An Automated Comparative Observation System for Sun-Induced Chlorophyll Fluorescence of Vegetation Canopies.
An Automated Comparative Observation System for Sun-Induced Chlorophyll Fluorescence of Vegetation Canopies.
复制标题
植被冠层太阳诱导叶绿素荧光的自动比较观测系统
DOI：
10.3390/s16060775
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发表时间：
2016-05-27
期刊：
影响因子：
--
通讯作者：
Wu J
中科院分区：
文献类型：
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作者：
Zhou X;Liu Z;Xu S;Zhang W;Wu J
探测太阳诱导的叶绿素荧光（SIF）为遥感光合作用提供了新的途径。然而，要分析不同应力状态下SIF的响应特征，必须在冠层尺度上对不同应力状态下的植被进行长期时间序列对比观测，从而总结不同时间尺度下SIF变化规律的异同。本文设计了植被冠层SIF连续对比观测系统。该系统以高分辨率光谱仪和光复用器为基础，可实现多目标对比观测。为了同时测量O2-A和O2-B大气吸收波段的常用植被指数和SIF，采用了以下参数：光谱范围为475.9 ~ 862.2 nm，光谱分辨率约为0.9 nm，光谱采样间隔约为0.4 nm，信噪比（SNR）可高达1000:1。为了在较短的时间间隔内获得高信噪比的植被冠层向上辐射和向下辐射数据，提出了单步积分时间优化算法。为了优化SIF的提取精度，在该连续观测系统中，根据光谱分辨率、光谱采样间隔和光谱仪信噪比，使用FluorMOD模型对数据集进行模拟。利用这些数据集确定了弗劳恩霍夫线深度（FLD）、三FLD （3FLD）和光谱拟合方法（SFM）的最佳参数，并证实3FLD和SFM适合从光谱测量中提取SIF。利用该系统对甘薯和裸地的O2-A和O2-B吸收波段的SIF值以及一些常用植被指数进行了观测，结果表明：(1)甘薯叶片SIF值的日变化趋势与光合有效辐射（PAR）的日变化趋势基本一致；(2)裸地为非荧光发射器，其SIF显著小于甘薯；(3)基于实测数据的分析结果与基于模拟数据的分析结果基本一致。以上结果验证了从实测数据中提取的SIF的可靠性，以及利用该连续观测系统对比观测SIF值与常用的多植被冠层植被指数的可行性。该方法有利于全面分析植被冠层的应力响应特性。
Detecting sun-induced chlorophyll fluorescence (SIF) offers a new approach for remote sensing photosynthesis. However, to analyse the response characteristics of SIF under different stress states, a long-term time-series comparative observation of vegetation under different stress states must be carried out at the canopy scale, such that the similarities and differences in SIF change law can be summarized under different time scales. A continuous comparative observation system for vegetation canopy SIF is designed in this study. The system, which is based on a high-resolution spectrometer and an optical multiplexer, can achieve comparative observation of multiple targets. To simultaneously measure the commonly used vegetation index and SIF in the O2-A and O2-B atmospheric absorption bands, the following parameters are used: a spectral range of 475.9 to 862.2 nm, a spectral resolution of approximately 0.9 nm, a spectral sampling interval of approximately 0.4 nm, and the signal-to-noise ratio (SNR) can be as high as 1000:1. To obtain data for both the upward radiance of the vegetation canopy and downward irradiance data with a high SNR in relatively short time intervals, the single-step integration time optimization algorithm is proposed. To optimize the extraction accuracy of SIF, the FluorMOD model is used to simulate sets of data according to the spectral resolution, spectral sampling interval and SNR of the spectrometer in this continuous observation system. These data sets are used to determine the best parameters of Fraunhofer Line Depth (FLD), Three FLD (3FLD) and the spectral fitting method (SFM), and 3FLD and SFM are confirmed to be suitable for extracting SIF from the spectral measurements. This system has been used to observe the SIF values in O2-A and O2-B absorption bands and some commonly used vegetation index from sweet potato and bare land, the result of which shows: (1) the daily variation trend of SIF value of sweet potato leaves is basically same as that of photosynthetically active radiation (PAR); and (2) the bare land is a non-fluorescent emitter, the SIF of which is significantly smaller than that of sweet potato; and (3) analysis result based on the measured data is basically same as that based on simulated data. The above results verified the reliability of the SIF extracted from the measured data and the feasibility of comparatively observing the SIF value and the commonly used vegetation index of multiple vegetation canopy with this continuous observation system. This approach is beneficial for comprehensively analysing the stress response characteristics of vegetation canopies.