Globally, peatlands have been affected by drainage and peat extraction, with adverse effects on their functioning and services. To restore peat-forming vegetation, drained bogs are being rewetted on a large scale. Although this practice results in higher groundwater levels, unfortunately it often creates deep lakes in parts where peat was extracted to greater depths than the surroundings. Revegetation of these deeper waters by peat mosses appears to be challenging due to strong abiotic feedbacks that keep these systems in an undesired bare state. In this study, we theoretically explore if a floating peat mat and an open human-made bog lake can be considered two alternative stable states using a simple model, and experimentally test in the field whether stable states are present, and whether a state shift can be accomplished using floating biodegradable structures that mimic buoyant peat. We transplanted two peat moss species into these structures (pioneer sp. Sphagnum cuspidatum and later-successional sp. S. palustre) with and without additional organic substrate. Our model suggests that these open human-made bog lakes and floating peat mats can indeed be regarded as alternative stable states. Natural recovery by spontaneous peat moss growth, i.e., a state shift from open water to floating mats, is only possible when the water table is sufficiently shallow to avoid light limitation (<0.29 m at our site). Our experiment revealed that alternative stable states are present and that the floating structures facilitated the growth of pioneer S. cuspidatum and vascular plants. Organic substrate addition particularly facilitated vascular plant growth, which correlated to higher moss height. The structures remained too wet for the late-successional species S. palustre. We conclude that open water and floating peat mats in human-made bog lakes can be considered two alternative stable states, and that temporary floating establishment structures can induce a state shift from the open water state to peat-forming vegetation state. These findings imply that for successful restoration, there is a clear water depth threshold to enable peat moss growth and there is no need for addition of large amounts of donor-peat substrate. Correct species selection for restoration is crucial for success.

中文翻译：

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克服人造沼泽池中泥炭藓的建立阈值

在全球范围内，泥炭地受到排水和泥炭开采的影响，对其功能和服务产生不利影响。为了恢复形成泥炭的植被，正在大规模重新润湿排干的沼泽。尽管这种做法会导致地下水位升高，但不幸的是，它通常会在泥炭被提取到比周围环境更深的部分形成深湖。由于强烈的非生物反馈使这些系统处于不希望的裸露状态，泥炭藓对这些更深水域的重新植被似乎具有挑战性。在这项研究中，我们从理论上探索是否可以使用简单的模型将漂浮的泥炭垫和开放的​​人造沼泽湖视为两种替代的稳定状态，并在现场进行实验测试是否存在稳定状态，以及是否可以使用模拟漂浮泥炭的漂浮可生物降解结构来实现状态转变。我们将两种泥炭藓物种移植到这些结构中（pioneer sp.Sphagnum cuspidatum和后继物种。S. palustre ) 有和没有额外的有机底物。我们的模型表明，这些开放的人造沼泽湖和漂浮的泥炭垫确实可以被视为替代稳定状态。通过自发泥炭藓生长的自然恢复，即从开放水域到漂浮垫的状态转变，只有当地下水位足够浅以避免光照限制（我们的站点 <0.29 m）时才有可能。我们的实验表明存在替代的稳定状态，并且浮动结构促进了先锋虎杖的生长和维管植物。添加有机基质特别促进维管植物生长，这与较高的苔藓高度相关。对于后继物种S. palustre 而言，这些结构仍然过于潮湿。我们得出的结论是，人造沼泽湖中的开放水域和漂浮的泥炭垫可以被认为是两种替代的稳定状态，并且临时漂浮设施结构可以诱导从开放水域状态到泥炭形成植被状态的状态转变。这些发现意味着，为了成功恢复，有一个明确的水深阈值来促进泥炭苔藓的生长，并且不需要添加大量的供体-泥炭基质。正确选择恢复物种对成功至关重要。