BOREAS flight measurements of forest-fire effects on carbon dioxide and energy fluxes

Fire is the dominant stand-replacing agent in the Canadian boreal forest, b ut few quantitative measurements are available on the micrometeorological e ffects of fire. Airborne flux measurements during the BOREAS experiment wer e referenced to age of burn along a 500-km transect through Saskatchewan an d Manitoba, Canada. These data for 1-, 5-, and 7-year-old burns were supple mented with 15- and 30-year-old-burn data from the BOREAS northern study si te near Thompson, Manitoba. Data were available near midday only and includ ed the June, July and September campaigns during 1994, and July of 1996. Su rface radiometric temperature increased by up to 6 degrees C and remained e levated even 15 years after fire. Net radiation was largely unaffected wher eas albedo decreased in the first year post-fire but recovered by the fifth year. Sensible heat flux increased by 10-20% for the first few years after the fire and then decreased. Latent heat flux slightly decreased after the fire, causing the Bowen ratio to increase by ca. 50% for 7 years post-fire . The CO2 flux was reduced for the 15-year period after fire with the great est reduction to ca. 25% of control areas during the year following fire. H owever, diurnal and annual data are needed to determine the total impact of fire on the boreal-forest carbon balance. (C) 1999 Elsevier Science B.V. A ll rights reserved.