Integrated Remote Sensing Studio, Faculty of Forestry, University of British Columbia, 2424 Main Mall, Vancouver, BC, Canada, V6T 1Z4.
Canadian Forest Service (Pacific Forestry Centre), Natural Resources Canada, 506 Burnside Road, Saanich, BC, Canada, V8Z 1M5.
Glob Chang Biol. 2017 Mar;23(3):1036-1047. doi: 10.1111/gcb.13456. Epub 2016 Sep 3.
Fire regimes are changing throughout the North American boreal forest in complex ways. Fire is also a major factor governing access to high-quality forage such as terricholous lichens for barren-ground caribou (Rangifer tarandus groenlandicus). Additionally, fire alters forest structure which can affect barren-ground caribou's ability to navigate in a landscape. Here, we characterize how the size and severity of fires are changing across five barren-ground caribou herd ranges in the Northwest Territories and Nunavut, Canada. Additionally, we demonstrate how time since fire, fire severity, and season result in complex changes in caribou behavioural metrics estimated using telemetry data. Fire disturbances were identified using novel gap-free Landsat surface reflectance composites from 1985 to 2011 across all herd ranges. Burn severity was estimated using the differenced normalized burn ratio. Annual area burned and burn severity were assessed through time for each herd and related to two behavioural metrics: velocity and relative turning angle. Neither annual area burned nor burn severity displayed any temporal trend within the study period. However, certain herds, such as the Ahiak/Beverly, have more exposure to fire than other herds (i.e. Cape Bathurst had a maximum forested area burned of less than 4 km ). Time since fire and burn severity both significantly affected velocity and relative turning angles. During fall, winter, and spring, fire virtually eliminated foraging-focused behaviour for all 26 years of analysis while more severe fires resulted in a marked increase in movement-focused behaviour compared to unburnt patches. Between seasons, caribou used burned areas as early as 1-year postfire, demonstrating complex, nonlinear reactions to time since fire, fire severity, and season. In all cases, increases in movement-focused behaviour were detected postfire. We conclude that changes in caribou behaviour immediately postfire are primarily driven by changes in forest structure rather than changes in terricholous lichen availability.
北美北方森林的火行为正在以复杂的方式发生变化。火也是控制贫瘠地驯鹿（Rangifer tarandus groenlandicus）等高质草料（如地衣）获取的主要因素。此外，火会改变森林结构，从而影响驯鹿在景观中的导航能力。在这里，我们描述了加拿大西北地区和努纳武特地区五个贫瘠地驯鹿牧群范围内火灾的大小和严重程度是如何变化的。此外，我们还展示了火干扰如何利用遥测数据来估计驯鹿行为指标，这些行为指标随着时间、火严重程度和季节的变化而发生复杂变化。使用 1985 年至 2011 年期间所有牧群范围内的新型无间隙 Landsat 地表反射率合成物来识别火干扰。使用差分归一化燃烧比估算燃烧严重程度。对每个牧群的年度燃烧面积和燃烧严重程度进行了随时间的评估，并与两个行为指标（速度和相对转向角度）相关联。在研究期间，无论是年度燃烧面积还是燃烧严重程度都没有表现出任何时间趋势。然而，某些牧群，如 Ahiak/Beverly，比其他牧群更容易受到火的影响（例如，Cape Bathurst 被烧毁的森林面积最大不到 4 公里）。火干扰后的时间和燃烧严重程度都显著影响了速度和相对转向角度。在秋季、冬季和春季，所有 26 年的分析中，火几乎消除了所有与觅食相关的行为，而与未燃烧斑块相比，更严重的火灾导致与移动相关的行为明显增加。在季节之间，驯鹿早在火灾发生后 1 年就开始使用火烧区，这表明它们对火干扰后的时间、火严重程度和季节表现出复杂的非线性反应。在所有情况下，都检测到了与移动相关的行为增加。我们的结论是，火后驯鹿行为的变化主要是由森林结构的变化而不是地衣可用性的变化驱动的。
