CARBON CYCLING IN THE KUPARUK BASIN - PLANT-PRODUCTION, CARBON STORAGE, AND SENSITIVITY TO FUTURE CHANGES

The Marine Biological Laboratory General Ecosystem Model was calibrate d for an arctic tussock tundra system using data from long-term observ ations and experiments at Toolik Lake, Alaska. These experiments inclu de the effects of changes in temperature, light, CO2, and nutrients, s o the model could be applied to five regions comprising the entire Kup aruk River basin. Met primary production, averaged for the entire basi n, was 92 g C m(-2) yr(-1). A 150 year simulation of carbon storage un der a doubling of CO2 (slow ramp-up) and a temperature increase of 3.5 degrees C gave an estimate of +400 g C m(-2) when soil moisture incre ased and +500 g C m(-2) when soil moisture decreased. Drier soils stim ulated decomposition producing an increase in nitrogen availability; t he increased N led to increased net primary production. If this result is applicable to other arctic ecosystems, then it is unlikely that wa rming will enhance carbon loss to the atmosphere to further enhance wa rming.