Laboratory for Ecology of Natural and Anthropised Hydrosystems (UMR 5023 CNRS), Université Lyon 1, Villeurbanne Cedex, France.
Paris Sciences & Lettres University (PSL), Ecole Pratique des Hautes Etudes (EPHE), Paris, France.
Glob Chang Biol. 2018 Jun;24(6):2476-2487. doi: 10.1111/gcb.14067. Epub 2018 Feb 21.
Up to now, the most widely accepted idea of the periglacial environment is that of treeless ecosystems such as the arctic or the alpine tundra, also called the tabula rasa paradigm. However, several palaeoecological studies have recently challenged this idea, that is, treeless environments in periglacial areas where all organisms would have been exterminated near the glacier formed during the Last Glacial Maximum, notably in the Scandinavian mountains. In the Alps, the issue of glacial refugia of trees remains unanswered. Advances in glacier reconstructions show that ice domes did not cover all upper massifs, but glaciers filled valleys. Here, we used fossils of plant and malacofauna from a travertine formation located in a high mountain region to demonstrate that trees (Pinus, Betula) grew with grasses during the Lateglacial-Holocene transition, while the glacier fronts were 200-300 m lower. The geothermal travertine started to accumulate more than 14,500 years ago, but became progressively more meteogene about 11,500 years ago due to a change in groundwater circulation. With trees, land snails (gastropods) associated to woody or open habitats and aquatic mollusc were also present at the onset of the current interglacial, namely the Holocene. The geothermal spring, due to warm water and soil, probably favoured woody glacial ecosystems. This new finding of early tree growth, combined with other scattered proofs of the tree presence before 11,000 years ago in the western Alps, changes our view of the tree distribution in periglacial environments, supporting the notion of tree refugia on nunataks in an ocean of glaciers. Therefore, the tabula rasa paradigm must be revisited because it has important consequences on the global changes, including postglacial plant migrations and biogeochemical cycles.
到目前为止，最被广泛接受的冰缘环境概念是无树生态系统，如北极或高山冻原，也称为白板范式。然而，最近的几项古生态学研究挑战了这一观点，即在末次冰期最大值形成的冰川附近，冰缘地区的无树环境中，所有生物都将被消灭，特别是在斯堪的纳维亚山脉。在阿尔卑斯山，关于树木的冰川避难所的问题仍未得到解答。冰川重建的进展表明，冰帽并没有覆盖所有的高山，而是冰川填充了山谷。在这里，我们利用位于高山地区的一个钙华地层中的植物和软体动物化石，证明了在末次冰期-全新世过渡期间，松树（Pinus、Betula）与草一起生长，而冰川前缘低 200-300 米。地热钙华开始于 14500 多年前，但由于地下水循环的变化，大约在 11500 年前，它逐渐变得更多地受到地下水的影响。随着树木的出现，与木质或开阔栖息地相关的陆生蜗牛（腹足纲）和水生软体动物也出现在当前间冰期，即全新世的开始。由于温暖的水和土壤，温泉可能有利于木质的冰川生态系统。这一新的早期树木生长的发现，结合了其他在 11000 年前之前在阿尔卑斯山西部存在树木的分散证据，改变了我们对冰缘环境中树木分布的看法，支持了在冰川海洋中存在无树冰原的观点。因此，白板范式必须重新审视，因为它对包括后冰期植物迁移和生物地球化学循环在内的全球变化有重要影响。
