Relatively mesic environments within arid regions may be important conservation targets as 'climate change refugia' for species persistence in the face of worsening drought conditions. Semi-arid southern California and the relatively mesic environments of California's Channel Islands provide a model system for examining drought responses of plants in potential climate change refugia. Most methods for detecting refugia are focused on 'exposure' of organisms to certain abiotic conditions, which fail to assess how local adaptation or acclimation of plant traits (i.e. 'sensitivity') contribute to or offset the benefits of reduced exposure. Here, we use a comparative plant hydraulics approach to characterize the vulnerability of plants to drought, providing a framework for identifying the locations and trait patterns that underlie functioning climate change refugia. Seasonal water relations, xylem hydraulic traits and remotely sensed vegetation indices of matched island and mainland field sites were used to compare the response of native plants from contrasting island and mainland sites to hotter droughts in the early 21st century. Island plants experienced more favorable water relations and resilience to recent drought. However, island plants displayed low plasticity/adaptation of hydraulic traits to local conditions, which indicates that relatively conserved traits of island plants underlie greater hydraulic safety and localized buffering from regional drought conditions. Our results provide an explanation for how California's Channel Islands function as a regional climate refugia during past and current climate change and demonstrate a physiology-based approach for detecting potential climate change refugia in other systems.

中文翻译：

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植物的水力特征表明，干旱加剧使岛屿成为避难所。

干旱地区内相对较复杂的环境可能是重要的保护目标，因为面对干旱条件不断恶化，物种生存的“气候变化避难所”。半干旱的加利福尼亚南部和加利福尼亚海峡群岛的相对较陡的环境为检查潜在气候变化避难所中植物的干旱反应提供了一个模型系统。大多数检测避难所的方法都集中于使生物“暴露”于某些非生物条件下，而这些条件无法评估局部适应或适应植物性状（即“敏感性”）如何促进或抵消减少暴露的益处。在这里，我们使用比较植物水力学方法来表征植物对干旱的脆弱性，提供一个框架，以识别正在起作用的气候变化避难所的位置和特征模式。利用季节性水关系，木质部水力特性和匹配的岛屿和大陆田地的遥感植被指数，来比较21世纪初来自岛屿和大陆不同地区的本地植物对炎热干旱的响应。岛屿植物与水的关系更加有利，并且对最近的干旱具有一定的抵抗力。然而，岛屿植物显示出较低的可塑性/使水力性状适应当地条件，这表明相对保守的岛屿植物性状具有较高的水力安全性和局部干旱条件的局部缓冲作用。我们的结果为加利福尼亚州如何“