Fens and bogs are distinct in terms of their biogeochemistry, water table behavior, and net peat-accumulation regimes. While most peatlands start developing as fens, a large fraction of them eventually shift to bogs in a step-like ecosystem shift. This transition has traditionally been assumed to be primarily controlled by the ecosystem itself (autogenic control). Here we use 90 peat profiles from southernmost South America (SSA) as a case study that illustrates a synchronous, regional-scale shift from fen to bog around 4200 years ago. In light of these results, we propose and discuss conceptual models that link environmental change (allogenic control) as a trigger to the fen-bog transition (FBT). In addition, our stratigraphic analyses show that Sphagnum deposits are associated with greater peat masses, larger soil-carbon stocks, and higher rates of peat-carbon accumulation than their non-Sphagnum counterparts, with Sphagnum bogs being characterized by soil-carbon densities over twice that of non-Sphagnum peatlands (medians = 141 vs. 56 kgC/m2). Since fens and bogs also behave differently in terms of their carbon exchanges with the atmosphere, a better appraisal of the processes involved in the FBT could help elucidate the role of this critical ecosystem shift in the past and future global carbon cycle.

中文翻译：

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巴塔哥尼亚南部的沼泽突然转变：时间、原因和对碳封存的影响

沼泽和沼泽在生物地球化学、地下水位行为和泥炭净积累机制方面是不同的。虽然大多数泥炭地开始发展为沼泽，但其中很大一部分最终会以阶梯式的生态系统转变为沼泽。传统上认为这种转变主要由生态系统本身控制（自生控制）。在这里，我们使用来自南美洲最南端 (SSA) 的 90 个泥炭剖面作为案例研究，说明了大约 4200 年前从沼泽到沼泽的同步区域尺度转变。根据这些结果，我们提出并讨论了将环境变化（同种异体控制）作为沼泽过渡（FBT）的触发器的概念模型。此外，我们的地层分析表明，泥炭藓沉积物与更大的泥炭块、更大的土壤碳储量、泥炭碳积累率高于非泥炭沼泽，泥炭沼泽的土壤碳密度是非泥炭沼泽地的两倍（中位数 = 141 vs. 56 kgC/m2）。由于沼泽和沼泽在与大气的碳交换方面也有不同的表现，更好地评估 FBT 所涉及的过程可以帮助阐明这一关键生态系统转变在过去和未来全球碳循环中的作用。