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Project ID:

24-1-01-15

Year:

2024

Date Started:

09/01/2024

Date Completed:

Title:

Relative effects of mesophication and woody thickening on fuel bed flammability in an oak woodland

Project Proposal Abstract:

Problem Statement. Modern fire exclusion in the eastern United States is believed to have produced oak-dominated forests that are less fire prone than they were previously, with consequences for reduced biodiversity and ecosystem benefits. Two hypotheses have been proposed to explain the observed changes in fuel bed flammability with fire exclusion: “mesophication” and “woody thickening.” Mesophication describes a process in which modern fire exclusion in upland oak-dominated forests has resulted in the replacement and/or mixing of flammable fuels of oaks and pines with less flammable fuels produced by mesophytic trees. Woody thickening describes a process by which modern fire exclusion has converted open woodlands containing a significant grassy component to closed-canopy forests with high tree density and a reduced grassy component. Whereas mesophication appears to reduce fuel bed flammability, the effects of woody thickening on fuel bed flammability are not as clear and may depend on the season in which fire occurs. Both mesophication and woody thickening may be operating simultaneously in oak-dominated ecosystems because fire exclusion has increased overall tree density by increasing mesophyte tree density. To date, the effect of mesophication has not been disentangled from the effect of woody thickening on fuel bed flammability following fire exclusion in eastern US oak ecosystems.
Objectives. In this proposal, I will examine the relative effects of mesophication and woody thickening on fuel bed flammability by testing two hypotheses: 1) Fuel bed flammability in a restored oak woodland during prescribed fires is more strongly affected by tree leaf litter loads than by tree leaf litter species composition and is higher in the late winter than at the end of the growing season, and 2) Fuel bed flammability in a restored oak woodland is related more to a greater abundance of grass in the groundcover (reversal of woody thickening) than to a greater ratio of oak to mesophyte tree leaf litter (reversal of mesophication). To test both hypotheses, I will quantify fuel consumption and fire intensity at different times of the year at Strawberry Plains Audubon Center (Holly Springs, Mississippi). I will test the first hypothesis (fire season and fuel loads) by examining the effects of fire season and tree leaf litter source on fuel consumption and fire intensity in a restored oak woodland. I will test the second hypothesis (grass vs. tree fuels) by examining the effects of fire season, tree leaf litter source, and removal of C4 grasses on fuel consumption and fire intensity in a restored oak woodland. The fire season and fuel loads hypothesis will be supported if fuel consumption (percent fuel consumed) and fire intensity (fire temperature) are greater after fires in late winter than in the late growing season, and this effect is much greater than the effect of tree leaf litter source. The grass vs. tree fuels hypothesis will be supported if fuel consumption and/or fire intensity is lower when C4 grasses are removed than when they are not, and if this effect is greater than the effect of tree leaf litter source.
Benefits. The results will improve our understanding of how modern fire exclusion affects fuel bed flammability and thus the effectiveness of different fire restoration strategies in eastern US oak ecosystems. I will use my unique experience as a female African-American wildland fire fighter and fire ecologist to effectively disseminate my findings broadly to scientists, fire managers, and underrepresented members of these groups.

Principal Investigator:

John S. Brewer

Agency/Organization:

University of Mississippi

Branch or Dept:

Department of Biology

Other Project Collaborators

Type	Name	Agency/Organization	Branch or Dept
Agreements Contact	Renita L Gray	University of Mississippi
Budget Contact	Renita L Gray	University of Mississippi
Student Investigator	Alicia L Arrington-Thomas	University of Mississippi	Department of Biology