Tuesday, 18 November 2003: 11:00 AM
The peripheral reduction in burn probability around recent burns in the boreal forest
This study examines the spatial relationship between large recent burns and their effect on the probability of burning in the western boreal forest of Canada. The burn probability (BP) provides an estimate of the present likelihood that a given point (e.g., cell) on a landscape could experience a fire. BURN-P3 (probability, prediction, and planning) is a landscape fire model combining the physical components of fire spread through fire growth modeling and other probabilistic aspects of the fire regime (e.g., number of fires, locations of ignition, weather) in a re-iterative process. It was used to produce BP maps for multiple scenarios in which the change in BP around large fires of different sizes and shapes was analyzed in both homogeneous (control) and heterogeneous (actual) landscapes under historical burning conditions. Results demonstrate that recent burns of all sizes reduced the BP all along a fire’s periphery, although the width of this zone is highly variable in heterogeneous landscapes. This spatial variation is a result of (1) different forest fuels, (2) the amount and configuration of landscape features, such as lakes, and (3) the direction of predominant winds. A proportionally greater overall reduction of BP around the largest burns was observed, as these larger burns become more effective at disrupting the paths of incoming fires. It is well known that recent burns in the boreal forest are largely unlikely to re-burn for a number of years; however, we present evidence that the likelihood of burning can also be reduced for distances far beyond the perimeter of these burns.