CH_4 and N_2O dynamics of a Larix gmelinii forest in a continuous permafrost region of central Siberia during the growing season

摘要

Forest soils are generally sinks of CH_4 and sources of N_2O. 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 CH_4 and N_2O fluxes and forest floor vegetation types, soil temperature, and moisture conditions. At the soil surface, both CH_4 uptake and emission (-6.6 to 3.1 μg CH_4-C m~(-2) h~(-1)) were observed, and CH_4 fluxes did not differ among vegetation types. CH_4 flux was positively correlated with soil moisture, but not with soil temperature. The small CH_4 uptake compared with previous reports was due to CH_4 production in response to high precipitation. N_2O was also emitted and taken up by soil (-0.2 to 0.4 μg N_2O-N m~(-20 h~(-1)), and N_2O fluxes did not differ among vegetation types. N_2O 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 N_2O uptake due to denitrification. Furthermore, both CH_4 and N_2O were emitted from a river at the site; these were produced in the basin of the riverbank rather than deep in the soil.