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Fire Mgmt. Policy
Fire and Park Resources
Annual Fire Reports
Fire Frequency Analysis of Sierra Forests
Don C. Erman
Department of Wildlife, Fish, and Conservation Biology
and
Centers for Water and Wildland Resources
University of California
Davis, California
Russell Jones
Sierra Nevada Ecosystem Project
Centers for Water and Wildland Resources
University of California
Davis, California
Current address:
P0. Box 4226
Evergreen, CO 80437
ABSTRACT: The pattern and frequency of fire size reported for seven national forests and Sequoia-Kings Canyon National Parks were assessed by frequency analysis, a method commonly used in hydrology for establishing probabilities of future events from historical data. The common generality that throughout the Sierra frequently occurring fires have become smaller and infrequently occurring large fires are becoming larger is not supported by the data. In the Plumas and Sequoia National Forests size and frequency of fires have not changed significantly during this century; in the Sierra National Forest all fires were larger before 1950; in Sequoia-Kings Canyon National Parks frequent small fires have been larger since 1950, and infrequent large fires have been smaller since 1950. The pattern of smaller; frequent fires and larger; infrequent fires since 1950 was true, however, in the central-western Sierra, in the Eldorado and Tahoe National Forests, and - to a lesser extent - the Stanislaus National Forest and the Lassen National Forest. Since 1950 in the Eldorado National Forest, frequent fires (those with recurrence intervals from 2 to 5 years) were 70%-80% smaller than before 1950, and infrequent large fires (with recurrence intervals from 10 to 40 years) were 250%-500% larger than before 1950. The average fire for all forests (taken as approximately the size at a 2-year recurrence interval) ranged from about 350 acres to 1500 acres (142 to 607 hectares), illustrating the variation throughout the Sierra. There was large variation in diligence of fire data collection among the national forests and national parks, ranging from forty-eight years (Lassen National Forest) to seventy-nine years (Stanislaus and Sequoia National Forests) of record. With additional data other applications of frequency analysis may be useful in examining the patterns of fire on the landscape. By recognizing that fire patterns differ throughout the Sierra, we can begin to dispassionately examine causes of fire.
