Dong Jing-Jing, Wang Li, Niu Zheng
The State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing Applications, Chinese Academy of Sciences, Beijing 100101, China.
Guang Pu Xue Yu Guang Pu Fen Xi. 2009 Nov;29(11):3003-6.
Many researches have developed models to estimate chlorophyl content at leaf and canopy level, but they were species-specific. The objective of the present paper was to develop a new model. First, canopy reflectance was simulated for different species and different canopy architecture using radiative transfer models. Based on the simulated canopy reflectance, the relationship between canopy reflectance and canopy chlorophyll content was studied, and then a chlorophyll estimation model was built using the method of spectral index. The coefficient of determination (R2) between spectral index based model and canopy chlorophyll content reached 0.75 for simulated data. To investigate the applicability of this chlorophyll model, the authors chose a field sample area in Gansu Province to carry out the measurement of leaf chlorophyll content, canopy reflectance and other parameters. Besides, the authors also ordered the synchronous Hyperion data, a hyperspectral image with a spatial resolution of 30 m. Canopy reflectance from field measurment and reflectance from Hyperion image were respectively used as the input parameter for the chlorophyll estimation model. Both of them got good results, which indicated that the model could be used for accurate canopy chlorophyll estimation using canopy reflectance. However, while using spaceborne hyperspectral data to estimate canopy chlorophyll content, good atmospheric correction is required.
许多研究已经开发出模型来估计叶片和冠层水平的叶绿素含量，但这些模型是针对特定物种的。本文的目的是开发一种新模型。首先，使用辐射传输模型模拟了不同物种和不同冠层结构的冠层反射率。基于模拟的冠层反射率，研究了冠层反射率与冠层叶绿素含量之间的关系，然后使用光谱指数法建立了叶绿素估计模型。对于模拟数据，基于光谱指数的模型与冠层叶绿素含量之间的决定系数（R2）达到了0.75。为了研究该叶绿素模型的适用性，作者选择了甘肃省的一个野外采样区域，进行叶片叶绿素含量、冠层反射率和其他参数的测量。此外，作者还订购了同步的Hyperion数据，这是一幅空间分辨率为30米的高光谱图像。将野外测量的冠层反射率和Hyperion图像的反射率分别作为叶绿素估计模型的输入参数。两者都取得了良好的结果，这表明该模型可用于利用冠层反射率准确估计冠层叶绿素含量。然而，在使用星载高光谱数据估计冠层叶绿素含量时，需要进行良好的大气校正。
