Developing Hyperspectral Indices for Assessing Seasonal Variations in the Ratio of Chlorophyll to Carotenoid in Deciduous Forests
Developing Hyperspectral Indices for Assessing Seasonal Variations in the Ratio of Chlorophyll to Carotenoid in Deciduous Forests
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DOI：
10.3390/rs14061324
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发表时间：
2022-03
期刊：
影响因子：
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通讯作者：
Guangman Song;Quan Wang
中科院分区：
文献类型：
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作者：
Guangman Song;Quan Wang
叶片色素对各种胁迫条件和衰老阶段敏感。叶绿素与类胡萝卜素含量比值的变化为了解落叶林植物的生理和物候状态提供了有价值的见解。虽然使用光谱指数来评估这一比例已经尝试过，几乎所有的指数间接来自叶绿素和类胡萝卜素含量的开发。此外，一直很少关注的比例，这是一个很好的代理叶片衰老的季节动态，导致只有少数研究以往任何时候都在跟踪的比例在整个生长季节使用光谱指数。在这项研究中，我们开发了一种新的高光谱指数跟踪的比率在落叶林的季节变化，基于一个复合数据集的两个实地测量数据集从日本和一个公开的数据集（昂热）。在此过程中采用了各种光谱变换，以确定最可靠的高光谱指数。结果表明，波长差（D）类型指数，使用540和1396 nm的波长（计算转换光谱，通过扩展的乘法散射校正（EMSC）和一阶导数的组合进行预处理），表现出最高的精度为叶绿素/类胡萝卜素的比例估计（R2 = 0.57，RPD = 1.52）。进一步的评估表明，该指数保持了良好的性能在不同的季节阶段，可以被认为是一个有用的代理落叶物种的比例。这些研究结果为高光谱信息在植被功能评估中的应用提供了基础。虽然有前途，广泛的评价建议的指数仍然需要其他功能类型的植物。
Leaf pigments are sensitive to various stress conditions and senescent stages. Variation in the ratio of chlorophyll to carotenoid content provides valuable insights into the understanding of the physiological and phenological status of plants in deciduous forests. While the use of spectral indices to assess this ratio has been attempted previously, almost all indices were derived indirectly from those developed for chlorophyll and carotenoid contents. Furthermore, there has been little focus on the seasonal dynamics of the ratio, which is a good proxy for leaf senescence, resulting in only a few studies ever being carried out on tracing the ratio over an entire growing season by using spectral indices. In this study, we developed a novel hyperspectral index for tracing seasonal variations of the ratio in deciduous forests, based on a composite dataset of two field measurement datasets from Japan and one publicly available dataset (Angers). Various spectral transformations were employed during this process in order to identify the most robust hyperspectral index. The results show that the wavelength difference (D) type index, using wavelengths of 540 and 1396 nm (calculated from the transformed spectra that were preprocessed by the combination of extended multiplicative scatter correction (EMSC) and first-order derivative), exhibited the highest accuracy for the estimation of the chlorophyll/carotenoid ratio (R2 = 0.57, RPD = 1.52). Further evaluation revealed that the index maintained a good performance at different seasonal stages and can be considered a useful proxy for the ratio in deciduous species. These findings provide a basis for the usage of hyperspectral information in the assessment of vegetation functions. Although promising, extensive evaluations of the proposed index are still required for other functional types of plants.