Date of this Version
Final Report: Joint Fire Science Program Project 09-1-01-7
We completed an investigation of the long term legacies of fuels treatments in longleaf pine sandhills at Eglin Air Force Base in the panhandle of Florida. From 1994-1999, The Nature Conservancy conducted a large-scale, long-term study at Eglin Air Force Base to compare the effectiveness of midstory reduction treatments, including herbicide, growing season fire, and mechanical clearing on the restoration of longleaf sandhill pine forests. The study plots have been monitored continuously since the completion of the original study and information still exists for all experimental sites, which have been burned as part of the prescribed fire program at Eglin AFB since the study concluded. We examined the legacy of these treatments on fire behavior 15+ years later in these plots. We measured multiple aspects of fuels and fire behavior in a subset of the original plots using a combination spatially explicit fuel sampling, high resolution visual and thermal imagery, wide and narrow field of view radiometers, thermocouples and thermopiles to collect data on fuel type, fuel loading, radiant and convective heat fluxes. We collected data in nine large operational prescribed fires that included the treatment plots in 2011. Preliminary data analyses showed that the impact of the treatments was not detectable in our measurements. The occurrence of frequent low intensity fires in the treatments appeared to have driven a convergence of fuel characteristics in plots with and without management interventions in as little as 16 years. Within stand variation in overstory derived fuels appeared to be more important in explaining fire behavior than the original treatments. We also completed an investigation of heat transfer in midstory oak stems. While these results are still being analyzed we found that in species with rough bark, heat transfer is much more complex and necessitates the consideration of three-dimensional information on bark topography and surface heating to develop accurate tissue damage models. The data we have collected will allow us to make those improvements. We also have developed a promising means (photogrammetry coupled with IR imagery) to rapidly capture the fine scale surface topography and heating of stems useful for improving such models.
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