Chen J M, Cihlar J
Appl Opt. 1995 Sep 20;34(27):6211-22. doi: 10.1364/AO.34.006211.
Optical instruments currently available for measuring the leaf-area index (LAI) of a plant canopy all utilize only the canopy gap-fraction information. These instruments include the Li-Cor LAI-2000 Plant Canopy Analyzer, Decagon, and Demon. The advantages of utilizing both the canopy gap-fraction and gap-size information are shown. For the purpose of measuring the canopy gap size, a prototype sunfleck-LAI instrument named Tracing Radiation and Architecture of Canopies (TRAC), has been developed and tested in two pure conifer plantations, red pine (Pinus resinosa Ait.) and jack pine (Pinus banksiana Lamb). A new gap-size-analysis theory is presented to quantify the effect of canopy architecture on optical measurements of LAI based on the gap-fraction principle. The theory is an improvement on that of Lang and Xiang [Agric. For. Meteorol. 37, 229 (1986)]. In principle, this theory can be used for any heterogeneous canopies.
目前可用于测量植物冠层叶面积指数（LAI）的光学仪器都仅利用冠层间隙率信息。这些仪器包括Li-Cor LAI-2000植物冠层分析仪、Decagon和Demon。研究表明了同时利用冠层间隙率和间隙大小信息的优势。为了测量冠层间隙大小，已开发出一种名为“冠层辐射追踪与结构分析”（TRAC）的太阳光斑-LAI原型仪器，并在两个纯针叶林种植园——红松（Pinus resinosa Ait.）和短叶松（Pinus banksiana Lamb）中进行了测试。提出了一种新的间隙大小分析理论，以基于间隙率原理量化冠层结构对LAI光学测量的影响。该理论是对Lang和Xiang [Agric. For. Meteorol. 37, 229 (1986)]理论的改进。原则上，该理论可用于任何非均匀冠层。
