植物学报 ›› 2008, Vol. 25 ›› Issue (06): 714-721.

• 实验简报 • 上一篇    下一篇

基于辐射传输模型的高光谱植被指数与叶绿素浓度及叶面积指数的线性关系改进

吴朝阳1, 2*, 牛铮1   

  1. 1中国科学院遥感应用研究所遥感科学国家重点实验室, 北京 100101; 2中国科学院研究生院, 北京 100039
  • 收稿日期:2008-04-10 修回日期:2008-06-26 出版日期:2008-11-01 发布日期:2010-10-18
  • 通讯作者: 吴朝阳

Improvement in Linearity Between Hyperspectral Vegetation Indices and Chlorophyll Content, Leaf Area Index Based on Radiative Transfer Models

Chaoyang Wu1, 2*, Zheng Niu1   

  1. 1The State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing Applications, Chinese Academy of Sciences, Beijing 100101, China; 2Graduate School of Chinese Academy of Sciences, Beijing 100039, China
  • Received:2008-04-10 Revised:2008-06-26 Online:2008-11-01 Published:2010-10-18
  • Contact: Chaoyang Wu

摘要: 高光谱植被指数以其特有的精细光谱特征, 能够获得非常细微的植被生理状况和环境胁迫差异, 因而使遥感技术在精细农业中的应用, 尤其是在叶绿素浓度和叶面积指数的反演上面有着广阔的应用前景。然而, 现有的植被指数往往和这2个参数呈非线性关系, 且只对某一区间的数值敏感, 无法适用于其它植被覆盖程度的研究。为了寻找合适的波段位置以改善植被指数与叶绿素浓度和叶面积指数的线性关系, 去除饱和区域, 进而提高这2个参数的实际估算精度, 该文选取了叶绿素浓度和叶面积指数, 以辐射传输模型PROSPECT和SAIL为基础, 模拟了这2个参数变化对3类高光谱植被指数(归一化植被指数(NDVI)、 优化的简单比值指数(MSR)和优化的叶绿素吸收率指数(MCARI))的影响。叶绿素浓度变化敏感性分析结果表明, 对这3类植被指数而言, 750 nm 和705 nm 的叶片反射率更适合实际的叶绿素浓度反演。以750 nm 和705 nm代替 800 nm/700 nm 和670 nm成功地提高了3类植被指数与叶绿素浓度的线性相关程度, 其中MCARI705 和叶绿素浓度基本呈线性关系。叶面积指数变化敏感性分析同样显示, 以750 nm 和705 nm 组成的植被指数能够获取更可靠的叶面积指数信息, 尤其对于高植被覆盖区域。其中MCARI705 能较好地降低随叶面积指数变化的饱和程度, 相比其它植被指数, 当叶面积指数大于8时, MCARI705 才出现明显的饱和。由于冠层的尺度效应, 波段位置的选择对植被指数与叶面积指数线性关系的改善不及对叶绿素浓度明显。

Abstract: Hyperspectral vegetation indices, which have fine spectra, can be used to detect the subtle physiological and environmental changes in vegetation. Therefore, use of the indices opens up an avenue for precise measurement for agriculture, especially for chlorophyll levels and leaf area index. However, a number of vegetation indices are not linearly related to biochemical components, so these indices may not be appropriate for other vegetative areas. We selected two different scale parameters, leaf chlorophyll content and leaf area index, on the basis of the radiative transfer models PROSPECT and SAIL, respectively, for sensitivity study of a set of indices (NDVI, MSR and MCARI). We aimed to improve the linearity between the indices for chlorophyll content and leaf area index on the basis of combinations of different wave bands. The sensitivity study of chlorophyll content revealed that for all the three kinds of indices, replacing the reflectance of 800 nm/700 nm and 670 nm with 750 nm and 705 nm, respectively can successfully improve the linearity limits of all vegetation indices. A nearly linear relationship is achieved between the index of MCARI705 and the chlorophyll content. Sensitivity study of leaf area index revealed that the index of MCARI705 can better alleviate the saturation problem of leaf area index changes. On comparing other indices, an obvious saturated region emerges for MCARI705 only when leaf area index exceeds 8. In general, different waveband selection (replacing 800 nm/700 nm and 670 nm with 750 nm and 705 nm, respectively) does not guarantee improvement of the linearity of indices with increased leaf area index as compared with chlorophyll content because of the complicated structure of the canopy.