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Scientists Untangle Relationships Among Firing Technique, Fuel Consumption, and Turbulent Transfer in Forests

Photo of A low-intensity backing fire in a pine-oak stand with relatively low fuel loading in 2012, and initiation of a head fire in a pitch pine-scrub oak stand with relatively high fuel loading in 2014. Michael Gallagher and Nick Skowronski, U.S. Department of Agriculture Forest Service.A low-intensity backing fire in a pine-oak stand with relatively low fuel loading in 2012, and initiation of a head fire in a pitch pine-scrub oak stand with relatively high fuel loading in 2014. Michael Gallagher and Nick Skowronski, U.S. Department of Agriculture Forest Service.Snapshot : Forest Service research indicates that relatively low-intensity prescribed fires can be effective at reducing hazardous fuels in forests while minimizing impacts on local air quality.

Principal Investigators(s) :
Clark, Ken 
Research Location : Silas Little Experimental Forest
Research Station : Northern Research Station (NRS)
Year : 2016
Highlight ID : 1124

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.

Forest Service Partners

External Partners

 
  • Exponent, Inc.
  • New Jersey Forest Fire Service
  • University of Edinburgh, United Kingdom

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