Fire regimes in mountain landscapes and global environmental change: top-down versus bottom-up controls

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Although fire is a central process driving vegetation dynamics and the evolution of native species, the spatial and temporal variation in fire regimes of mountain forests in western Canada remains poorly understood. Fire regimes are strongly influenced by climate, fuels and humans. Climate is considered a "top-down" driver of fire regimes, influencing conditions conducive to fire at broad spatial scales and at a range of time scales from days to years to decades. Fuel availability and combustibility is a "bottom-up" control of fire and is strongly influenced by local topography such as slope aspect and elevation. Moreover, in many dry forest types, fuels have accumulated due to fire exclusion resulting from land use changes followed by fire suppression. The relative importance of top-down and bottom-up controls on fire varies geographically and by forest type, but we need further understanding of specific mechanisms, interactions and human impacts. My long-term scientific objective is to build predictive models that quantify the characteristics (frequency, severity, extent) of different fire regimes in mountain forests and distinguishes the relative importance of climate, fuels and human land use on those regimes. In the short-term, my graduate students and I will use dendroecological (tree-ring) reconstructions to investigate variation in fire history at multiple spatial and temporal scales in montane (1100-1600masl) and subalpine (>1600 masl) forests of the southern Rocky Mountain Trench (SRMT). The objectives of our field-based research are: (1) differentiate the interacting impacts of bottom-up fuels versus top-down climate controls on historic fire frequency/severity and (2) determine the impacts of human land use (LU) on these controls. Improved understanding of the mechanisms and controls of fire regimes will allow us to predict of future fire regimes under the influence of global climate change, identify segments of the landscape significantly altered by past land use and requiring ecological restoration, and establishment of priorities and targets for ecological restoration and fuels mitigation in Kootenay National Park.