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A Multiproxy Reconstruction of Mixed-severity Wildfire Dynamics in the Foothills of the Rocky Mountains, Alberta, Canada

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Title: A Multiproxy Reconstruction of Mixed-severity Wildfire Dynamics in the Foothills of the Rocky Mountains, Alberta, Canada
Author: Stretch, Vanessa
Department: Department of Geography
Program: Geography
Advisor: Gedalof, Ze'ev
Abstract: Fire history reconstructions are key to contextualizing the recent and future impacts of humans and climate on changing wildfire regimes. The eastern Foothills of the Rocky Mountains in west-central Alberta, Canada, represent an ecotone between the montane cordillera and the boreal plains. While fire regimes of both biomes have been historically described as infrequent and high-severity, recent fire history studies in the montane cordillera have found historical evidence of mixed-severity fire regimes. The broad aim of this research was to reconstruct and contextualize the historical wildfire regime of this transitional landscape. Modern wildfire records are often limited in length and may be misrepresentative of the natural disturbance regime due to management and fire exclusion practices. Because different paleoecological proxies record unique information about wildfire characteristics at different spatial and temporal scales, this research used a combination of tree-ring stand initiation, fire scar, and macroscopic sedimentary charcoal fire records to reconstruct the wildfire regime. Results revealed historical regional evidence of mixed-severity fire regimes. Multi-scale evidence of high-severity fire, including regional pulses in establishment and stand-level cohort initiation, were found, as well as an abundance of fire scar evidence, suggesting low-severity fires were also present. Results indicated that many fire events were small and localized, sometimes affecting as little as a single tree. These results suggest a mixed-severity fire regime classification for this region. Evidence for large and severe fires was broadly coherent between tree-ring and sedimentary records, but was less coherent for smaller and low severity fires. This research concludes that typical fire event detection criteria bias fire history records against mixed-severity fire. In regions experiencing complex and variable fire activity, all fire evidence should be included in regime classification. Furthermore, this research concludes that climate is a weak driver of wildfire in this region, and local landscape characteristics that mediate fuel moisture are more important. This research also demonstrates the value of macroscopic sedimentary charcoal records to fire histories in the region. While macroscopic sedimentary charcoal records are not spatially explicit and have a coarse temporal resolution, they do provide a good indication of regional fire activity prior to the start of the tree-ring fire record in this region. This is especially important in mixed-severity regimes where the record of fire is often destroyed by subsequent high-severity fires.
Date: 2016-04
Rights: Attribution 2.5 Canada

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Attribution 2.5 Canada Except where otherwise noted, this item's license is described as Attribution 2.5 Canada