Key message During the past decades, a multitude of oak stands have spontaneously established across the pine-dominated landscapes of the French Landes de Gascogne. Yet their future performance under modern climate change is unknown. We show that coppiced, dominant trees are most prepared to cope with drought episodes, displaying higher basal area increment and lower sensitivity to extreme events. Context Forest stands dominated by pedunculate oak ( Quercus robur L.) have spontaneously established across the pine-dominated landscapes of the French Landes de Gascogne. These oak stands are typically unmanaged and unsystematically coppiced, resulting in mixtures of single- and multi-stemmed (coppiced) trees. Aims To determine the ability of spontaneous oak forest stands to face climate change–related hazards, by analysing differences in growth (tree-ring width and basal area increment—BAI), wood density and climate sensitivity depending on their tree architecture (single- vs multi-stemmed trees) and their social status in the forest. Methods We exhaustively cored 15 oak stands ( n = 657 trees). We compared stand characteristics and climate sensitivity between tree architectures considering two sampling designs, either all sampled trees (the exhaustive sampling) or those with a dominant status (dominant sampling). At the tree level, we used linear mixed effects models to compare wood density and growth between tree architectures and the trees’ social status within the canopy layer (dominant- vs non-dominant trees). Results Multi-stemmed trees exhibited higher wood density than single-stemmed trees for diameters > 30 cm. Dominant multi-stemmed trees showed lower sensitivity to extreme events (pointer years), higher BAI but lower annual growth rates than dominant single-stemmed trees. Conclusion Dominant multi-stemmed trees are potentially the most prepared ones to cope with increasing soil water deficit following drought episodes, at least during the first 60 years of the life of the tree. The vulnerability to face harsher climate conditions for Q. robur stands can be misled when using a dominant sampling design.

中文翻译：

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在自发建立的橡树林中，社会地位和树木结构如何影响径向生长、木材密度和干旱反应？

关键信息 在过去的几十年里，在法国朗德加斯科涅以松树为主的景观中自发地建立了许多橡木林。然而，它们在现代气候变化下的未来表现尚不清楚。我们表明，被砍伐的优势树木最能应对干旱事件，表现出更高的基础面积增量和对极端事件的较低敏感性。背景 以有花序橡树 (Quercus robur L.) 为主的森林林分自发地建立在法国 Landes de Gascogne 以松树为主的景观中。这些橡木林通常不受管理且未系统地修剪，导致单茎和多茎（修剪）树木混合。目的 确定自发橡树林林分面对气候变化相关灾害的能力，通过分析生长（树轮宽度和基面积增量——BAI）、木材密度和气候敏感性的差异，这取决于它们的树结构（单茎树与多茎树）及其在森林中的社会地位。方法 我们详尽地对 15 个橡木林地（n = 657 棵树）进行了取芯。我们比较了考虑两种抽样设计的树木结构之间的林分特征和气候敏感性，无论是所有抽样的树木（穷举抽样）还是具有主导地位的树木（主导抽样）。在树木级别，我们使用线性混合效应模型来比较树木结构之间的木材密度和生长以及树冠层内树木的社会地位（优势树与非优势树）。结果 对于直径 > 30 cm 的多茎树木表现出比单茎树木更高的木材密度。与优势单茎树木相比，优势多茎树木对极端事件（指针年）的敏感性较低，BAI 较高，但年增长率较低。结论 优势多茎树木可能是应对干旱事件后土壤水分亏缺增加的准备最充分的树木，至少在树木生命的前 60 年是这样。当使用占主导地位的采样设计时，Q. robur 林分面临更恶劣的气候条件的脆弱性可能会被误导。