Limited release of previously-frozen C and increased new peat formation after thaw in permafrost peatlands
Limited release of previously-frozen C and increased new peat formation after thaw in permafrost peatlands
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DOI：
10.1016/j.soilbio.2017.12.010
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发表时间：
2018-03-01
影响因子：
9.7
通讯作者：
Hartley, Iain P.
中科院分区：
文献类型：
--
作者：
Estop-Aragones, Cristian;Cooper, Mark D. A.;Hartley, Iain P.
永久冻土储存了全球大量的碳（C），随着全球变暖促进大面积解冻，这些碳可能开始分解并以二氧化碳（CO2）和甲烷（CH 4）的形式释放到大气中。这种永冻土碳对气候的反馈目前被认为是气候模型中缺失的最重要的碳循环反馈。预测反馈的幅度需要更好地了解解冻后环境条件的差异，特别是水文条件，控制C释放到大气中的速率。在加拿大西北部的零星和不连续的永久冻土区，我们测量了相对不受干扰的生态系统中释放的C的速率和来源，并将其与经历野火（排水良好，有氧条件）和泥炭高原塌陷（积水，缺氧条件）后解冻的森林进行了比较。使用放射性碳分析，我们发现了大量的贡献，深层土壤层和/或以前冻结的来源，在我们的排水良好的网站。相比之下，没有损失的先前冻结的C作为CO2被检测到平均从崩溃的泥炭高原，无论时间，因为解冻，尽管更大的可用C的存储被曝光。此外，更大的新泥炭形成率导致这些土壤成为更强的碳汇，这种更大的吸收率似乎弥补了很大比例的CH 4排放量的增加，从崩溃的湿地。我们的结论是，在我们研究的生态系统中，土壤水分和氧气供应的变化可能比以前预测的更重要，在确定永久冻土融化对生态系统碳平衡的影响，因此，它是必不可少的监测，并准确地模拟，区域表面湿度的变化。
Permafrost stores globally significant amounts of carbon (C) which may start to decompose and be released to the atmosphere in form of carbon dioxide (CO2) and methane (CH4) as global warming promotes extensive thaw. This permafrost carbon feedback to climate is currently considered to be the most important carbon-cycle feedback missing from climate models. Predicting the magnitude of the feedback requires a better understanding of how differences in environmental conditions post-thaw, particularly hydrological conditions, control the rate at which C is released to the atmosphere. In the sporadic and discontinuous permafrost regions of north-west Canada, we measured the rates and sources of C released from relatively undisturbed ecosystems, and compared these with forests experiencing thaw following wildfire (well-drained, oxic conditions) and collapsing peat plateau sites (water-logged, anoxic conditions). Using radiocarbon analyses, we detected substantial contributions of deep soil layers and/or previously-frozen sources in our well-drained sites. In contrast, no loss of previously-frozen C as CO2 was detected on average from collapsed peat plateaus regardless of time since thaw and despite the much larger stores of available C that were exposed. Furthermore, greater rates of new peat formation resulted in these soils becoming stronger C sinks and this greater rate of uptake appeared to compensate for a large proportion of the increase in CH4 emissions from the collapse wetlands. We conclude that in the ecosystems we studied, changes in soil moisture and oxygen availability may be even more important than previously predicted in determining the effect of permafrost thaw on ecosystem C balance and, thus, it is essential to monitor, and simulate accurately, regional changes in surface wetness.