Early and late winter CO2 efflux from arctic tundra in the Kuparuk River watershed, Alaska, USA

Large amounts of soil carbon and sensitivity of arctic ecosystems to climate change is leading to increased interest in the spatial and temporal variability of CO2 release from arctic tundra during winter. The purpose of this research was to quantify early and late winter CO2 efflux along a 200-km transect of the Kuparuk River drainage in northern Alaska, from the foothills of the Brooks Range to Prudhoe Bay. Measurements were made in November 1996 and April 1997 at 25 sites which encompassed four broad tundra types, including upland tussock tundra, water tracks, tall willow riparian, and coastal plain tundra. Carbon dioxide concentrations within the snowpack were measured using a portable infrared gas analyzer, and conservative CO2 efflux estimates were calculated using a steady-state diffusion model. Mean CO2 efflux in November was 204, 314, 359, and 527 mg CO2 m(-2) d(-1) for tall willow riparian, upland tussock, coastal plain, and water track tundra, respectively, while in April means were 70, 82, 96, and 203 mg CO2 m(-2) d(-1). Snow depth and temperature exhibited no direct relationship with CO2 loss, suggesting that winter CO2 efflux from arctic tundra is controlled by additional mechanisms. Our measurements are the most spatially extensive yet made in arctic tundra.