Postfire Response of North American Net Primary Productivity Derived from Satellite Observations

Fires influence the carbon cycle through direct emissions of carbon as well as indirect effects on the recovery of ecosystems. In this study we analyzed the impact of fires on net primary productivity (NPP). We used a new, 17-year record of AVHRR satellite observations at 8 km spatial resolution to estimate NPP in North America. We identified fires in the satellite observations using a digitized fire scar data set. We present a case study from a 1991 fire in Quebec; the fire generated a decrease in NPP of 140 g C m-2 yr-1 (60%) after the fire, but NPP nearly recovered after 8 years. An analysis of 61 large fires in the boreal forests of Canada and Alaska revealed that a substantial fraction had NPP decreases immediately following the fire of greater than 100 g C m-2 yr-1 (> 40%). By comparing burned and unburned pixels, we estimated a mean NPP recovery period for boreal forests of about 10 years. The NPP recovery followed an exponential decay curve.