# FluoC Spec 2--An Automated Field Spectroscopy System to Monitor Canopy Solar-Induced Fluorescence
## 4 Discussion
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Site Name** & **Location** & **Geolocation** & **Plant Functional Type** \\ \hline Pace & Virginia, USA & 37.9229, \(-\)78.2739 & Temperate mixed forest \\ Toolkit & Alaska, USA & 40.6223, \(-\)76.1222 & Tundra \\ MPJ & New Mexico, USA & 34.4385, \(-\)106.2377 & Pinon-Juniper \\ UIUC Energy Farm & Illinois, USA & 40.0658, \(-\)88.2084 & Crop (soybean) \\ Mead 1 & Nebraska, USA & 41.1649, \(-\)96.4701 & Crop (maize/soybean) \\ Mead 2 & Nebraska, USA & 41.1797, \(-\)96.4397 & Crop (maize/soybean) \\ Howland & Maine, USA & 45.2041, \(-\)68.7402 & Temperate evergreen forest \\ KAEFS * & Oklahoma, USA & 34.9846, \(-\)97.5223 & Grass (prairie; C3/C4) \\ Cheororon & Gangwon, Korea & 38.2013, 127.2506 & Crop (paddy rice) \\ CN-JRO ** & Jiangsu, China & 31.8068, 119.2173 & Crop (paddy rice) \\ CN-SHQ & Henan, China & 34.5203, 115.5894 & Crop (Wheat/Maize) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: SIF Network (FluoNET): site names, coordinates, and plant functional types (PFTs). * Kessler Atmospheric and Ecological Field Station ** Jurong Agricultural Ecosystem Station. and NPQ provide information on the stress-related changes in electron transport. Combining SIF, EC, and PRI measurements may help identify how the plant canopy as a whole uses absorbed photons. (2) GPP-SIF relationship across different biomes. FluoNet can help understand whether there is a biome-dependent relationship between SIF and GPP [58] or a universal GPP-SIF relationship globally [17]. More importantly, it can help us to understand the mechanism that drives this relationship, whether vegetation structure is the dominant control, what the time scale is, and whether the changes in the light use efficiency and yield of fluorescence (SIF\({}_{\text{yield}}\)) play important roles. (3) FluoNet can help us to understand the structural and biological controls of SIF signals. FluoNet aims to be inclusive and involve the efforts from groups that have designed other types of SIF systems. The overall goal is to enable an effective network to share ideas and data with the entire scientific community. A few existing and future satellite programs can be used to retrieve SIF, including GOSAT, GOME-2, OCO-2, OCO-3, TROPOMI, FLEX, and GeoCARB [8; 59; 60; 61]. Most of the satellites take a snapshot at a certain time of day (e.g., OCO-2 local time is around 1:30 p.m.), except GeoCARB, which is a geostationary satellite that can provide multiple observations in a day, and OCO-3, which will be installed on the International Space Station. Ground observations of SIF by FluoSpec 2 are thus instrumental to evaluate satellite SIF products [2]. FluoSpec 2 and similar sensors thus have their own niche by providing measurements at a high temporal frequency, which provide tools to study photosynthesis-related responses to plant stress [10; 62; 63; 64; 65]. FLUXNET, a global network of micrometeorological flux towers has opened a new era for ecosystem studies and has significantly contributed to scientific advancement in terrestrial ecology. We envision that a network of FluoSpec 2 and similar sensors could further move the ecosystem studies to the next stage. X.Y. designed the FluoSpec 2 system. X.Y., H.S., A.S. designed all the tests of FluoSpec 2 and installed three FluoSpec 2. All authors contributed to the improvement of FluoSpec 2 and the writing and editing of the manuscript. This work is supported by the startup funds from the University of Virginia for X.Y., installations of instruments are supported by the NASA Interdisciplinary Science (IDS) program (80 NSSC17K0110) and Brown University Institute at Brown for Environment and Society seed grant. YR's SIF system was supported by National Research Foundation of Korea (NRF-2016M1A3A3A02018195). Y.G.Z. is financially supported by the General Program of National Science Foundation of China (41671421).