Remotely sensed plant fluorescence signals have the potential to facilitate a better understanding of vegetation photosynthetic dynamics. Space based observations of solar-induced chlorophyll fluorescence (SIF) provides an alternative non-invasive approach to investigate gross primary production (GPP), a key element of ecological research. Orbiting carbon observatory (OCO-2) is providing continuous global measurements of SIF at 757 nm and 771 nm wavelengths with nadir and glint mode observations. Using one of the three spectrometer instruments, measurements of SIF complements OCO-2’s Carbon dioxide data with information on when and where plants are drawing carbon from the atmosphere. Here, we present spatio-temporal patterns of space borne observations of SIF and its correlation with GPP and vegetation indices over diverse terrestrial vegetation of India. The results indicate a spatial variability in SIF ranging from 0.001 to 0.6 (± 0.16) Wm⁻² µm⁻¹ sr⁻¹ and 0.001 to 0.7 (± 0.2) Wm⁻² µm⁻¹ sr⁻¹ in nadir and glint modes, respectively. OCO-2 derived SIF at finer scale shows a similar trend with MODIS derived GPP during September–October–November and June–July–August seasons. A linear correlation of satellite derived SIF with GPP (Pearson’s coefficient, r = 0.84), EVI (r = 0.72) and NDVI (r = 0.63) at 757 nm for 0.05° × 0.05° grid over terrestrial India is reported, besides seasonal variations. Amongst the diverse vegetation types, SIF and GPP are well correlated over Evergreen broadleaf forests. The study provides new insights and useful inputs to GPP modelling and improved understanding of terrestrial carbon cycle research in India.

中文翻译：

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阐明印度陆地植被上太阳诱发的叶绿素荧光的空间观测

遥感植物荧光信号具有促进更好地了解植物光合作用动力学的潜力。对太阳诱导的叶绿素荧光（SIF）进行空间观测可提供一种替代性的非侵入性方法来研究初级总产值（GPP），这是生态研究的关键要素。轨道碳观测站（OCO-2）可以通过最低点和闪烁模式观测值连续提供757 nm和771 nm波长SIF的全局测量。使用这三种光谱仪中的一种，SIF的测量可以补充OCO-2的二氧化碳数据，并提供有关植物何时何地从大气中吸收碳的信息。这里，我们介绍了印度不同地面植被SIF的空间传播观测时空格局及其与GPP和植被指数的相关性。结果表明SIF的空间变化范围为0.001至0.6（±0.16）Wm在最低和闪烁模式下分别为^-2  µm ^-1  sr ^-1和0.001至0.7（±0.2）Wm ^-2  µm ^-1  sr ^-1。在9月-10月-11月和6月-7月-8月季节，OCO-2衍生的SIF规模较小，与MODIS衍生的GPP相似。据报道，除地面季节变化外，在印度陆上0.05°×0.05°网格上，卫星衍生的SIF与GPP（皮尔森系数，r = 0.84），EVI（r = 0.72）和NDVI（r = 0.63）在757 nm处的线性关系为757 nm。 。在多种植被类型中，SIF和GPP在常绿阔叶林上具有很好的相关性。这项研究为GPP建模提供了新的见识和有用的输入，并增进了对印度陆地碳循环研究的了解。