Fire is an integral natural disturbance in the moist temperate forests of the Pacific Northwest of the United States, but future changes remain uncertain. Fire regimes in this climatically and biophysically diverse region are complex, but typically climate limited. One challenge for interpreting potential changes is conveying projection uncertainty. Using projections of Energy Release Component (ERC) derived from 12 global climate models (GCM) that vary in performance relative to the region's contemporary climate, we simulated thousands of plausible fire seasons with the stochastic spatial fire spread model FSim for mid-21st century (2035–2064) under RCP8.5 emissions scenario for five northwestern pyromes. The magnitude of projected changes to burn probability, fire size, and number of fires varied among pyromes and GCMs. We projected the largest increases in burn probability and fire size in the cooler and wetter northern parts of the region (North Cascades, Olympics & Puget Lowlands) and Oregon West Cascades, with more moderate changes projected for the Washington West Cascades and Oregon Coast Range. We provide new insights into changing fire regimes characterized by the possibility of shifts toward more frequent and large fires (especially >40,000 ha), as well as shifts in seasonality, including more fires burning at the beginning of fall when extreme synoptic weather events have the potential to increase fire spread. Our work highlights the potential geographic variability in climate change effects in some of the most productive moist temperate forests of the world and points to a rapid acceleration of fire in the coming decades.

中文翻译：

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模拟美国西北太平洋潮湿森林野火状况的未来变化

火灾是美国太平洋西北部潮湿温带森林中不可或缺的自然干扰，但未来的变化仍然不确定。这个气候和生物物理多样化的地区的火灾状况很复杂，但通常受到气候的限制。解释潜在变化的一项挑战是传达预测的不确定性。利用根据 12 个全球气候模型 (GCM) 得出的能量释放分量 (ERC) 预测（这些模型的性能相对于该地区的当代气候而言各不相同），我们使用 21 世纪中叶的随机空间火灾蔓延模型 FSim 模拟了数千个可能的火灾季节（ 2035–2064）在 RCP8.5 排放情景下，西北五个火炉的排放情景。燃烧概率、火灾规模和火灾数量的预计变化幅度在高温和全球气候变暖中有所不同。我们预计该地区较凉爽和湿润的北部地区（北喀斯喀特地区、奥林匹克和普吉特低地）和俄勒冈州西喀斯喀特地区的燃烧概率和火灾规模增幅最大，预计华盛顿西喀斯喀特地区和俄勒冈海岸山脉的变化较为温和。我们对不断变化的火灾状况提供了新的见解，这些火灾状况的特点是可能会转向更频繁和大规模的火灾（尤其是> 40,000公顷），以及季节性的变化，包括在秋季初发生更多火灾，此时极端天气事件会发生。增加火势蔓延的可能性。我们的工作强调了气候变化影响世界上一些生产力最高的湿润温带森林的潜在地理变异性，并指出未来几十年火灾将迅速加速。