An improved method for the rapid assessment of forest understorey light environments
An improved method for the rapid assessment of forest understorey light environments
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DOI：
10.1046/j.1365-2664.2000.00573.x
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发表时间：
2000-12-01
影响因子：
5.7
通讯作者：
Nabe-Nielsen, J
中科院分区：
文献类型：
--
作者：
Brown, N;Jennings, S;Nabe-Nielsen, J
1. 森林林下光环境的高空间和时间变异性需要长时间和/或广泛的采样，以便通过直接测量来表征它。由于这通常是不切实际的，因此已经制定了许多替代措施，通过森林冠层结构的评估来估计光的可用性。2。 Clark & Clark (1992) 开发的主观树冠照度指数与 Garrison (1949) 的驼峰和两种新方法进行了比较：(i) 树冠照度椭圆法，将树冠间隙的大小与印刷在透明屏幕上的一系列标准面积椭圆进行比较；(ii) 树冠范围，与驼峰一样，使用印刷在透明屏幕上的 25 个点阵列来评估树冠开放性，但更坚固和便携，测量从测量点可见的最大冠层间隙，而不是头顶上的冠层开放度。3。与树冠照明指数相比，新测量值与冠层开放度（从半球照片测量到的 0-30% 范围内）的相关性更高，并且观察者之间的变异性水平较低。4。冠层范围有望广泛应用于森林林下光环境的简单快速评估。它的优点是提供可用于参数统计的比率尺度测量。头冠照明椭圆可用于对高于头部高度的头冠的照明进行评分。
1. The high spatial and temporal variability of forest understorey light environments requires lengthy and/or extensive sampling in order to characterize it by direct measurement. As this is often impractical, a number of surrogate measures have been developed that estimate light availability from assessments of forest canopy structure.2. The subjective crown illumination index developed by Clark & Clark (1992) was compared with Garrison's (1949) moosehorn and two new methods: (i) the crown illumination ellipses method, which compares the size of canopy gaps with a series of standard area ellipses printed on a transparent screen: and (ii) the canopy-scope that, like the moosehorn, uses an array of 25 dots printed on a transparent screen to assess canopy openness, but is more robust and portable, measuring the largest canopy gap visible from the point of measurement rather than canopy openness overhead.3. The new measures were more highly correlated with canopy openness in the range 0-30%, measured from hemispherical photographs, than the crown illumination index, and showed lower levels of between-observer variability.4. The canopy-scope has the potential to be widely used for the simple and rapid assessment of forest understorey light environments. It has the advantage of giving ratio scale measurements that can be used in parametric statistics. The crown illumination ellipses can be used to score the illumination of crowns that are above head height.