Tropical montane forests are being lost at an alarming rate but harbor some of the globe’s most unique biodiversity. The Hawaiian archipelago is a prime example of the importance of high elevation forests to species conservation and persistence as they serve as the last refugia for Hawaiian birds. Yet these forests have been converted to invasive dominated pastures, and efforts to restore them have been met with limited success. Unsuccessful forest restoration may be due to freezing temperatures acting as a demographic bottleneck by killing seedlings recruiting into pastures. We determined freezing tolerances of eight common native woody plants at a high-elevation forest on Hawaiʻi Island and compared these freezing tolerances to two years of site-specific winter temperatures and 17 years of regional temperature records. Low temperature extremes were more severe and common in pastures than under nearby 30-year-old canopy trees. Freezing temperatures over two years were severe enough to damage leaf tissues of six of eight species tested. Those species that displayed the greatest freezing tolerance were also those found naturally recruiting into open pastures. Temperature trends over the past 17 years show monthly minimum temperatures are not increasing as predicted by climate change. Persistent severe freezing events may limit seedling recruitment in the pasture, slowing native woody plant expansion into these abandoned pastures. The species-level differences in freezing tolerance show that current management actions are using species that are at high risk to freezing damage outside of the forest canopy and that alternative species may warrant consideration.

热带山地森林正在以惊人的速度消失，但蕴藏着一些全球最独特的生物多样性。夏威夷群岛是高海拔森林对物种保护和持久性的重要例子，因为它们是夏威夷鸟类的最后避难所。然而，这些森林已转变为以入侵为主的牧场，恢复它们的努力取得了有限的成功。森林恢复失败可能是由于冻结温度杀死了进入牧场的幼苗造成的人口瓶颈。我们确定了夏威夷岛高海拔森林中八种常见原生木本植物的耐寒性，并将这些耐寒性与两年现场特定冬季温度和17年区域温度记录进行了比较。与附近的30岁树冠树相比，低温极端现象在牧场中更为严重和普遍。两年以上的冷冻温度足以破坏八种被测物种中六种的叶子组织。那些表现出最大耐寒性的物种也是那些自然招募到露天牧场的物种。过去17年的温度趋势显示，每月最低温度并未像气候变化所预测的那样增加。持续的严重冻结事件可能会限制草场中幼苗的募集，从而减慢本地木本植物向这些废弃草场的扩展。物种在耐寒性方面的差异表明，当前的管理措施所使用的物种极有可能在森林林冠层之外冷冻破坏，因此可能需要考虑其他物种。