估算混合植被叶绿素含量的理想波段分析

Optimal bands for estimation of mixed canopy chlorophyll content

应用Lopex数据库评价了19个波谱指数对物种的敏感性,分析了叶绿素含量与波谱反射率以及波谱导数的相关性,目的在于探寻对叶绿素含量变化的敏感性,对物种和叶片结构变化不敏感的理想波段,应用大尺度遥感数据估算混合植被冠层叶绿素含量。分析结果表明:红边指数对混合植被的叶绿素含量具有较好的指示作用;估算冠层叶绿素含量的理想波段为698—710nm附近较窄的波段范围;对于波谱导数,估算混合植被叶绿素含量的理想波段范围为720—735nm和535—550nm附近波谱导数。

A large number of spectral indices have been developed for estimation of leaf chlorophyll content. However, in most cases these indices have been tested for only one or at most a few related species, and thus it is not clear whether they can be applied across species with varying leaf structure characteristics. The main objective of the study is to find spectral bands that are sensitive to variation in chlorophyll content while relatively insensitive to species and leaf structure variation, determine optimal wide bands range for retrieving chlorophyll content of mixed canopies that consist of diverse species, and then develop wide-bands based approach to retrieve chlorophyll content of mixed canopies. We tested and compared 19 chlorophyll indices published on LOPEX93 （Leaf Optical Properties EXperiment 93） database to analyze the feasibility of using each of them as ＂universal＂ chlorophyll indices. Then the correlation between chlorophyll content and reflectance, the first derivative of reflectance spectra were studied based on LOPEX93 database, respectively. The results showed： （1） red edge spectral indices provided relatively good correlation with chlorophyll content when applied across a wide range of species; （2） the optimal band for esti- mation of chlorophyll content was found at 698-715nm range; （3） for the first derivative of reflectance, the optimal bands for estimation of chlorophyll content were at 720--735nm range and 535--550nm range.