CH4 and N2O dynamics of a Larix gmelinii forest in a continuous permafrost region of central Siberia during the growing season

Abstract

Forest soils are generally sinks of CH4 and sources of N2O. To characterize the dynamics of these major greenhouse gases in central Siberia during the growing season, we measured fluxes from forest soil and assessed the relationships between CH4 and N2O fluxes and forest floor vegetation types, soil temperature, and moisture conditions. At the soil surface, both CH4 uptake and emission (−6.6 to 3.1 μg CH4–C m−2 h−1) were observed, and CH4 fluxes did not differ among vegetation types. CH4 flux was positively correlated with soil moisture, but not with soil temperature. The small CH4 uptake compared with previous reports was due to CH4 production in response to high precipitation. N2O was also emitted and taken up by soil (−0.2 to 0.4 μg N2O–N m−2 h−1), and N2O fluxes did not differ among vegetation types. N2O flux was negatively correlated with soil moisture and not correlated with soil temperature. Our findings suggest that high soil moisture and low availability of mineral nitrogen resulted in N2O uptake due to denitrification. Furthermore, both CH4 and N2O were emitted from a river at the site; these were produced in the basin of the riverbank rather than deep in the soil.