A Method for Rapid Assessment of Historic Fire-Dependent Vegetation Communities
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Date
2006-05-03
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Abstract
In the effort to restore historic landscapes, it is necessary to first specify spatially explicit target vegetation communities. Previously, botanists or other local experts have used landscape and environmental factors, historical evidence, and evidence from remnant vegetation to define presettlement vegetation communities on the landscape. Once these communities are defined, they must be mapped in order to be truly understandable and useful. Efforts to map the location of these presettlement communities on a particular landscape are often laborious and time consuming. In this study, we discuss a rapid method for assessing the location of these vegetation communities using Geographic Information Systems (GIS) and the current science of fire behavior modeling. Fire behavior models are proven predictors of fire intensities across a landscape, considering vegetation, slope, aspect, wind, and weather. Our hypothesis was that these fire behavior models could be used to make inferences about presettlement vegetation community distributions in former frequent-fire landscapes. GIS software was used to find simple combinations of variables associated with vegetation distribution, including soil type, aspect, slope, and orientation to gradient winds. A conventional fire model (FlamMap) was then used to find areas that are distinctly fire sheltered. In a survey of 78 fire sheltered community sites visited on the study landscape, 91% of the areas were considered to be correctly identified based on the presence of remnant presettlement vegetation indicator species. Success in finding a single community as related to a specified range of fire behavior outputs suggests that there is potential for expanded utility of fire models in making inferences about vegetative distribution on the frequent-fire landscape. The fire model adds to the utility of the GIS by considering the effects of fire spread direction and variation in fuel moistures in conjunction with terrain variables. The resulting fire intensity outputs represent environmental effects on vegetation distribution that cannot be modeled solely with a GIS. A final presettlement vegetation layer was completed for the study site, located at Fort Bragg on the Southeastern coastal plain of North Carolina, and compared to a layer generated by an extensive 2-year study considered to be definitive. The results showed an overall map accuracy of 78 percent for the proposed procedure. This output may be used as a preliminary map that, in conjunction with ground-truthing, will shorten the process of mapping presettlement vegetation for use in the restoration of historic fire dependent communities.
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fire, historic vegetation communites
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Degree
MS
Discipline
Natural Resources
