Fire history of southeastern Glacier National Park: Missouri River Drainage
In 1982, Glacier National Park (GNP) initiated long-term studies to document the fire history of all forested lands in the 410,000 ha. park. To date, studies have been conducted for GNP west of the Continental Divide (Barrett et al. 1991), roughly half of the total park area. These and other fire history studies in the Northern Rockies (Arno 1976, Sneck 1977, Arno 1980, Romme 1982, Romme and Despain 1989, Barrett and Arno 1991, Barrett 1993a, Barrett 1993b) have shown that fire history data can be an integral element of fire management planning, particularly wen natiral fire plans are being developed for parks and wilderness. The value of site specific fire history data is apparent when considering study results for lodgepole pin ( Pinus contorta var. latifolia ) forests. Lodgepole pine is a major subalpine type in the Northern Rockies and such stands experiences a wide range of presettlement fire patterns. On relatively warm-dry sites at lower elevations, such as in GNP's North Fork drainage (Barrett et al. 1991), short to moderately long interval (25-150 yr) fires occurred in a mixed severity pattern ranging from non-lethal underburns to total stand replacement (Arno 1976, Sneck 1977, Barrett and Arno 1991). Markedly different fire history occurred at high elevation lodgepole pine stands on highly unproductive sites, such as on Yellowstone National Park's (YNP) subalpine plateau. Romme (1982) found that, on some sites, stand replacing fires recurred after very long intervals (300-400 yr), and that non-lethal surface fires were rare. For somewhat more productive sites in the Absaroka Mountains in YNP, Barrett (1993a) estimated a 200 year mean replacement interval, in a pattern similar to that found in steep mountain terrain elsewhere, such as in the Middle Fork Flathead River drainage (Barrett et al. 1991, Sneck 1977). Aside from post-1900 written records (ayres 1900; fire atlas data on file, GNP Archives Div. and GNP Resources Mgt. Div.), little fire history information existed for GNP's east-side forests, which are dominated primarily by lodgepole pine. In fall 1992, the park initiated a study to determine the fire history of the Missouri River drainage portion of southeastern GNP. Given the known variation in pre-1900 fire patterns for lodgepole pine, this study was seen as a potentially important contribution to GNP's Fire Management Plan, and to the expanding data base of fire history studies in the region. Resource managers sought this information to assist their development of appropriate fire management strategies for the east-side forests, and the fire history data also would be a useful interactive component of the park's Geographic Information System (GIS). Primary objectives were to: 1) determine pre-1900 fire periodicities, severities, burning patterns, and post-fire succession for major forest types, and 2) document and map the forest age class mosaic, reflecting the history of stand replacing fires at the landscape level of analysis. Secondary objectives were to interpret the possible effects of modern fire suppression on area forests, and to determine fire regime patterns relative to other lodgepole pine ecosystems in the Northern Rockies.