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首页> 外文期刊>Global change biology >The effect of fire and permafrost interactions on soil carbon accumulation in an upland black spruce ecosystem of interior Alaska: implications for post-thaw carbon loss
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The effect of fire and permafrost interactions on soil carbon accumulation in an upland black spruce ecosystem of interior Alaska: implications for post-thaw carbon loss

机译：火和多年冻土相互作用对阿拉斯加内陆黑云杉生态系统土壤碳积累的影响：对融化后碳损失的影响

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摘要

High-latitude regions store large amounts of organic carbon (OC) in active-layer soils and permafrost, accounting for nearly half of the global belowground OC pool. In the boreal region, recent warming has promoted changes in the fire regime, which may exacerbate rates of permafrost thaw and alter soil OC dynamics in both organic and mineral soil. We examined how interactions between fire and permafrost govern rates of soil OC accumulation in organic horizons, mineral soil of the active layer, and near-surface permafrost in a black spruce ecosystem of interior Alaska. To estimate OC accumulation rates, we used chronosequence, radiocarbon, and modeling approaches. We also developed a simple model to track long-term changes in soil OC stocks over past fire cycles and to evaluate the response of OC stocks to future changes in the fire regime. Our chronosequence and radiocarbon data indicate that OC turnover varies with soil depth, with fastest turnover occurring in shallow organic horizons (similar to 60 years) and slowest turnover in near-surface permafrost (> 3000 years). Modeling analysis indicates that OC accumulation in organic horizons was strongly governed by carbon losses via combustion and burial of charred remains in deep organic horizons. OC accumulation in mineral soil was influenced by active layer depth, which determined the proportion of mineral OC in a thawed or frozen state and thus, determined loss rates via decomposition. Our model results suggest that future changes in fire regime will result in substantial reductions in OC stocks, largely from the deep organic horizon. Additional OC losses will result from fire-induced thawing of near-surface permafrost. From these findings, we conclude that the vulnerability of deep OC stocks to future warming is closely linked to the sensitivity of permafrost to wildfire disturbance.
机译：高纬度地区在活动层土壤和多年冻土中存储大量有机碳（OC），约占全球地下OC池的近一半。在北方地区，最近的变暖促进了火势的变化，这可能会加剧永久冻土的融化速率，并改变有机土壤和矿物土壤中土壤OC的动态。我们研究了火与多年冻土之间的相互作用如何控制阿拉斯加内部黑色云杉生态系统中有机层，活性层矿物土壤和近地表多年冻土中土壤OC积累的速率。为了估算OC累积速率，我们使用了时间序列，放射性碳和建模方法。我们还开发了一个简单的模型来跟踪过去火灾周期中土壤OC储量的长期变化，并评估OC储量对火灾状况未来变化的响应。我们的时间序列和放射性碳数据表明，OC转换量随土壤深度而变化，在浅有机层（大约60年）中转换最快，而在近地表多年冻土中（> 3000年）转换最慢。建模分析表明，有机层中的OC积累受燃烧和埋藏在深有机层中焦炭残渣的碳损失的强烈控制。矿质土壤中的OC积累受活性层深度的影响，活性层深度决定了融化或冷冻状态下矿质OC的比例，因此确定了分解引起的损失率。我们的模型结果表明，未来火灾情况的变化将导致有机碳库存的大量减少，而这主要是来自深层次的有机观察。火灾造成的近地表永久冻土融化将导致额外的OC损失。根据这些发现，我们得出结论，深层OC储量对未来变暖的脆弱性与多年冻土对野火干扰的敏感性密切相关。

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