Estimating release of carbon from forest fires in Alaska using satellite remote sensing data

摘要

While there is little doubt the fossil fuel burning has led to increases in the atmospheric concentration of CO/sub 2/ over the past century, analyses show this increase is significantly less than the total amount of CO/sub 2/ released into the atmosphere through this burning. Studies have shown that other human practices (land clearing and biomass burning) have released significant amounts of carbon into the atmosphere (Houghton 1991). In addition, terrestrial and aquatic biomes act as sources and sinks for atmospheric carbon based upon a complex set of biological, chemical and physical processes. To accurately predict future trends in the rise in atmospheric CO/sub 2/ requires developing a better understanding of the terrestrial and oceanic sources and sinks of carbon. Approximately 4 Pg C yr/sup -1/ are released into the atmosphere during the burning of biomass. In tropical regions Houghton (1991) estimates there is a net release of C to the atmosphere due to burning of biomass in cleared forest lands. When considering biomass burning on a global scale, researchers have discounted the role of fire in boreal forests. However, several oversights were made in these earlier studies. First, the total area burned in boreal forests was significantly underestimated, by as much as an order of magnitude. Second, these initial studies focused on the burning of aboveground biomass, ignoring the large amounts of organic matter in the ground layer that are consumed during fires in boreal forests. Studies have indicated that fires in boreal forests could become a significant source of carbon to the atmosphere over the next half century. Several researchers have demonstrated that low resolution satellite imagery from NOAA's AVHRR system can be used to map and locate fires in Russian and Alaskan boreal forests. In this paper, the authors develop a ground-based model of biomass levels and carbon-release during fires in Alaskan boreal forests to estimate the amounts of carbon released during fire in this region for 1990 and 1991. The authors use the location and areal extent of fires throughout Alaska in 1990 and 1991 derived from AVHRR data.