Summary
Knowing how firing practices and the resultant fire behavior control the consumption of forest fuels is important for “fine tuning” the effectiveness of fuel reduction treatments. To better understand the relationships between firing practices, consumption of specific fuels, and above-canopy turbulence and energy exchange, Forest Service scientists studied eight prescribed fires ranging in intensity from low-intensity backing fires to high-intensity head fires in the New Jersey Pinelands. The scientists used pre- and post-burn destructive sampling to quantify surface fuels on the forest floor and in the understory, Light Detection and Ranging, or LiDAR, remote sensing data to quantify canopy fuels, and a network of above-canopy towers instrumented with sonic anemometers and meteorological sensors to measure turbulence and energy exchange. Fuel consumption was strongly related to initial fuel loading, and above-canopy heating was significantly correlated with fire-generated turbulence. Surprisingly, there was little relationship between surface fuel consumption and heat exchange or fire-generated turbulence. The relatively long residence times of flame fronts during low-intensity backing fires contributed to their effectiveness in reducing surface fuels. Results indicate that while intense head fires are necessary to reduce crown fuels, low-intensity fires are highly effective at consuming surface fuels and minimizing the adverse impacts of ember transport and smoke dispersion on local air quality.
