U.S. Joint Fire Science Program


Date of this Version


Document Type



Project Number: 09-1-01-2


US government work.


Land managers in the southeastern United States (U.S.) have actively used prescribed fire, primarily in the winter or dormant season, as a tool to control the growth of understory vegetation since the middle of the last century. There is evidence, however, that burning during the growing season may have different, and in some cases more desirable effects on ecosystem processes, vegetation structure, vegetation composition and, by virtue of these factors, understory fuels and potential fire behavior. We conducted an experiment to document and test for potential differences in the rate of fuel re-growth and accumulation following prescribed fires during the dormant and growing seasons. In other words, as a fuel management treatment, do growing season prescribed fires have a different lifecycle than dormant season prescribed fires? We tested the hypotheses that fuels re-grow and accumulate more slowly following growing season fires, and that growing season fires change the structure and composition of the understory fuelbed to a larger degree when compared to dormant season fires. Our study measured fuel amount and composition annually following dormant and growing season prescribed fires for approximately two years in longleaf pine (Pinus palustris) flatwoods ecosystems in western (Eglin Air Force Base) and north-central (Apalachicola National Forest and St. Marks National Wildlife Refuge) Florida. We attempted to confirm anecdotal observations that fuel reduction that results from growing season burns lasts longer and also that the structure and composition of the post-fire fuelbed differs between growing season and dormant season fires. Confirmation of these observations could allow fire managers to adjust the intervals between fuel-reduction burns for the landscapes they manage, enabling treatment of more area for the same amount of effort and expense. As well, results from this study could suggest which treatments are most effective for restoring the structure and composition of understory fuels in flatwoods communities that have experienced a departure from desirable, historical conditions. Prescribed fires at our managed, mesic longleaf pine flatwoods sites maintained reduced shrub and herbaceous fuel loading, coverage and height at least two years post-fire. Our experiment showed very little difference in post-fire fuel dyanamics related to season of burn, although the temperature of the fire did appear to affect shrub regrowth, with hotter fires producing a larger and longer-lasting reduction in shrub loading and coverage. We observed differences in post-fire fuel dynamics between the western and north-central Florida study regions and suspect those differences are related to regional variations in species composition.