Canopy gaps affect the shape of Douglas-fir crowns in the western Cascades, Oregon
Canopy gaps affect the shape of Douglas-fir crowns in the western Cascades, Oregon
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DOI：
10.1016/j.foreco.2015.12.024
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发表时间：
2016-03-01
影响因子：
3.7
通讯作者：
Puettmann, Klaus
中科院分区：
文献类型：
--
作者：
Seidel, Dominik;Ruzicka, Kenneth J.;Puettmann, Klaus
旨在增加林分结构多样性的造林制度通常会促进水平和垂直结构的小规模异质性，例如通过创造间隙。我们使用地面激光扫描（TLS）来研究生长条件改变对人工间隙附近树木的影响，并与规则间隔的稀疏森林内部树木的反应进行比较。基于基于 TLS 的点云，我们计算了许多树冠结构特性，假设这些特性对生长条件的空间变化敏感。我们发现两种生长条件下树木的结构特性之间存在一些显着差异。与规则间距的树木相比，间隙附近的边界树木具有较低的冠基高度（CBH）和较低的最大冠投影高度。边境树的树冠表面积和树冠体积均显着大于规则间距的树。此外，边界树的整个树冠，特别是树冠的下三分之一的不对称性，都指向间隙中心，反映了间隙中增加的光照水平。我们的研究结果引起了人们的担忧，即边界树的经济价值受到间隙产生的负面影响。这些树的无枝树干较短，此外，由于水平枝伸长，树节较大。相反，由人工间隙林分中的边界树木造成的结构变异性的总体增加可能会对多种生态系统功能以及生物多样性产生积极影响。 (C) 2015 Elsevier B.V. 保留所有权利。
Silvicultural regimes that aim at an increased stand structural diversity typically promote small-scale heterogeneity in horizontal and vertical structures, e.g. through the creation of gaps. We used terrestrial laser scanning (TLS) to investigate impacts of altered growing conditions on trees adjacent to artificial gaps as compared to responses of trees in a regularly spaced, thinned forest interior. Based on the TLS based point clouds we calculated a number of structural tree crown properties that were hypothesized to be sensitive to spatial variability in growing conditions. We found several significant differences between structural properties of trees in the two growing conditions. Compared to trees in regular spacing, border trees near gaps had a lower crown base height (CBH) and a lower height of maximum crown projection. Crown surface area and crown volume of border trees were significantly larger than those of trees growing in a regular spacing. Also, the asymmetry of entire tree crowns of border trees, and in particular of the lower third of crowns, was directed towards the gap center, reflecting the increased light level in the gap. Our results raise concerns that the economic value of border trees is negatively affected by gap creation. These trees had shorter branch free boles and additionally, due to horizontal branch elongation, larger knots. Conversely, the overall increase in structural variability contributed by the border trees in stands with artificial gaps is likely to positively affect several ecosystem functions as well as biodiversity. (C) 2015 Elsevier B.V. All rights reserved.