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Yellowstone National Park Report

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Fire is now recognized as a major ecosystem process and Yellowstone National Park has recently implemented a fire management plan that permits lightning fires to burn without interference under certain conditions. To predict the kinds of wildfires we can now expect in the Park, and to evaluate the effectiveness of this plan in restoring fire to the Yellowstone ecosystem, it is important to know the natural frequency and size of wildfires under pristine conditions. This study, which began in 1977 and was completed in August 1979, had the following objectives: (1) to determine the incidence and size of major fires during the last 300-400 years on the 73-km2 Little Firehole River watershed, an area dominated by extensive lodgepole pine and some spruce-fir forests; (2) to determine average fire frequency, i.e., the time interval between successive major fires on any particular sites; (3) to determine the relationships between stand age or successional stage and fuel accumulation or the probability of fire; and (4) to examine the effect of fire on patterns of landscape diversity. Three components of landscape diversity were recognized - richness, evenness, and patchiness. Richness is simply the number of different community types represented, while evenness is an expression of the proportion of the landscape covered by each community type (maximum evenness occurring when every type occupies an equal area). The patchiness component is based on the size and interspersion of the community types.