PREMISE Mountain ecosystems are particularly sensitive to climate change. However, only a very small number of studies exist so far using annually resolved records of alpine plant growth spanning the past century. Here we aimed to identify the effects of heat waves and drought, driven by global warming, on annual radial growth of Rhododendron ferrugineum. METHODS We constructed two century-long shrub ring-width chronologies from R. ferrugineum individuals on two adjacent, north- and west-facing slopes in the southern French Alps. We analyzed available meteorological data (temperature, precipitation and drought) over the period 1960-2016. Climate-growth relationships were evaluated using bootstrapped correlation functions and structural equation models to identify the effects of rising temperature on shrub growth. RESULTS Analysis of meteorological variables during 1960-2016 revealed a shift in the late 1980s when heat waves and drought increased in intensity and frequency. In response to these extreme climate events, shrubs have experienced significant changes in their main limiting factors. Between 1960 and 1988, radial growth on both slopes was strongly controlled by the sum of growing degree days during the snow free period. Between 1989 and 2016, August temperature and drought have emerged as the most important. CONCLUSIONS Increasing air temperatures have caused a shift in the growth response of shrubs to climate. The recently observed negative effect of high summer temperature and drought on shrub growth can, however, be buffered by topographic variability, supporting the macro- and microrefugia hypotheses.

中文翻译：

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有些（不）喜欢炎热：近几十年来，高山林线的高温和干旱阻碍了灌木的生长

前提 山区生态系统对气候变化特别敏感。然而，到目前为止，只有极少数研究使用跨越上个世纪的高山植物生长的年度解析记录。在这里，我们旨在确定由全球变暖驱动的热浪和干旱对铁杜鹃每年径向生长的影响。方法我们在法国南部阿尔卑斯山的两个相邻、朝北和朝西的斜坡上，从 R. ferrugineum 个体构建了两个世纪长的灌木环宽年表。我们分析了 1960-2016 年期间的可用气象数据（温度、降水和干旱）。使用自举相关函数和结构方程模型评估气候-生长关系，以确定温度升高对灌木生长的影响。结果 对 1960-2016 年气象变量的分析显示，在 1980 年代后期热浪和干旱的强度和频率增加时发生了变化。为应对这些极端气候事件，灌木的主要限制因素发生了重大变化。1960 年至 1988 年期间，两个斜坡的径向生长都受到无雪期生长期日数总和的强烈控制。1989 年至 2016 年，8 月的温度和干旱成为最重要的。结论 气温升高导致灌木生长对气候的反应发生了变化。然而，最近观察到的夏季高温和干旱对灌木生长的负面影响可以通过地形变异来缓冲，支持宏观和微型避难所假设。