依据LOPEX’93数据, 分别使用地表反射率光谱及其变化量以及光谱指数分析了鲜叶片叶绿素和水分含量的光谱响应。 结果表明, 在反射率光谱及其变化量的分析中, 反射率的二阶导数对叶绿素具有较高的响应, 对叶绿素响应较高的波段依次为600, 700, 670, 410, 490, 500和440 nm, 这些波段区间能够较好地反映植被叶绿素的含量; 反射率光谱经连续统去除后对叶片含水量具有较高的响应, 对水分含量响应较高的波段依次为: 1 870, 2 130, 2 180, 1 820, 2 350和2 120 nm, 分别对应着水分在短波红外波段的吸收波段。 在光谱指数的分析方法中, 光谱指数ND(normalized difference)对叶绿素含量较其他指数具有更高的响应, 其相关系数为0.618; 光谱指数Ratio975对叶片水分含量具有较高的响应, 相关系数可达0.996。 根据以上的响应分析, 构建相关模型, 对叶片中叶绿素和含水量开展地基反演实验, 结果表明, 基于地面光谱数据反演叶片中叶绿素和含水量可达到较高的精度。

Based on the leaf spectra data measured with LOPEX’93, the authors analyzed the relationship between leaf spectra and leaf biochemical components including leaf chlorophyll and leaf water content. It was showed that leaf chlorophyll was highly correlated with the second derivation of leaf reflectance at wavelengths 700, 670, 600, 500, 490, 440, and 410 nm; similarly, it was also showed that leaf water content was highly correlated with the continuum removed leaf reflectance at wavelengths 2 350, 2 180, 2 130, 2 120, 1 870, and 1 820 nm, which correspond to the absorption features of water in shortwave infrared bands. In addition, the authors found that ND(Normalized Difference) has a higher response to chlorophyll than other spectral indexes and the correlation coefficient is 0.618; Ratio975 has a very high response to water content and the correlation coefficient is up to 0.996. Based on the above evidences, the authors built a model to retrieve leaf chlorophyll and leaf water content through ground measured leaf spectra data and the simulated leaf chlorophyll and leaf water content are very accurate as compared to the ground measurements.