Carbon dioxide evolution from snow-covered agricultural ecosystems in Finland

Abstract

The release of CO2 from the snow surface in winter and the soil surface in summer was directly or indirectly measured in three different soil types (peat, sand and clay) in agricultural ecosystems in Finland. The closed chamber (CC) method was used for the direct and Pick’s diffusion model (DM) method for the indirect measurements. The winter soil temperatures at 2-cm depth were between 0 and 1°C for each soil type. The concentration of CO2 within the snowpack increased linearly with snow depth. The average fluxes of CO2 calculated from the gradients of CO2 concentration in the snow using the DM method ranged from 10 to 27 mg CO2 m2h-1 and with the CC method from 18 to 27 mg CO2 m2h-1. These results suggest that the snow insulates the soil thermally, allowing CO2 production to continue at soil temperatures slightly above freezing in the winter. Carbon dioxide formed in the soil can move across the snowpack up to the atmosphere. The winter/summer ratio of CO2 evolution was estimated to exceed 4%. Therefore, the snow-covered crop soil served as a source of CO2 in winter, and CO2 evolution constitutes an important part of the annual CO2 budget in snowy regions.

Annual CO2 exchange of a peat field growing spring barley or perennial forage grass

“… Koizumi et al [1996] reported CO 2 fluxes of a nearly equal magnitude to ours, about 8 μg CO 2 m −2 s −1 , in practically the same peat soil as ours using the snow gradient and closed chamber method. In agricultural sandy and clay soils the CO 2 production rates were smaller, ranging from 3 to 6 μg CO 2 m −2 s −1 [ Koizumi et al , 1996]. In a peat soil grassland in eastern Finland, clearly higher wintertime emissions of 2.9 g CO 2 m −2 d −1 , equivalent to 34 μg CO 2 m −2 s −1 , have been measured with the chamber technique [ Alm et al , 1999].…”

“…Fluxes from our site were smaller than those measured with a snow gradient method in a sandy loam soil growing barley in Canada, where the respiration rate from the snow‐covered, unfrozen soil ranged from 15 to 78 μg CO 2 m −2 s −1 in February and March 1994–1997 [ van Bochove et al , 2000]. Koizumi et al [1996] reported CO 2 fluxes of a nearly equal magnitude to ours, about 8 μg CO 2 m −2 s −1 , in practically the same peat soil as ours using the snow gradient and closed chamber method. In agricultural sandy and clay soils the CO 2 production rates were smaller, ranging from 3 to 6 μg CO 2 m −2 s −1 [ Koizumi et al , 1996].…”

Winter fluxes of greenhouse gases from snow‐covered agricultural soil:intra‐annual and interannual variations

“…However, these winter CO2 fluxes from barley were higher than those (2.8 to 7.5 [tg CO2 m -2 s 'l) estimated under snow cover from barley plots in Finland [Koizumi et al, 1996]. Interannual variations of CO 2 fluxes do not …”

Bare soil and reed canary grass ecosystem respiration in peat extraction sites in Eastern Finland

“…During the snow covered season in 2004, ecosystem respiration was measured with the snow‐gradient method (Sommerfeld et al, 1993; Koizumi et al, 1996; Alm et al, 1999; Maljanen et al, 2004) from the same sampling locations as those during the snow free period. Gas samples of 20 ml were taken from the depth of 10–20 cm below the snow surface with gas‐tight plastic syringes (Terumo Europe, Leuven, Belgium), attached to a 3.2 mm diameter metal pipe.…”