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

虽然火灾是推动植被动态和本地物种进化的一个中心过程，但加拿大西部山区森林火灾制度的时空变化仍然知之甚少。火灾制度受到气候、燃料和人类的强烈影响。气候被认为是火灾制度的“自上而下”的驱动因素，在广泛的空间尺度和从几天到几年甚至几十年的时间尺度上影响有利于火灾的条件。燃料的可获得性和可燃性是对火的“自下而上”的控制，并受到当地地形的强烈影响，如坡度和海拔高度。此外，在许多干燥森林类型中，由于土地利用变化和灭火导致的火灾排除，燃料已经积累。自上而下和自下而上控制火灾的相对重要性因地理和森林类型而异，但我们需要进一步了解具体的机制、相互作用和人类影响。我的长期科学目标是建立预测模型，量化山地森林不同火灾状况的特征(频率、严重程度、范围)，并区分气候、燃料和人类土地利用对这些状况的相对重要性。短期内，我和我的研究生们将使用树生态(树轮)重建来研究落基山沟南部山地(1100-1600masl)和亚高山(1600masl)森林火灾历史在多个空间和时间尺度上的变化。我们实地研究的目标是：(1)区分自下而上燃料和自上而下气候控制对历史火灾频率/严重程度的相互影响；(2)确定人类土地利用(LU)对这些控制的影响。对火势机制和控制的更深入的了解将使我们能够预测未来在全球气候变化影响下的火势，识别因过去的土地使用而显著改变并需要生态恢复的景观部分，以及建立库特奈国家公园生态恢复和燃料缓解的优先事项和目标。

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.