Understanding Historic Wildfire Dynamics in Jasper National Park Using Fire-Scar Dendroecology

English Abstract:

A fire-scar based dendroecological reconstruction of wildfire history was used to detect the influence of climatic variability and land-use change on wildfire dynamics in the lodgepole pine (Pinus contorta var. latifolia Engelm.) forests of Jasper National Park in the Canadian Rocky Mountains. New original analyses were performed on 170 cross-section samples collected in the 1970s from 52 fire history sites from around Jasper, Alberta. The updated fire record reveals that fire occurrence was highly variable such that mean fire return intervals ranged from 4.9 to 52.5 years. Most fires were small and locally occurring. These fires occurred under a wide range of climatic conditions; although the largest and most widespread fires (n=18, events occurring across at least 10% of sites) were primarily driven by dry and warm climate conditions (e.g. El Niño years). Large regional fires burned across almost all sites, although some remnant patches (i.e. sites) remained unburned thus providing evidence for a historically mixed-severity fire regime. Fire activity (i.e. fire size and frequency) decreased through time with fire exclusion becoming widespread during the 1950s. Along with less fire activity on the landscape, there were also shifts in fire seasonality from early human-ignited "spring burns" to more natural lightning-ignited "summer" fires. To be consistent with historic patterns, large-scale restoration via prescribed burning should be scheduled to promote a frequent, patchy, and mixed-severity wildfire regime.