Identifier

etd-05312013-085359

Degree

Doctor of Philosophy (PhD)

Department

Biological Sciences

Document Type

Dissertation

Abstract

Fire is an essential process for maintaining pine-dominated ecosystems in the southeastern United States. Fire opens space for pine recruitment, consumes fine fuels, stimulates flowering of herbaceous plants, and topkills woody plants. Topkill is the death of the aboveground portion of the plant, which does not necessarily lead to mortality. Most of the woody species in these ecosystems are able to resprout following topkill, sprouting new shoots from meristems at the base of the plant. In the absence of fire, pine-dominated ecosystems transition to closed canopy hardwood forests. Prescribed fires can be applied to mimic the historical fire regime, but the selected time since fire, season of burn, and ignition techniques used can influence both fire characteristics and the response of vegetation. In this dissertation, I explore the effects of prescribed fire treatments on fire characteristics and hardwood resprouting by applying prescribed fires to plots in a shortleaf pine-oak-hickory woodland in north Florida. Fireline intensity, residence times, and heat released per unit area increased progressively with longer time since fire treatment. Reaction intensity, on the other hand, decreased with time since fire, attributable to increased fuel bulk density. Fireline intensity was dampened by greater fuel moisture in the growing season and was greatest with head fire ignitions. I evaluated the response of hardwoods to prescribed fires using a path analysis model. The results of this model suggest that one-year post-fire biomass is mediated via the size and root reserves at the time of topkill, while the characteristics of the fire do not have an effect. I conducted a shadehouse experiment to test for the effects of season and method of topkill on hardwood genets. Genets topkilled in the growing season had reduced resprouting biomass compared to topkill in the dormant season. There was not a difference in biomass between burned and clipped plants. The results of this study suggest that the response of hardwoods to fire in savanna ecosystems is mediated by the size and resource allocation of plants rather than the intensity of fires.

Date

2013

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Platt, William J

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