叶片茸毛对叶片反射光谱及高光谱植被指数的影响研究

很多高光谱植被指数被用于对植被的生化物质含量进行非破坏性的估计与反演。由于这些指数都是利用不同波段的反射率计算而得到的,因而对叶片反射具有很大影响的茸毛等叶表结构对这些植被指数的反演精度的影响不容忽视。本研究发现去茸毛处理使得在400～1 000nm范围的的光谱反射都有所下降,但在各个波段的变化并不均匀。通过对比39个现有的高光谱植被指数在经过去茸毛处理前后的变化,发现一些只单独利用可见光或者近红外波段的高光谱植被指数,如CTR1:R695/R420,D740/D720,WBI:R900/R970,R860/(R550×R708)以及红边指数(REP)比大多数既使用可见光又使用近红外波段的高光谱植被指数受茸毛变化影响小,它们对茸毛的低敏感性可以使其在进行植被生化物质反演时更具有普适性。

Effects of leaf hair on leaf reflectance and hyperspectral vegetation indices

Many hyperspectral vegetation indices have been used to estimate the biochemical contents such as pigment content, nondestructively. These reflectance indices are influenced by leaf hair, and the existence of the leaf hair affects the performance of the indices on the estimation of the biochemical contents. The present research studied the possible effects of the leaf hair on the reflectance of the same leaf before and after removal of leaf hair. The authors found that dehairing had decreased the reflectance between wavelength 400 and 1 000 nm, and the decrease depends on the wavelength. The changes of 39 hyperspectral indices before and after the hair removal were compared. The results revealed that some indices that only use visible wavebands or the near infrared wavebands such as CTR1: R695/R420, D740/D720, WBI: R900/R970, R860/(R550 x R708) and REP (Red-edge position) were not affected much by the dehairing process and are thought relatively robust to estimate the biochemical contents.