Winter fluxes of CO2 and CH4 from subalpine soils in Rocky Mountain National Park, Colorado

Fluxes of CO2 and CH4 through a seasonal snowpack were measured in and adja cent to a subalpine wetland in Rocky Mountain National Park, Colorado. Gas diffusion through the snow was controlled by gas production or consumption in the soil and by physical snowpack properties. The snowpack insulated soi ls from cold midwinter air temperatures allowing microbial activity to cont inue through the winter. All soil types studied were net sources of CO2 to the atmosphere through the winter, whereas saturated soils in the wetland c enter were net emitters of CH4 and soils adjacent to the wetland were net C H4 consumers. Most sites showed similar temporal patterns in winter gas flu xes; the lowest fluxes occurred in early winter, and maximum fluxes occurre d at the onset of snowmelt. Temporal changes in fluxes probably were relate d to changes in soil-moisture conditions and hydrology because soil tempera tures were relatively constant under the snowpack. Average winter CO2 fluxe s were 42.3, 31.2, and 14.6 mmol m(-2) d(-1) over dry, moist, and saturated soils, respectively, which accounted for 8 to 23% of the gross annual CO2 emissions from these soils. Average winter CH4 fluxes were -0.016, 0.274, a nd 2.87 mmol m(-2) d(-1) over dry, moist, and saturated soils, respectively . Microbial activity under snow cover accounted for 12% of the annual CH4 c onsumption in dry soils and 58 and 12% of the annual CH4 emitted from moist and saturated soils, respectively. The observed ranges in CO2 and CH4 Bur through snow indicated that winter fluxes are an important part of the annu al carbon budget in seasonally snow-covered terrains.