Yukon ice patches: Bryophyte generation from ancient ice-entombed assemblages

In Southwestern Yukon, ice patches have shown substantial retreat since the Little Ice Age (1600–1900 AD) in response to warming trends. These ice patches support unique alpine wetlands that have formed habitats for diverse flora and fauna over millennia. With ice retreat, pristine bryophyte populations are exposed beneath accumulated ancient dung. Given that bryophytes have been shown to survive extreme conditions including ice entombment and can regenerate from viable cells, emergent ice margin bryophyte and dung samples from the Granger and Gladstone ice patches were assayed for regrowth potential under growth chamber conditions. Diaspore (spore/fragment) generation of species found in the original subfossil material was indicated in 68 percent of assays, emphasizing the cyclical establishment of ancient ice patch vegetation. One of the oldest samples, dating 4036 calibrated years BP from the Gladstone ice patch margin, showed remarkable bryophyte generation from diaspores in dung. These Yukon ice patches form reservoirs of cryopreserved biota and have a critical role in maintaining alpine diversity, which provides summer refuge for caribou and other alpine fauna. Ice margin fluctuations, which bury and release populations through time, are part of a complex revegetation sequence in alpine regions that has followed deglaciation.

在育空地区西南部，自小冰期（Little Ice Age，公元1600–1900年）以来，冰斑块（ice patches）因气候变暖趋势出现了显著消退。这些冰斑块孕育了独特的高山湿地，数千年来为多样的动植物群落提供了栖息生境。随着冰体消融，堆积在古代粪便层下的原始苔藓植物（bryophyte）种群得以出露。已有研究证实，苔藓植物可在包括冰封藏在内的极端环境中存活，并可通过活细胞实现再生。为此，研究人员对取自格兰杰（Granger）与格拉德斯通（Gladstone）冰斑块冰缘的苔藓植物及粪便样本，开展了人工气候箱（growth chamber）条件下的再生潜力测定。结果显示，68%的检测样本中，原亚化石（subfossil）材料内发现的物种可产生繁殖体（diaspore，即孢子/片段），这印证了古代冰斑块植被的周期性重建过程。其中一份来自格拉德斯通冰斑块冰缘的最古老样本，经校准年代距今达4036年，其粪便中的繁殖体可萌发形成苔藓植物，展现出极强的再生能力。育空地区的这些冰斑块是低温冷冻保存生物群落（cryopreserved biota）的储库，在维持高山生物多样性方面发挥着关键作用，并为驯鹿及其他高山动物提供了夏季庇护所。冰缘的周期性波动会随时间埋藏并释放种群，这是冰川消退后高山地区复杂的植被恢复序列的重要组成部分。