In Central Europe, forests are increasingly affected by various disturbances, resulting in an increasing gap formation in the canopy. In order to support goal-oriented management, more knowledge is required about the acclimation of the crown and its effects on the basal area growth of trees at the edge of a gap. This work compared trees' growth and crown structure at the edge of a transient gap, with a gap size of more than 80 ​m, with trees in the stand that were at least 30 ​m away from the gap. A total of 249 European beeches ( L.), Norway spruces ( L. Karst), Scots pines ( L.), oaks ( spp.; (Matt.) Liebl., L.), and silver firs ( Mill.) were examined on long-term experimental plots in southern Germany. Various crown measures were developed and calculated using high-resolution terrestrial laser scanning (TLiDAR) to capture the three-dimensional crown structures. Growth responses to edge conditions were measured based on tree rings. Using linear mixed models, we predict the basal area increment of edge trees relative to trees in the stand under wet and dry soil moisture conditions after the gap formation. We identified i) species-specific acclimation of the crown of edge trees after the gap formation, ii) under wet soil moisture conditions a growth increase of 25%–45% for beech, pine, and oak edge trees and growth losses of 5%–60% for spruce and fir and iii) coniferous tree species benefited from the edge position regarding their basal area increment under dry soil moisture conditions and deciduous tree species grew regardless of the soil moisture conditions at the edge of a gap. Gaps have a species-specific effect on the habitus and growth of edge trees and can have both positive and negative impacts on silviculture.

中文翻译：

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干旱条件下五种欧洲树种树冠异速生长和间隙边缘茎生长的差异调节


在中欧，森林越来越多地受到各种干扰的影响，导致树冠间隙越来越大。为了支持目标导向的管理，需要更多关于树冠的适应及其对间隙边缘树木断面积生长的影响的知识。这项工作比较了间隙尺寸超过 80 m 的临时间隙边缘的树木生长和树冠结构，以及距离间隙至少 30 m 的林分树木。总共 249 棵欧洲山毛榉 (L.)、挪威云杉 (L. Karst)、欧洲赤松 (L.)、橡树 ( spp.; (Matt.) Liebl., L.) 和银杉 (Mill.)在德国南部的长期试验田上进行了检查。使用高分辨率地面激光扫描 (TLiDAR) 开发和计算了各种牙冠测量值，以捕获三维牙冠结构。根据树木年轮测量对边缘条件的生长反应。使用线性混合模型，我们预测间隙形成后在潮湿和干燥土壤湿度条件下边缘树木相对于林分内树木的断面积增量。我们确定了 i) 间隙形成后边缘树冠的物种特异性驯化，ii) 在潮湿的土壤湿度条件下，山毛榉、松树和橡树边缘树的生长增加了 25%–45%，生长损失为 5%云杉和冷杉为 –60%，iii) 针叶树种在干燥土壤湿度条件下受益于其断面积增量的边缘位置，而落叶树种无论间隙边缘的土壤湿度条件如何都会生长。间隙对边缘树木的习性和生长具有特定物种的影响，并对造林产生积极和消极的影响。