Université Clermont Auvergne, CNRS, GEOLAB, F-63000 Clermont-Ferrand, France.
Université Clermont Auvergne, CNRS, GEOLAB, F-63000 Clermont-Ferrand, France.
Sci Total Environ. 2017 May 15;586:1020-1031. doi: 10.1016/j.scitotenv.2017.02.083. Epub 2017 Feb 15.
Rhododendron ferrugineum L. is a widespread dwarf shrub species growing in high-elevation, alpine environments of the Western European Alps. For this reason, analysis of its growth rings offers unique opportunities to push current dendrochronological networks into extreme environments and way beyond the treeline. Given that different species of the same genus have been successfully used in tree-ring investigations, notably in the Himalayas where Rhododendron spp. has proven to be a reliable climate proxy, this study aims at (i) evaluating the dendroclimatological potential of R. ferrugineum and at (ii) determining the major limiting climate factor driving its growth. To this end, 154 cross-sections from 36 R. ferrugineum individuals have been sampled above local treelines and at elevations from 1800 to 2100masl on northwest-facing slopes of the Taillefer massif (French Alps). We illustrate a 195-year-long standard chronology based on growth-ring records from 24 R. ferrugineum individuals, and document that the series is well-replicated for almost one century (1920-2015) with an Expressed Population Signal (EPS) >0.85. Analyses using partial and moving 3-months correlation functions further highlight that growth of R. ferrugineum is governed by temperatures during the growing season (May-July), with increasingly higher air temperatures favoring wider rings, a phenomenon which is well known from dwarf shrubs growing in circum-arctic tundra ecosystems. Similarly, the negative effect of January-February precipitation on radial growth of R. ferrugineum, already observed in the Alps on juniper shrubs, is interpreted as a result of shortened growing seasons following snowy winters. We conclude that the strong and unequivocal signals recorded in the fairly long R. ferrugineum chronologies can indeed be used for climate-growth studies as well as for the reconstruction of climatic fluctuations in Alpine regions beyond the upper limits of present-day forests.
高山柳叶杜鹃（Rhododendron ferrugineum L.）是一种广泛分布的矮灌木物种，生长在西欧阿尔卑斯山高海拔、高山的环境中。因此，分析其生长环提供了将当前树木年代学网络推向极端环境并超越树线的独特机会。鉴于同一属的不同物种已成功用于树木年轮研究，特别是在喜马拉雅山，那里的杜鹃属植物已被证明是一种可靠的气候代用指标，本研究旨在：（i）评估高山柳叶杜鹃的树木年代学潜力；（ii）确定驱动其生长的主要限制气候因素。为此，在法国阿尔卑斯山塔耶费尔山（Taillefer massif）西北坡，在当地树线以上和海拔 1800 至 2100 米的位置，从 36 株高山柳叶杜鹃个体中采集了 154 个横截面。我们展示了一个基于 24 株高山柳叶杜鹃个体的生长环记录的 195 年标准年表，并记录到该系列在近一个世纪（1920-2015 年）内具有良好的复制性，扩展人口信号（EPS）>0.85。使用偏相关和移动 3 个月相关函数的分析进一步强调，高山柳叶杜鹃的生长受生长季节（5 月至 7 月）温度的控制，随着气温升高，树木的生长速度加快，形成更宽的生长环，这一现象在生长于北极冻原生态系统中的矮灌木中已经得到证实。同样，1 月至 2 月降水对高山柳叶杜鹃径向生长的负影响，在阿尔卑斯山的杜松灌木上已经观察到，这被解释为冬季多雪导致生长季节缩短的结果。我们得出结论，在相当长的高山柳叶杜鹃年表中记录的强而明确的信号确实可用于气候-生长研究，以及重建阿尔卑斯山地区超出现有森林上限的气候波动。
