植被叶片光谱及红边特征与叶片生化组分关系的分析
Relational analysis of spectra and red-edge characteristics of plant leaf and leaf biochemical constituent
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摘要: 以LOPEX’93数据集为基础, 利用最新的叶片光学模型——PROSPECT5模型模拟了不同生化组分(叶肉结构参数、等效水厚、叶绿素、类胡萝卜素和干物质)含量叶片的反射率、透射率和吸收率光谱, 并在此基础上提取植被红边特征, 系统分析光谱和叶片生化组分的关系, 建立光谱特征与叶片生化组分的关系模型, 为生化组分反演提供一定的理论基础。结果表明, 在可见光部分, 叶片的光谱主要取决于叶肉结构参数和色素(叶绿素和类胡萝卜素); 在红外波段, 叶片的光谱主要受水分、叶肉结构参数和干物质含量的影响。不同的波段范围内, 光谱对生化组分的敏感度不同。叶片的红边特征不受水分和类胡萝卜素的影响, 但红边位置随叶绿素的增加向长波方向移动(红移)。红边斜率随内部结构参数的增加而增加, 两者之间的关系可用二次方程描述, 这为叶肉结构参数的求解提供了一个方向。Abstract: Using LOPEX’93 dataset, this paper simulated spectra reflectance, transmittance and absorptance of plant leaves under different biochemical constituents of leaf mesophyll structure parameter, water, chlorophyll, carotenoids and dry matter. The newest PROSPECT5 (leaf optical properties spectra) model was used for relational analysis of spectra and biochemical constituents as detected by vegetation remote sensing, on the basis of which red-edge characteristics were determined. The research task was to establish a model relating biochemical constituents to spectral characteristics via systematic relational analysis. Biochemical constituents of plant leaf should be inverted by the model. The results show that visible range of leaf spectra mainly depend on leaf mesophyll structure parameter and pigment (including chlorophyll and carotenoid). In the infrared range, leaf spectra largely depend on water, leaf mesophyll structure parameter and dry matter. Red-edge position moves towards long-wave with increasing chlorophyll, the so-called red-shift. Red-edge characteristics are not affected by water and carotenoid, and red-edge slope increases with increasing leaf mesophyll structure parameter. These relations are perfectly describable by di-order fitting equations. This lays the basis for solving mesophyll structure parameter issues.