Gspaltl Martin, Bauerle William, Binkley Dan, Sterba Hubert
Institute of Forest Growth, University of Natural Resources and Life Sciences (BOKU), Vienna, Peter Jordan Strasse 82, 1190 Vienna, Austria.
Department of Horticulture and Landscape Architecture, Colorado State University, Fort Collins, CO 80523, USA.
For Ecol Manage. 2013 Jan 15;288:49-59. doi: 10.1016/j.foreco.2011.11.044.
Silviculture focuses on establishing forest stand conditions that improve the stand increment. Knowledge about the efficiency of an individual tree is essential to be able to establish stand structures that increase tree resource use efficiency and stand level production. Efficiency is often expressed as stem growth per unit leaf area (leaf area efficiency), or per unit of light absorbed (light use efficiency). We tested the hypotheses that: (1) volume increment relates more closely with crown light absorption than leaf area, since one unit of leaf area can receive different amounts of light due to competition with neighboring trees and self-shading, (2) dominant trees use light more efficiently than suppressed trees and (3) thinning increases the efficiency of light use by residual trees, partially accounting for commonly observed increases in post-thinning growth. We investigated eight even-aged Norway spruce ( (L.) Karst.) stands at Bärnkopf, Austria, spanning three age classes (mature, immature and pole-stage) and two thinning regimes (thinned and unthinned). Individual leaf area was calculated with allometric equations and absorbed photosynthetically active radiation was estimated for each tree using the three-dimensional crown model Maestra. Absorbed photosynthetically active radiation was only a slightly better predictor of volume increment than leaf area. Light use efficiency increased with increasing tree size in all stands, supporting the second hypothesis. At a given tree size, trees from the unthinned plots were more efficient, however, due to generally larger tree sizes in the thinned stands, an average tree from the thinned treatment was superior (not congruent in all plots, thus only partly supporting the third hypothesis).
造林学着重于营造能提高林分生长量的林分条件。了解单株树木的效率对于建立能够提高树木资源利用效率和林分水平产量的林分结构至关重要。效率通常表示为单位叶面积的干材生长量（叶面积效率），或单位吸收光量（光能利用效率）。我们检验了以下假设：（1）材积生长量与树冠光吸收的关系比与叶面积的关系更密切，因为由于与相邻树木的竞争和自我遮荫，单位叶面积可接收不同量的光；（2）优势木比被压木更有效地利用光；（3）间伐提高了保留木的光能利用效率，部分解释了间伐后常见的生长增加现象。我们调查了奥地利贝恩科夫的8个同龄挪威云杉（(L.) Karst.）林分，涵盖三个年龄级（成熟、未成熟和杆材级）和两种间伐方式（间伐和未间伐）。利用异速生长方程计算单株叶面积，并使用三维树冠模型Maestra估算每棵树吸收的光合有效辐射。光合有效辐射对材积生长量的预测仅略优于叶面积。在所有林分中，光能利用效率随树木大小增加而提高，支持了第二个假设。在给定树木大小的情况下，未间伐样地的树木效率更高，然而，由于间伐林分中树木通常更大，间伐处理的平均树木更优（并非在所有样地都一致，因此仅部分支持第三个假设）。
