Department of Agro-Eenvironmental Science, Obihiro University of Agriculture and Veterinary Medicine, 11 block, Nishi 2 sen, Inada-cho, Obihiro, Hokkaido, 080-8555, Japan.
Research Faculty of Agriculture, Hokkaido University, Kita 9, Nishi 9, Kita-ku, Sapporo, Hokkaido, 060-8589, Japan.
J Plant Res. 2021 Jul;134(4):713-728. doi: 10.1007/s10265-021-01322-3. Epub 2021 Jun 22.
Solar-induced chlorophyll fluorescence (SIF) emissions were estimated by the "area-ratio Fraunhofer line depth (aFLD) method", a new retrieval methodology in spectra from a low spectral resolution (SR) spectroradiometer (MS-700: full width half maximum (FWHM) of 10 nm and spectral sampling interval of 3.3 nm), assisted with a scaling to reference SIF detected from high SR spectrum. The sparse pixels of a spectrum of low SR misses detecting the minimum of the OA absorption band around at 760 nm, which makes the SIF detection by conventional FLD methods lose accuracy considerably. To overcome this, the aFLD method uses the definite integral of spectra over a wide interval between 750 and 780 nm. The integration of the spectrum is insusceptible to the change in shape of the depression curve, leading to higher accuracy of the aFLD method. Daily SIF, calculated by the aFLD method using the spectra obtained with MS-700, was scaled to reference daily SIF calculated by the spectral fitting method using the spectra obtained from August to December 2019 with an ultrafine SR spectroradiometer (QE Pro, FWHM = 0.24 nm). As a result, SIF calculated from MS-700 spectra by aFLD method was strongly correlated with the reference SIF from QE Pro spectra (r = 0.81) and was successfully scaled. Then, the scaled 11-year SIF from MS-700 at a deciduous broadleaf forest showed the correlation with GPP at multiple time steps: daily, monthly, and yearly, consistently during 2008-2018. The comparison of aFLD-derived SIF with the global Orbiting Carbon Observatory-2 (OCO-2) SIF data set (GOSIF) showed high correlation on monthly values during 2008-2017 (r = 0.85). The combining approach of the aFLD method with a scaling to reference SIF successfully detected long-term canopy SIF emissions, which has great potential to provide essential information on ecosystem-level photosynthesis.
利用“面积比夫琅和费线深度（aFLD）方法”估算了太阳诱导叶绿素荧光（SIF）发射，这是一种新的从低光谱分辨率（SR）分光辐射计（MS-700：半最大值全宽（FWHM）为 10nm，光谱采样间隔为 3.3nm）获得的光谱中进行反演的方法，该方法借助于对从高 SR 光谱中检测到的参考 SIF 进行缩放来实现。低 SR 光谱中的稀疏像素会错过对 760nm 左右的 OA 吸收带的最小值的检测，这使得常规 FLD 方法的 SIF 检测准确性大大降低。为了克服这一问题，aFLD 方法使用了在 750nm 和 780nm 之间的宽间隔内对光谱进行积分的方法。光谱积分不受凹陷曲线形状变化的影响，因此 aFLD 方法的精度更高。利用 MS-700 获得的光谱，通过 aFLD 方法计算得到的每日 SIF 被缩放为 2019 年 8 月至 12 月利用超精细 SR 分光辐射计（QE Pro，FWHM=0.24nm）进行光谱拟合法计算得到的参考每日 SIF。结果表明，利用 aFLD 方法从 MS-700 光谱计算得到的 SIF 与利用 QE Pro 光谱计算得到的参考 SIF 具有很强的相关性（r=0.81），并且成功进行了缩放。然后，在落叶阔叶林，利用 MS-700 在 11 年内计算的 SIF 与 2008-2018 年期间的多个时间步的 GPP 具有相关性：日、月和年。利用 aFLD 方法得到的 SIF 与全球轨道碳观测站-2（OCO-2）SIF 数据集（GOSIF）进行比较，2008-2017 年月值相关性很高（r=0.85）。利用参考 SIF 对 aFLD 方法进行缩放的组合方法成功检测到了长期冠层 SIF 发射，这为提供生态系统水平光合作用的必要信息具有很大的潜力。
