Increasing wildfires threaten historic carbon sink of boreal forest soils
Increasing wildfires threaten historic carbon sink of boreal forest soils
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DOI：
10.1038/s41586-019-1474-y
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发表时间：
2019-08-22
期刊：
影响因子：
64.8
通讯作者：
Mack, Michelle C.
中科院分区：
文献类型：
--
作者：
Walker, Xanthe J.;Baltzer, Jennifer L.;Mack, Michelle C.
北方森林火灾主要通过燃烧土壤有机物向大气中排放大量碳（1-3）。在每次火灾期间，燃烧层下面的一部分土壤可以逃脱燃烧，导致森林中的碳在多次火灾事件中净积累。气候变暖和干燥导致更严重和更频繁的森林火灾（5-7），这可能会使北方生态系统的碳平衡从净积累转变为净损失（1），导致积极的气候反馈（8）。如果在之前的火灾中逃脱燃烧的有机土壤碳（称为“遗留碳”）燃烧，就会发生这种反馈。在这里，我们使用土壤放射性碳测年来定量评估加拿大西北地区2014年野火中的遗留碳损失（2）。我们没有发现任何证据表明，在比西北部北方森林历史火灾返回间隔更古老的森林中，遗留的碳燃烧。在火灾发生时处于干燥景观且年龄不到60岁的森林中，在上一次火灾周期中逃脱燃烧的遗留碳被燃烧。我们估计，34万公顷的幼林（
Boreal forest fires emit large amounts of carbon into the atmosphere primarily through the combustion of soil organic matter(1-3). During each fire, a portion of this soil beneath the burned layer can escape combustion, leading to a net accumulation of carbon in forests over multiple fire events(4). Climate warming and drying has led to more severe and frequent forest fires(5-7), which threaten to shift the carbon balance of the boreal ecosystem from net accumulation to net loss(1), resulting in a positive climate feedback(8). This feedback will occur if organic-soil carbon that escaped burning in previous fires, termed 'legacy carbon', combusts. Here we use soil radiocarbon dating to quantitatively assess legacy carbon loss in the 2014 wildfires in the Northwest Territories of Canada(2). We found no evidence for the combustion of legacy carbon in forests that were older than the historic fire-return interval of northwestern boreal forests(9). In forests that were in dry landscapes and less than 60 years old at the time of the fire, legacy carbon that had escaped burning in the previous fire cycle was combusted. We estimate that 0.34 million hectares of young forests (