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Document Type

Bighorn Canyon National Recreation Area

First Page

29

Last Page

29

Abstract

A landscape approach was used to study fire history and fire behavior in the Douglas-fir forests and foothill vegetation of the Bighorn Canyon National Recreation Area in southcentral Montana. The 3,976 ha study area was divided into 4-ha grid cells, and traditional fire scar analysis and fuel sampling methods were used for data collection in each cell. There have been 15 surface fires during the last 109 years and 10 canopy fires during the last 360 years. The mean fire interval in the forests as a whole, was 7 years for surface fires and 31 years for canopy fires. Using the Weibull function, the recurrent time for fire in a specific grid cell was 212 and 226 years for surface and canopy fires, respectively. The distribution of the probability density function showed that there was a peak of high canopy fire frequency between 150-250 years of stand age. There was no obvious peak period for surface fires in humid ravines, which suggests that surface fires there are not associated with aging. Employing Rothermel's model, a fire behavior model (FIREMDL) was developed and linked it to a geographic information system (GRASS) to simulate flammability of each grid cell under different conditions of fuel moisture and wind velocity. The results suggest that flammability is highly variable because of differences in vegetation and topographic position.

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