Trees are able to adapt to changing environmental conditions through modifications in their crown morphology and branch architecture. In light-limited environments, tree structures are mainly optimised to increase light interception. This might have side effects on other properties such as the hydraulic system that determines water conduction and tree reactions to drought events. Given the increasing exposure of forest ecosystems to drought stress it is thus crucial to investigate possible correlations between the crown morphology and branch architecture and drought responses. Our study aimed to compare different crown archetypes and branch characteristics of European beech (Fagus sylvatica L.) in their reaction to drought, which was assessed by measuring tree-ring widths of increment cores sampled at breast height. Using Terrestrial Laser Scanning and Quantitative Structure Models, we explored various crown morphological and branch architectural characteristics of 67 beech trees and identified three species-specific crown archetypes. The crown archetypes and branch variables were contrasted with growth responses using linear mixed models. While productivity levels differed, the negative impact of drought stress on radial growth was consistent across all crown archetypes. Nevertheless, certain branch architectural variables were important predictors for radial growth in drought situations. Specifically, long water conduction paths and many branching nodes along those paths were positively influencing growth. Our results indicate that trees showing these characteristics might have a competitive edge regarding drought-affected radial growth compared to others. They could be promoted through thinning measures, which would allow improving the adaption of existing beech forests in situ to climate change and drought stress.

中文翻译：

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树冠形态和枝条结构对受干旱影响的 Fagus sylvatica L. 树木径向生长的影响


树木能够通过改变其树冠形态和树枝结构来适应不断变化的环境条件。在光线受限的环境中，树木结构主要经过优化以增加光线拦截。这可能会对其他特性产生副作用，例如确定水传导的液压系统和树木对干旱事件的反应。鉴于森林生态系统越来越容易受到干旱胁迫的影响，因此研究树冠形态和树枝结构与干旱响应之间可能存在的相关性至关重要。我们的研究旨在比较欧洲山毛榉 （Fagus sylvatica L.） 对干旱的反应中不同的树冠原型和分支特征，通过测量在胸高取样的增量核心的树木年轮宽度来评估。使用地面激光扫描和定量结构模型，我们探索了 67 棵山毛榉树的各种树冠形态和树枝结构特征，并确定了三种物种特异性树冠原型。使用线性混合模型将牙冠原型和分支变量与生长反应进行对比。虽然生产力水平不同，但干旱胁迫对径向生长的负面影响在所有树冠原型中都是一致的。尽管如此，某些分支结构变量是干旱情况下径向生长的重要预测因子。具体来说，较长的水传导路径和沿这些路径的许多分支节点对生长产生了积极影响。我们的结果表明，与其他树木相比，表现出这些特征的树木在受干旱影响的径向生长方面可能具有竞争优势。 它们可以通过间伐措施来促进，这将允许改善现有山毛榉林对气候变化和干旱胁迫的适应能力。