Fire Research » Fire Ecology & Fire Effects

Fire Ecology and Fire Effects

BORFIRE - Boreal Fire Effects Model

The Boreal Fire Effects Model (BORFIRE) was developed to study the effects of future altered fire regimes on the boreal forest. As a result of climate change, future fire regimes are expected to show a general increase in fire intensity, fire severity (depth of burn), and fire season length. Change in the fire regime is also expected to have an effect on the forest disturbance rate or annual area burned. Because of differences in fire survival and postfire regeneration strategy, a change in the future fire regime will favor some tree species over others and could cause a shift in forest composition. This could in turn affect carbon sequestration rates through the different growth rates of tree species. Biomass (or fuel) dynamics also have a feedback effect on fire regime through flammability and fuel load, which affect fire occurrence and intensity. BORFIRE was developed to simulate the interactions between physical fire parameters and the fire ecology of boreal tree species.

BORFIRE quantitatively simulates tree community dynamics (species composition, stand density, and average tree height and diameter) and biomass dynamics (above- and below-ground, live and dead organic material) for six major boreal tree species: black spruce (Picea mariana), white spruce (Picea glauca), jack pine (Pinus banksiana), trembling aspen (Populus tremuloides), white birch (Betula papyrifera) and balsam fir (Abies balsamea). Changes in tree community and biomass conditions are based on processes of tree mortality, tree recruitment, tree growth, biomass decomposition, and biomass consumption by fire (see diagram below). Fire, climate, and competition drive the model processes. Tree community dynamics are driven by fire disturbance events, which affect recruitment and mortality, and by natural thinning due to intra- and inter-specific competition within the stand. Biomass component values are the product of species composition, stand density, and accumulation of dead organic matter. Biomass increases with tree growth and decreases with decomposition of dead organic material and fuel consumption during fire. The model is process-driven, uses an annual time-step, and simulates conditions at the stand level.

BORFIRE has been applied to four national parks in the Prairie Region using climate data output from the Canadian Global Coupled Model (CGCM). Climate data for present (1975–1990) and future (2080–2100) conditions were used to calculate fire weather and component values of the Canadian Forest Fire Weather Index System. These were then used to calculate fire behavior (head fire intensity, depth of burn, fuel consumption, rate of spread) for simulated fires. Overall, shorter fire cycles and higher fire severity in the model simulations resulted in a shift toward more Populus tremuloides, which resprouts quickly after fire, and less Picea glauca, which regenerates poorly after fire. Total biomass storage also tended to increase because of faster growth rates in Populus tremuloides.

Spatial landscape applications of BORFIRE are in progress, including additional climate change studies and real-time applications for fire management.