Abstract Solar-induced chlorophyll fluorescence (SIF) measured from space has been increasingly used to quantify plant photosynthesis at regional and global scales. Apparent canopy SIF yield (SIFyield apparent), determined by fluorescence yield (ΦF) and escaping ratio (fesc), together with absorbed photosynthetically active radiation (APAR), is crucial in driving spatio-temporal variability of SIF. While strong linkages between SIFyield apparent and plant physiological responses and canopy structure have been suggested, spatio-temporal variability of SIFyield apparent at regional scale remains largely unclear, which limits our understanding of the spatio-temporal variability of SIF and its relationship with photosynthesis. In this study, we utilized recent SIF data with high spatial resolution from two satellite instruments, OCO-2 and TROPOMI, together with multiple other datasets. We estimated SIFyield apparent across space, time, and different vegetation types in the U.S. Midwest during crop growing season (May to September) from 2015 to 2018. We found that SIFyield apparent of croplands was larger than non-croplands during peak season (July–August). However, SIFyield apparent between corn (C4 crop) and soybean (C3 crop) did not show a significant difference. SIFyield apparent of corn, soybean, forest, and grass/pasture show clear seasonal and spatial patterns. The spatial variability of precipitation during the growing season could explain the overall spatial pattern of SIFyield apparent. Further analysis by decomposing SIFyield apparent into ΦF and fesc using near-infrared reflectance of vegetation (NIRV) suggests that fesc may be the major driver of the observed variability of SIFyield apparent.

中文翻译：

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来自 OCO-2 和 TROPOMI 的卫星足迹数据揭示了美国中西部太阳诱导荧光产量的显着时空和植被间类型变异

摘要 从空间测量的太阳诱导叶绿素荧光 (SIF) 已越来越多地用于量化区域和全球范围内的植物光合作用。由荧光产量 (ΦF) 和逃逸率 (fesc) 以及吸收的光合有效辐射 (APAR) 决定的表观冠层 SIF 产量（SIFyield 表观）对于驱动 SIF 的时空变异性至关重要。虽然已经表明 SIF 产量表观和植物生理响应与冠层结构之间存在很强的联系，但 SIF 产量表观在区域尺度上的时空变异性仍然很大程度上不清楚，这限制了我们对 SIF 时空变异性及其与光合作用关系的理解。在这项研究中，我们利用了来自两个卫星仪器 OCO-2 和 TROPOMI 的具有高空间分辨率的最新 SIF 数据，与多个其他数据集一起。我们估算了 2015 年至 2018 年美国中西部作物生长季节（5 月至 9 月）跨空间、时间和不同植被类型的 SIFyield 表观。我们发现，在旺季（7 月至 9 月）农田的 SIFyield 表观大于非农田八月）。然而，玉米（C4 作物）和大豆（C3 作物）之间的 SIF 产量表观没有显示出显着差异。SIF 玉米、大豆、森林和草地/牧场的表观产量显示出明显的季节和空间格局。生长季降水的空间变异性可以解释 SIF 产量表观的整体空间格局。