Efflux of carbon dioxide from snow‐covered forest floors

Abstract

AbstractThe release of CO2 from the snow surface in winter and the soil surface in summer was directly or indirectly measured in four cool‐temperate deciduous broadleaved and evergreen needle forests. The closed chamber method (CC‐method) and Fick's diffusion model (DM‐method) were used for the direct and indirect measurements, respectively. The winter soil temperatures from the soil surface to 10 cm depth were between 0 and 2°C. The concentration of CO2 within snowpack increased linearly with increasing snow depth. The average effluxes of CO2 calculated from the gradients of CO2 concentration in the snow using the DM‐method ranged from 20 to 75 mg CO2 m−2 h−1, while the CC‐method showed the average effluxes of 20 to 50 mg CO2m−2h−1. These results reveal that the snow thermally insulates the soil, allowing CO2 production to continue at soil temperatures a little above freezing throughout the winter. Carbon dioxide formed in the soil can move across snowpack up to the atmosphere. The winter/summer ratio of CO2 emission was estimated to be higher than 7%. Therefore, the snow‐covered soil served as a source of CO2 in the winter and the effluxes represent an important part of the annual CO2 budget in snowy regions.