ABSTRACT

The spectral characteristics of sunlit and shaded leaves are critical to improving the utilization of remote sensing methodology to quantify forest physiology. However, spectral characteristics within the tree canopies, especially normalized difference vegetation index (NDVI) and photochemical reflectance index (PRI), are poorly understood. Our study used an imaging observation platform to obtain hyperspectral imagery of a Manchurian Ash canopy on Changbai Mountain. A non-imaging spectrometer was employed for an assisted analysis. The study results of the corresponding spectrum obtained at two observation spatial scales were significantly different between sunlit and shaded leaves. For imaging spectral observations, there were significant differences in NDVI and PRI between sunlit and shaded leaves (P < 0.001). PRI near the petiole was significantly lower than in other parts of leaves (P = 0.049). Non-imaging spectral observations of the reflectance of sunlit and shaded leaves were different only in the visible light region. The PRI of the shaded leaves were higher than that of sunlit leaves, which was consistent with the imaging spectral observations. The complexity of light environment within the canopy, especially the differences in incident irradiance, contributed to the range of leaf attribute measurements, which resulted in the variability of spectral characteristics.

摘要

光照和阴影叶子的光谱特征对于提高利用遥感方法量化森林生理学至关重要。然而，人们对树冠内的光谱特征，特别是归一化差异植被指数（NDVI）和光化学反射指数（PRI）知之甚少。我们的研究使用成像观测平台获得了长白山白蜡树冠层的高光谱图像。使用非成像光谱仪进行辅助分析。在两个观测空间尺度上获得的相应光谱的研究结果在阳光照射和遮光的叶子之间存在显着差异。对于成像光谱观测，阳光照射和阴影叶子之间的 NDVI 和 PRI 存在显着差异（P< 0.001)。叶柄附近的PRI显着低于叶片其他部位（P  =0.049）。对阳光照射和阴影叶子的反射率的非成像光谱观察仅在可见光区域有所不同。遮光叶片的PRI高于光照叶片，这与成像光谱观测结果一致。冠层内光环境的复杂性，特别是入射辐照度的差异，影响了叶片属性测量的范围，从而导致光谱特征的可变性。