Forest-fire-scar aging using SPOT-VEGETATION for Canadian ecoregions

The mapping of Canadian fires is a large effort supported by provincial, territorial, and federal agencies. Remote sensing techniques can aid in mapping, especially in remote areas and during busy fire seasons. The SPOT-VEGETATION (SPOT-VGT) sensor has previously shown promise at distinguishing fire scars on the landscape. The usefulness of SPOT-VGT to age fires in 18 Canadian ecoregions was evaluated for a period up to 50 years since fire, analysing more than 250 000 pixels (nominal resolution about 1 km 2 ). The SPOT-VGT reflectances were evaluated using the ratio of the short-wave infrared band (1.58–1.75 µm) to near-infrared band (0.78–0.89 µm), compared with the Canadian large-fire database (fires greater than 200 ha in size). Nonlinear regressions were significant for all ecoregions with r 2 values being greater than 0.57 for 16 of them. Five ecoregions groupings had similar relationships, consistent with their contiguous pattern on the landscape. The prediction of fire-scar age depends on ecoregion and can be successful over periods as short as 6 years to as long as 30 years. The root mean square error for all ecoregions ranged from 5 years for recent burns to about 12 years for three decades following fire. This tool is useful to get approximate fire-scar ages, but the accuracy is limited because of the variation in forest succession on the landscape, and it cannot replace more detailed mapping done currently by fire agencies.