Climate change is transforming forest structure and function by altering the timing, frequency, intensity, and spatial extent of episodic disturbances. Wildland fire regimes in western U.S. coniferous forests are now characterized by longer fire seasons and greater frequency, with further changes expected. Identifying the impacts of altered fire regimes on forest resources may enable land managers to plan mitigation strategies or prepare for novel or altered communities. We created a stochastic, density‐dependent, matrix projection model for a whitebark pine (Pinus albicaulis) metapopulation to estimate the impacts of increasing fire frequency on metapopulation persistence. Whitebark pine is a widely distributed foundation species of management concern found in upper subalpine and tree line forests of the Northern Rocky Mountains. We parameterized the model using empirically based demographic data from the Greater Yellowstone Ecosystem (GYE) and validated the model by comparing observed whitebark pine densities to those projected by the model when parameterized with historical demographic rates and fire frequencies. We reparameterized the model with current demographic rates including mortality from insect outbreaks and exotic disease. We compared odds of functional extirpation among six scenarios comprising three altered fire frequencies (fires suppressed, historical fire return interval of 268 yr, and decreasing fire return intervals from current to 97 yr) and two seed dispersal probabilities. Historical parameterization with high dispersal probability projected median whitebark pine densities (40.95 trees/ha, first and third quartiles: 21.89, 67.25), which were similar to empirically estimated densities (40.62 trees/ha, first and third quartiles: 12.04, 114.15). Odds of functional extirpation with increasing fire frequency were 8.26 and 139.91 times higher than historical fire frequency and fire suppression, respectively. In decreasing fire return interval scenarios, odds of functional extirpation were 1.76 times higher in low than high dispersal probability scenarios. These findings suggest that fire suppression may be required to maintain whitebark pine metapopulations in the GYE and that maintaining stand networks connected by high rates of seed dispersal could increase metapopulation resiliency.

中文翻译：

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气候变化的火情可能增加管理关注的亚高山针叶树种的灭绝风险

气候变化通过改变偶发性干扰的时间，频率，强度和空间范围，正在改变森林的结构和功能。现在，美国西部针叶林的野地火灾状况具有更长的火灾季节和更高的频率，并有望进一步改变。查明火灾制度的改变对森林资源的影响，可使土地管理者制定缓解策略或为新的或改变的社区做准备。我们为白皮松（Pinus albicaulis）创建了一个随机的，依赖于密度的矩阵投影模型）以估计火灾频率增加对持久性种群的影响。白皮松是在北落基山脉的上亚高山和林木森林中发现的一种引起管理广泛关注的基础物种。我们使用来自大黄石生态系统（GYE）的基于经验的人口统计学数据对模型进行参数化，并通过将观察到的白皮松密度与模型预测的历史密度和火灾频率进行参数化比较，从而验证了模型。我们使用当前人口统计率（包括昆虫爆发和外来疾病导致的死亡率）对模型进行了重新参数化。我们比较了六种情况下功能消亡的几率，其中包括三种改变的起火频率（抑制起火，历史回火间隔268年，并将回火间隔从当前降低到97年）和两个种子扩散概率。具有高分散概率的历史参数化预计白皮松中位密度（40.95棵树/公顷，第一和第三四分位数：21.89，67.25），与经验估计的密度（40.62棵树/公顷，第一和第三四分位数：12.04，114.15）相似。随着火灾频率的增加，功能性熄灭的几率分别比历史火灾频率和灭火高出8.26倍和139.91倍。在降低回火间隔的情况下，低发散的可能性比高散发概率下的发泄的可能性高1.76倍。