Arctic and boreal paleofire records reveal drivers of fire activity and departures from Holocene variability
Arctic and boreal paleofire records reveal drivers of fire activity and departures from Holocene variability
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DOI：
10.1002/ecy.3096
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发表时间：
2020-06-09
期刊：
影响因子：
4.8
通讯作者：
Hu, Feng Sheng
中科院分区：
文献类型：
--
作者：
Hoecker, Tyler J.;Higuera, Philip E.;Hu, Feng Sheng
北方森林和苔原生物群落是地球系统的关键组成部分，因为大量碳储存的调动和能量平衡的变化可以作为对持续气候变化的积极反馈。在阿拉斯加，野火是生态系统结构和功能的主要驱动力，也是高纬度生态系统与全球气候耦合的关键机制。古生态记录显示，火灾制度的气候和植被变化的敏感性超过百年，千年的时间尺度，突出增加燃烧同时变暖或景观可燃性升高。为了量化火灾制度的变化的时空模式，我们合成了27个已发表的沉积物木炭记录从阿拉斯加的四个生态区，并比较模式的古气候和古植被记录。生物量燃烧和火灾频率显着增加，在北方森林生态区与扩展的黑云杉，约。距今6000 - 4000年（yr BP）。生物量燃烧也增加了温暖时期，特别是在育空地区平原生态区从约。距今1,000至500年。生物质燃烧的增加与恒定的火灾返回间隔同时发生，表明平均火灾严重程度的增加（即，在温暖时期，每次火灾燃烧更多的生物质）。结果还表明，上个世纪阿拉斯加大部分地区生物质燃烧的增加超过了全新世最大值，为持续变化提供了重要背景。我们的分析记录了火灾活动对大规模环境变化的敏感性，包括气候变暖和植被生物群规模的变化。缺乏广泛的，长期的火灾同步表明区域异质性有限的同时火灾制度的变化在我们的研究领域在全新世。这一发现意味着北方森林对广泛的火灾活动具有广泛的弹性，但并不排除对21世纪变化的新反应。如果预测的火灾活动在21世纪的增加成为现实，那么在过去8,000年或更长时间的背景下，这将是前所未有的。
Boreal forest and tundra biomes are key components of the Earth system because the mobilization of large carbon stocks and changes in energy balance could act as positive feedbacks to ongoing climate change. In Alaska, wildfire is a primary driver of ecosystem structure and function, and a key mechanism coupling high-latitude ecosystems to global climate. Paleoecological records reveal sensitivity of fire regimes to climatic and vegetation change over centennial-millennial time scales, highlighting increased burning concurrent with warming or elevated landscape flammability. To quantify spatiotemporal patterns in fire-regime variability, we synthesized 27 published sediment-charcoal records from four Alaskan ecoregions, and compared patterns to paleoclimate and paleovegetation records. Biomass burning and fire frequency increased significantly in boreal forest ecoregions with the expansion of black spruce, ca. 6,000-4,000 years before present (yr BP). Biomass burning also increased during warm periods, particularly in the Yukon Flats ecoregion from ca. 1,000 to 500 yr BP. Increases in biomass burning concurrent with constant fire return intervals suggest increases in average fire severity (i.e., more biomass burning per fire) during warm periods. Results also indicate increases in biomass burning over the last century across much of Alaska that exceed Holocene maxima, providing important context for ongoing change. Our analysis documents the sensitivity of fire activity to broad-scale environmental change, including climate warming and biome-scale shifts in vegetation. The lack of widespread, prolonged fire synchrony suggests regional heterogeneity limited simultaneous fire-regime change across our study areas during the Holocene. This finding implies broad-scale resilience of the boreal forest to extensive fire activity, but does not preclude novel responses to 21st-century changes. If projected increases in fire activity over the 21st century are realized, they would be unprecedented in the context of the last 8,000 yr or more.