ABSTRACT Spectroscopy plays a key role in Earth observations, especially for studies involving vegetation function and structure. These measurements are critical in the context of carbon cycle monitoring from leaf to global scales. Reflectance-based vegetation indices (RIs) have been used extensively in remote sensing studies from the unpiloted aerial vehicle, aerial, and space-based platforms to model quantities related to productivity, such as gross primary production (GPP), while more recently chlorophyll fluorescence (CF) measurements are increasingly exploited to track GPP. CF and RI measurements vary in magnitude, depend on different portions of the spectrum, and are derived from unique equations; thus, instrument uncertainty manifests distinctly for these measurements. Although this is well known, it is often unexamined in experiments and analyses. We use a portable spectroradiometer to make measurements of reflectance-based vegetation indices (RIs) and chlorophyll fluorescence (CF) in order to characterize how measurements of RIs and CF compare to one another. In particular, we examine fluorescence (F) and fluorescence yield (F Yield) under a light-emitting diode grow light (LED), solar-induced fluorescence (SIF), solar-induced fluorescence yield (SIFYield), absorbed photosynthetically active radiation (APAR), and reflectance-based vegetation indices (the normalized difference vegetation index (NDVI), the chlorophyll/carotenoid index (CCI), and the photochemical reflectance index (PRI)) and include maximized propagated uncertainty of the spectroradiometer for each measurement. We show that RIs have a significantly lower propagated error relative to the mean (0.01% to 0.28%) than CF measurements (0.01% to 1.28%) and that while fine resolution spectrometer CF measurements are outside the noise of the instrument and have potential to provide relative measurements of productivity, show why this instrument having fine spectral resolution and sampling is more effective for measurements of APAR and RIs. We also demonstrate that F and F Yield measurements have low propagated uncertainty and propose that future studies of plant function using this spectrometer/LED technique and the full range of spectra be undertaken. Finally, measurements of SIF, F, and APAR can provide estimates of SIFYieldand F Yield in the same order of magnitude, but further examination is required to determine how these measurements compare under a range of illumination and environmental conditions and how they might compare to PRI.

中文翻译：

---

叶绿素荧光的表征、吸收的光合有效辐射和基于反射的植被指数光谱辐射计测量

摘要 光谱学在地球观测中起着关键作用，特别是对于涉及植被功能和结构的研究。这些测量对于从叶到全球尺度的碳循环监测而言至关重要。基于反射率的植被指数 (RI) 已广泛用于无人驾驶飞行器、空中和天基平台的遥感研究，以模拟与生产力相关的数量，例如初级生产总值 (GPP)，而最近叶绿素荧光(CF) 测量越来越多地用于跟踪 GPP。CF 和 RI 测量值在幅度上有所不同，取决于频谱的不同部分，并且源自独特的方程；因此，对于这些测量，仪器的不确定性很明显。虽然这是众所周知的，它在实验和分析中常常未经检验。我们使用便携式光谱辐射计测量基于反射的植被指数 (RI) 和叶绿素荧光 (CF)，以表征 RI 和 CF 的测量结果如何相互比较。特别是，我们在发光二极管生长灯 (LED)、太阳诱导荧光 (SIF)、太阳诱导荧光产量 (SIFYield)、吸收的光合有效辐射下检查荧光 (F) 和荧光产率 (F Yield)（ APAR) 和基于反射的植被指数（归一化差异植被指数 (NDVI)、叶绿素/类胡萝卜素指数 (CCI) 和光化学反射指数 (PRI)），并包括光谱辐射计每次测量的最大传播不确定度。我们表明，与 CF 测量（0.01% 到 1.28%）相比，RI 相对于平均值（0.01% 到 0.28%）的传播误差要低得多，虽然高分辨率光谱仪 CF 测量在仪器噪声之外，并且有可能提供生产率的相对测量，说明为什么这种具有良好光谱分辨率和采样的仪器对于 APAR 和 RI 的测量更有效。我们还证明 F 和 F 产量测量具有低传播不确定性，并建议使用这种光谱仪/ LED 技术和全范围光谱进行植物功能的未来研究。最后，SIF、F 和 APAR 的测量值可以提供相同数量级的 SIFYield 和 F Yield 的估计值，