The influence of vegetation and soil characteristics on active-layer thickness of permafrost soils in boreal forest.
The influence of vegetation and soil characteristics on active-layer thickness of permafrost soils in boreal forest.
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DOI：
10.1111/gcb.13248
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发表时间：
2016-09
影响因子：
11.6
通讯作者：
Phoenix GK
中科院分区：
文献类型：
--
作者：
Fisher JP;Estop-Aragonés C;Thierry A;Charman DJ;Wolfe SA;Hartley IP;Murton JB;Williams M;Phoenix GK
随着活动层的加深，融化的永久冻土中的碳释放可能会显著加剧全球变暖，使更多的碳暴露在腐烂中。植物群落和土壤特性通过影响每年夏季的最大解冻深度（活性层厚度; ALT）提供了对此的主要控制，但目前缺乏对植物和土壤特性的相对重要性及其在确定ALT中的相互作用的定量理解。为了解决这一问题，我们进行了广泛的调查，多个植被和土壤特征和ALT跨多个地块在四个实地站点内的北方森林在不连续的永久冻土带（西北地区，加拿大）。我们的研究地点包括成熟的黑云杉、燃烧过的黑云杉和纸皮桦，使我们能够确定在这些关键植被和干扰梯度中最重要和最广泛适用的植被和土壤驱动因素，并深入了解特定地点的差异。在整个网站，最重要的植被特征限制解冻（浅ALT）的树叶面积指数（LAI），苔藓层厚度和林下叶面积指数在该顺序。较厚的土壤有机层也降低了ALT，虽然影响小于苔藓厚度。表层水分（0-6厘米）促进了ALT的增加，而深层土壤水分（11-16厘米）则起到了改变植被影响的作用，特别是增加了林下或树冠遮荫在减少解冻方面的重要性。水分的这些直接和间接影响表明，未来降水和蒸散的变化可能对ALT有很大的影响。我们的工作还表明，森林火灾导致更大的ALT，同时减少多种生态系统特征，否则保护永冻土。鉴于植被和土壤特征对ALT有如此明显和巨大的影响，我们的数据提供了一个关键的基准，用于评估用于预测未来气候变暖对永久冻土退化的影响以及随后对气候的反馈的过程模型。
Carbon release from thawing permafrost soils could significantly exacerbate global warming as the active‐layer deepens, exposing more carbon to decay. Plant community and soil properties provide a major control on this by influencing the maximum depth of thaw each summer (active‐layer thickness; ALT), but a quantitative understanding of the relative importance of plant and soil characteristics, and their interactions in determine ALTs, is currently lacking. To address this, we undertook an extensive survey of multiple vegetation and edaphic characteristics and ALTs across multiple plots in four field sites within boreal forest in the discontinuous permafrost zone (NWT, Canada). Our sites included mature black spruce, burned black spruce and paper birch, allowing us to determine vegetation and edaphic drivers that emerge as the most important and broadly applicable across these key vegetation and disturbance gradients, as well as providing insight into site‐specific differences. Across sites, the most important vegetation characteristics limiting thaw (shallower ALTs) were tree leaf area index (LAI), moss layer thickness and understory LAI in that order. Thicker soil organic layers also reduced ALTs, though were less influential than moss thickness. Surface moisture (0–6 cm) promoted increased ALTs, whereas deeper soil moisture (11–16 cm) acted to modify the impact of the vegetation, in particular increasing the importance of understory or tree canopy shading in reducing thaw. These direct and indirect effects of moisture indicate that future changes in precipitation and evapotranspiration may have large influences on ALTs. Our work also suggests that forest fires cause greater ALTs by simultaneously decreasing multiple ecosystem characteristics which otherwise protect permafrost. Given that vegetation and edaphic characteristics have such clear and large influences on ALTs, our data provide a key benchmark against which to evaluate process models used to predict future impacts of climate warming on permafrost degradation and subsequent feedback to climate.