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

尽管火灾是驱动植被动态和本地物种进化的核心过程，但人们对不列颠哥伦比亚省山林火灾制度的时空变化知之甚少。火灾制度受气候、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”驱动因素，在广泛的空间尺度和从几天到几年到几十年的时间尺度范围内影响有利于火灾的条件。燃料的可用性和可燃性是“自下而上”的火灾控制，并受到当地地形（如坡度和海拔）的强烈影响。此外，在许多干燥的森林类型中，由于土地利用的变化和随后的灭火导致的禁火，燃料已经积累起来。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机制、相互作用和人类影响。我的长期科学目标是量化山林中不同火灾状态的特征（频率、严重程度、程度），并区分气候、燃料和人类土地利用对这些状态的相对重要性。在短期内，我和我的研究生将利用树木生态学（树木年轮）重建来研究落基山海沟（SRMT）南部亚山地（<1100 masl）、山地（1100-1600masl）和亚高山（1000 -1600masl）森林的火灾历史在多个时空尺度上的变化。我们实地研究的目标是：(1)区分自下而上的燃料与自上而下的气候控制对历史火灾频率/严重程度的相互影响；(2)确定人类土地利用对这些控制的影响。对火灾机制和控制的更好理解将使我们能够在全球气候变化的影响下预测未来的火灾情况，确定受过去土地利用显著改变的景观部分，并在荒地-城市界面、公园和保护区建立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 the mountain forests of BC is 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 are "bottom-up" controls of fire and are 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 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 submontane (<1100 masl), 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 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 establish priorities and targets for ecological restoration and fuels mitigation in the wildland-urban interface, parks, and protected areas.