Cold Season CO2 Emission From Arctic Soils

Recent evidence indicates that significant amounts of C may be lost as CO₂ to the atmosphere from tundra ecosystems during the fall, winter and spring months. Because high latitude ecosystems are particularly vulnerable to climate change, and contain large soil C stocks, the annual C budget is of particular interest. Significant amounts of CO₂ loss were observed in arctic tundra ecosystems of the North Slope of Alaska during the 1993–1994 cold season. Moist tussock tundra ecosystems lost approximately 0.3 gC m⁻² d⁻¹ between mid-October and late May while coastal wet sedge ecosystems lost on average 0.08 gC m⁻² d⁻¹. Efflux rates were greatest during the months of October and May when soil temperatures were at a maximum, and portions of the soil profile were unfrozen. These daily loss rates equate to a seasonal loss of roughly 70 and 20 gC m⁻² season⁻¹ for tussock and wet sedge tundra ecosystems, respectively. Combined with warm season estimates of net CO₂ efflux, tussock tundra ecosystems were net sources of approximately 112 gC m⁻² yr⁻¹ (0.1 PgC yr⁻¹ worldwide) over the 1993–1994 calendar year, while wet sedge ecosystems lost approximately 25 gC m⁻² yr⁻¹ (0.02 PgC yr⁻¹worldwide). This study indicates that estimates of annual net CO₂ exchange, based on warm season measurements alone, underestimate the actual magnitude of CO₂ efflux.