Fine-scale mapping of presettlement fire regimes and vegetation: A new approach

The presettlement United States was a fire landscape.  Fire suppression and altered grazing and browsing regimes have changed the structure of natural communities and placed hundreds of species of native plants and animals in danger of extinction.  Spurred by the need for restoration of fire-suppressed landscapes, methods are being developed for fine-scale mapping of pre-European fire regimes and the vegetation they supported.  Until now fine-scale methods have been lacking but these are precisely what is needed in order to manage reintroduction of fire to specific sites.  A method is presented here which combines principles of landscape fire ecology, field sampling data and historical information to make fine-scale maps of original fire and vegetation.  Using this method, both presettlement vegetation and fire regimes are reconstructed simultaneously.  Landscape activities include mapping original fire compartment sizes and evaluating fuels, firebreaks, bottlenecks and fire filters.  Field methods include sampling remnant natural vegetation, determining its successional trajectory under fire suppression on each soil type, and recording effects of fire on good reference sites for each soil series and each slope and aspect.  Historical methods include fire scar chronologies if available, and ranking historical boundary line survey trees and other vegetation by their fire relations and then using them to statistically test the accuracy of the semifinal map.  Since soil maps are used as a starting point for putting boundaries on vegetation, the final unit of scale is something approximating the soil pedon.  This produces a fine-scale map, with a resolution sufficient for setting restoration targets for the smallest unit of land management.