Fire history and vegetation pattern of coniferous forests in Jasper National Park, Albert

Periodicity, location, extent, and severity of fires from 1665 to 1975 were determined for a 43 200-ha area of Jasper National Park using fire-scar dendrochronology. Before fire suppression began in 1913, there were 46 fires with a mean fire return interval (MFRI) of 5.5 years. Twenty-four fires each covered more than 500 ha and had a MFRI of 8.4 years. Fires covering more than 50% of the area had a MFRI of 65.5 years. Present forests originated primarily after the fires of 1889, 1847, and 1758. Most fires between 1665 and 1913 were low to medium intensity, but higher intensities did occur. Interaction of fire periodicity, intensity, and extent determined age, size, density, crown height, and temporal frequency of forest patches. Stands varied from even-age- to multiple-age-classes intermingled over short distances. Multiple-aged stands dominated lower elevations and were maintained by frequent removal, by fire, of low organic matter accumulations. Large, continuous, even-aged forests occurred at mid to high elevations where mesic moisture regimes allowed greater fuel accumulations, and consequently, more intense fires during droughts. Fire periodicity and extent have declined since 1913, accompanied by reduced structural heterogeneity of the forests.