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 climat e change is leading to increased interest in the spatial and temporal varia bility 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 t ransect of the Kuparuk River drainage in northern Alaska, from the foothill s of the Brooks Range to Prudhoe Bay. Measurements were made in November 19 96 and April 1997 at 25 sites which encompassed four broad tundra types, in cluding upland tussock tundra, water tracks, tall willow riparian, and coas tal plain tundra. Carbon dioxide concentrations within the snowpack were me asured using a portable infrared gas analyzer, and conservative CO2 efflux estimates were calculated using a steady-state diffusion model. Mean CO2 ef flux in November was 204, 314, 359, and 527 mg CO2 m(-2) d(-1) for tall wil low riparian, upland tussock, coastal plain, and water track tundra, respec tively, while in April means were 70, 82, 96, and 203 mg CO2 m(-2) d(-1). S now depth and temperature exhibited no direct relationship with CO2 loss, s uggesting that winter CO2 efflux from arctic tundra is controlled by additi onal mechanisms. Our measurements are the most spatially extensive yet made in arctic tundra.