the investigated polygonal tundra is possible. The mean daily emission rate between July and September is about 50 mg CH4*d-l*-m-2, which is about 4% of total gaseous carbon loss from soil to atmosphere. Isotope investigations proof the reduction of CO2/H2 to be the major pathway of methane production and fermentation being negligible. At the end of the thawing season methane emissions and methane content of the pore water decrease. Methane oxidation is very effective even when the water table is only a few centimeters below the surface.