Soil data and age models used to investigate the effects of permafrost thaw on carbon storage, Interior Alaska

We quantified permafrost plateau carbon (C) and post-thaw C stocks across a peatland permafrost thaw chronosequence in Interior Alaska to evaluate whether C losses occurred with thaw . Peat core macrofossil reconstructions revealed three stratigraphic layers of peat: (1) a base layer of fen/marsh peat, (2) forested permafrost plateau peat and, (3) where permafrost thaw has occurred, collapse-scar bog peat. Radiocarbon dating revealed that peat initiated at all sites within the last 2,500 years, and dating transitions between stratigraphic layers allowed us to determine that permafrost aggraded during the Little Ice Age and degraded within the last several decades. We found the timing of permafrost thaw within each feature was not related to thaw bog size, as hypothesized. The rate of expansion may be more influenced by local factors, such as ground ice content and subsurface water inputs. We found C losses in the century following thaw were lower than losses previously described in other Alaskan peatland chronosequences. We hypothesize that the difference stems from the process by which permafrost aggraded, with sites that formed permafrost epigenetically, i.e. significantly later than the majority of peat accumulation, experiencing less C loss with thaw than sites that formed syngenetically, i.e. simultaneously with peat accumulation. We suggest that N concentration and C:N ratios can provide a first order estimate of how much peat has been processed prior to permafrost aggradation, helping to predict the magnitude of C loss with thaw.

本研究针对阿拉斯加内陆一处发育有多年冻土解冻年代序列的泥炭地，量化了多年冻土台地碳（C）储量与解冻后碳储量，以评估冻土融化是否会引发碳损失。通过泥炭岩芯大化石重建分析，本研究识别出三类泥炭地层：（1）底层为富营养沼泽（fen）/草本沼泽（marsh）泥炭；（2）中层为森林覆盖型多年冻土台地泥炭；（3）经历多年冻土融化区域的塌陷坑沼泽泥炭。放射性碳定年结果显示，所有样地的泥炭均形成于过去2500年内；通过地层界面的定年分析，我们确定该区域多年冻土于小冰期发育，并在近数十年内发生退化。研究发现，各区域多年冻土融化的时间与解冻沼泽规模并无关联，这与此前的研究假设一致。沼泽扩张速率则更易受局地因素影响，例如地下冰含量与地下水补给量。我们发现，冻土融化后百年内的碳损失量低于此前阿拉斯加其他泥炭地年代序列样地报道的碳损失水平。我们推测，该差异源于多年冻土的发育过程：后生型多年冻土（即形成时间显著晚于多数泥炭堆积过程的冻土）在融化后的碳损失量，低于同生型多年冻土（即与泥炭堆积同步形成的冻土）。本研究提出，氮浓度与碳氮比可用于一级估算多年冻土发育前泥炭的改造程度，从而助力预测冻土融化引发的碳损失规模。