Smolander H., Stenberg P., Linder S.
The Finnish Forest Research Institute, Suonenjoki Research Station, SF-77600 Suonenjoki, Finland.
Tree Physiol. 1994 Jul-Sep;14(7_9):971-980. doi: 10.1093/treephys/14.7-8-9.971.
The ratio of shoot silhouette area to total needle area (STAR) is one means of quantifying the light interception efficiency of a coniferous shoot. The silhouette area (or STAR) of a shoot depends on various structural characteristics of the shoot, and also varies with the direction of the shoot relative to the direction of radiation (sun angle). The mean STAR taken over all directions in space is the mean ratio of shoot silhouette area to total needle area in an isotropic radiation field. It also represents a mean STAR with respect to a spherical shoot orientation. In this study, equations for the relationship between mean STAR and easily measurable shoot characteristics were developed. The STAR values in different directions were determined from photographically measured shoot silhouette areas. Mean STAR varied between 0.079 and 0.308, and averaged 0.146. A clear increase in mean STAR with age was found. The material consisted of 305 Scots pine (Pinus sylvestris L.) shoots from Sweden and Finland, representing shoots of different age and a wide variation in site fertility. The needle area density in the shoot cylinder, together with the diameters of the shoot cylinder and the twig explained 87% of the variation in mean STAR.
枝梢轮廓面积与针叶总面积之比（STAR）是量化针叶树枝梢光截获效率的一种方法。枝梢的轮廓面积（或STAR）取决于枝梢的各种结构特征，并且还会随着枝梢相对于辐射方向（太阳角度）的方向而变化。在空间所有方向上获取的平均STAR是在各向同性辐射场中枝梢轮廓面积与针叶总面积的平均比值。它也代表了相对于球形枝梢取向的平均STAR。在本研究中，建立了平均STAR与易于测量的枝梢特征之间关系的方程。通过摄影测量的枝梢轮廓面积确定不同方向上的STAR值。平均STAR在0.079至0.308之间变化，平均为0.146。发现平均STAR随年龄明显增加。材料包括来自瑞典和芬兰的305个苏格兰松（Pinus sylvestris L.）枝梢，代表不同年龄的枝梢以及立地肥力的广泛差异。枝梢圆柱体中的针叶面积密度，连同枝梢圆柱体和小枝的直径，解释了平均STAR变化的87%。
