Estimating fire-related parameters in boreal forest using SPOT VEGETATION

The majority of burning in the boreal forest zone consists of stand replacement fires larger than 10 km 2 occurring in remote, sparsely populated regions. Satellite remote sensing using coarse resolution (≈1 km) sensors is thus well suited in documenting the spatial and temporal distribution of fires in this zone. The purpose of this study was to investigate the utility of the SPOT VEGETATION (VGT) sensor for estimating three key parameters related to boreal forest fire: burned area, postfire regeneration age, and aboveground biomass. Based on a sample of fires across Canada, the best overall discrimination of burned forest was provided by a normalized short-wave-based vegetation index (SWVI) that combines near-infrared (NIR) and short-wave infrared (SWIR) channels from VGT. Multitemporal differencing of this index from anniversary date VGT composites was combined synergistically with active fire locations from NOAA/AVHRR to map Canadian forest that burned during 1998 and 1999. National burned area estimates for both years were within 15% of those compiled by the Canadian Interagency Forest Fire Centre. The normalized index also was correlated ( R=.68) with the age of regenerating forests in Saskatchewan and Manitoba that burned between 1949 and 1998. An artificial neural network (ANN) model developed using temporal metrics computed from VGT could predict the age of these forests with an RMS error of 7 years ( R=.83). By contrast, forest biomass based on Canada's Forest Inventory (CanFI) was estimated with relatively poor accuracy (RMS=32 tons/ha) from VGT reflectance and terrestrial ecozone using a network model. We conclude that the VGT instrument is effective for mapping large boreal burns at the end of a fire season and approximating the age of regenerating burns less than about 30 years old. This information can be useful to supplement conventional ground-based data sets in remote areas where coverage may be incomplete.