Multi-sensor analysis of the effects of a wildfire in an Alaskanblack spruce forest

摘要

Wildfires play a central role in the ecology of boreal forestsnthroughout the circumpolar region. Fires result in distinct andncharacteristic signatures on all remote sensing imagery. The largenproportion of total area burned in boreal forests occurs in large firenevents-the majority of area burned occurs in fires greater than 10,000nha in size. These fires result in signatures which are not onlynspatially heterogeneous, but also have distinct temporal signatures. Thenauthors present the results of a study which investigated the use of anvariety of systems to monitor the effects of fire on remote sensing datancollected over a large (40,000 ha) forest fire near Tok, Alaska. Thisnfire occurred during the summer of 1991. Visible and near-IR regionn(AVHRR, SPOT) as well the microwave region (the ERS-1 and JERS-1 SARs)nobservations were made. The studies have shown that in the visible andnnear-IR data sets, the remotely-sensed signatures result from variationsnin the levels of burn intensity and patterns of vegetation regrowth.nThese patterns can clearly being interpreted through examination ofnvegetation indices derived from the AVHRR and SPOT data sets. On thenother hand, the analyses of the microwave imagery collected by the ERS-1nSAR show that the spatial patterns of radar backscatter are primarilyndue to variations in surface roughness due to variations in burnnintensity as well as variations in soil moisture, while the temporalnpatterns of radar backscatter are due to seasonal variations in soilnmoisture. The authors present examples of the remotely-sensed data setsnalong with ground-truth measurements which illustrate the sources ofnvariations observed in the satellite imagery