## 1 Introduction
Using flux tower measurements, photosynthetic function is reliably estimated at the canopy level, and GPP can be estimated across the growing season at 30 min intervals. Both PAM fluorimetry and the eddy covariance approach are capable of accurately tracing the diurnal and seasonal dynamics in photosynthetic function, at leaf and canopy levels, respectively. However, both approaches lack the ability for spatial extrapolation beyond the sampled leaves or sites to the larger local and regional levels. Canopy SIF has been demonstrated to be useful for studying the temporal variability of photosynthesis in relationship to environmental constraints [26, 27, 28, 24]. Remote sensing of SIF is a research field of growing interest, with potential to provide an improved tool for monitoring plant status and photosynthetic function. Developments in airborne and space-borne remote sensing have provided opportunities to observe local, regional, and global terrestrial SIF patterns, and have attracted a considerable amount of attention within the scientific community [28, 29, 30, 31, 32, 33, 34, 35, 36, 37]. Recent technology developments have enabled the continuous diurnal and seasonal measurements of SIF at the leaf and canopy level [26, 28, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46] for extended periods, using automated very high resolution (\(\sim\)0.2 nm) spectral systems [47, 48, 49, 50]. Systems that are able to dynamically adjust the optimization settings with the changing light levels provide a consistent stream of comparable data capturing the SIF diurnal cycles throughout the growing season. At canopy level, the SIF signal has the potential to provide analogous information to the metrics obtained by light-adapted leaf F active PAM measurements, but cannot inform with regard to the dark-adapted metrics such as the non-photochemical quenching (NPQ) [47, 51]. The relationship of fluorescence with CO2 assimilation is highly dependent on the ambient PAR levels. In general, the operating efficiency of PSII is inversely associated with CO2 assimilation, and their correlation is stronger at higher PAR levels when photosynthesis is fully activated [17, 18, 19, 21]. There are essential differences between the leaf PAM F light-adapted and the canopy SIF methodologies, and, therefore, leaf and canopy level studies are needed that relate SIF measurements to photosynthetic performance, to characterize relationships between SIF and PAM F metrics [24, 47]. Further research is needed to characterize the effects of the diurnal and seasonal dynamics in environmental conditions on vegetation photosynthesis and the associated F and SIF properties, and to evaluate the ability of SIF metrics to characterize the diurnal and seasonal dynamics in photosynthesis. Further understanding of the mechanisms underlying the relationships of vegetation function and F, SIF, and reflectance VIs in different vegetation canopies and environments is essential for advancing their use in remote sensing, and will also contribute important understanding for ESA's forthcoming Fluorescence EXplorer (FLEX), Earth Explorer 8, which will measure reflectance and SIF together to assess seasonal photosynthetic patterns globally [29, 45, 52]. To advance the understanding of the utility of SIF metrics to monitor photosynthesis, our goal is to understand how the fine spatial and temporal scale red and far-red SIF (SIF\({}_{\text{B}}\) and SIF\({}_{\text{A}}\)) measurements relate to leaf-level F signals as well as to canopy VIs and GPP, or the carbon used by photosynthesis as measured by a flux tower, and therefore can be used for monitoring vegetation photosynthetic function. The objectives of this study are: to characterize the dynamic diurnal and seasonal relationships between canopy photosynthetic function and vegetation chlorophyll fluorescence and reflectance properties, at both leaf and canopy scales, and to evaluate the potential of SIF to scale leaf level F parameters to the canopy level for estimating GPP.