Rocky Mountain subalpine forests now burning more than any time in recent millennia
Rocky Mountain subalpine forests now burning more than any time in recent millennia
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DOI：
10.1073/pnas.2103135118
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发表时间：
2021-06-22
影响因子：
11.1
通讯作者：
Wolf, Kyra D.
中科院分区：
文献类型：
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作者：
Higuera, Philip E.;Shuman, Bryan N.;Wolf, Kyra D.
2020年的火灾季节打破了美国西部长达数十年的火灾活动增加的趋势，自1984年以来，落基山脉中部的火灾总面积几乎翻了一番。了解这种极端火灾季节的原因和影响，特别是在历史上很少发生火灾的亚高山森林中，需要一个长期的视角，而这是观测记录所不能提供的。我们将21世纪亚高山森林的火灾活动放在过去2,000年的气候和火灾历史的背景下，使用20个古火灾记录的独特网络。由于2020年的大规模燃烧，21世纪的火灾轮换期现在是117年，反映了过去2,000年平均燃烧率的近两倍。更引人注目的是，现在的燃烧率比过去两千年重建的最大速率高出22%，在中世纪早期气候异常（MCA）（公元770至870年），当时北方半球的温度比20世纪的平均温度高出0.3摄氏度。因此，2020年的火灾季节表明，随着气候变暖，极端事件正在划分新出现的火灾制度。随着21世纪世纪的气温超过了MCA，落基山脉亚高山森林的火灾活动超过了数千年来塑造这些生态系统的变化范围。
The 2020 fire season punctuated a decades-long trend of increased fire activity across the western United States, nearly doubling the total area burned in the central Rocky Mountains since 1984. Understanding the causes and implications of such extreme fire seasons, particularly in subalpine forests that have historically burned infrequently, requires a long-term perspective not afforded by observational records. We place 21st century fire activity in subalpine forests in the context of climate and fire history spanning the past 2,000 y using a unique network of 20 paleofire records. Largely because of extensive burning in 2020, the 21st century fire rotation period is now 117 y, reflecting nearly double the average rate of burning over the past 2,000 y. More strikingly, contemporary rates of burning are now 22% higher than the maximum rate reconstructed over the past two millennia, during the early Medieval Climate Anomaly (MCA) (770 to 870 Common Era), when Northern Hemisphere temperatures were similar to 0.3 degrees C above the 20th century average. The 2020 fire season thus exemplifies how extreme events are demarcating newly emerging fire regimes as climate warms. With 21st century temperatures now surpassing those during the MCA, fire activity in Rocky Mountain subalpine forests is exceeding the range of variability that shaped these ecosystems for millennia.