@article{1edb2724f32f4c83bfbd9f754362693d,
title = "Spatially-explicit monitoring of crop photosynthetic capacity through the use of space-based chlorophyll fluorescence data",
abstract = "Plant functional traits such as photosynthetic capacity are critical parameters for terrestrial biosphere models. However, their spatial and temporal characteristics are still poorly represented. In this study, we used satellite observations of sun-induced fluorescence (SIF) to estimate top-of-canopy photosynthetic capacity (maximum carboxylation rate, Vcmax at a reference temperature of 25 °C) for crops, which was in turn utilized to simulate regional gross primary production (GPP). We first estimate the key parameter, Vcmax, in the widely-used FvCB photosynthesis model using field measurements of CO2 and water fluxes during 2007–2012 at seven crop eddy covariance flux sites over the US Corn Belt. The results showed that satellite far-red SIF retrievals have a stronger link to Vcmax at the seasonal scale (R2 = 0.70 for C4 and R2 = 0.63 for C3 crop) as compared with widely-used vegetation indices. We calibrate an empirical model linking Vcmax with SIF that was used to estimate spatially and temporally varying crop Vcmax for the US Corn Belt region. The resulting Vcmax maps are used together with meteorological data from MERRA reanalysis data and vegetation structural parameters derived from the satellite-based spectral reflectance data to constrain the Soil-Canopy Observation of Photosynthesis and Energy (SCOPE) balance model in order to estimate regional crop GPP. Our results show a substantial improvement in the seasonal and spatial patterns of cropland GPP when compared with crop yield inventory data. The evaluation with tall tower atmospheric CO2 measurements further supports our estimation of spatiotemporal Vcmax from space-borne SIF. Considering that SIF has a direct link to photosynthetic activity, our findings highlight the potential to infer regional Vcmax using remotely sensed SIF data and to use this information for a better quantification of regional cropland carbon cycles.",
keywords = "Chlorophyll fluorescence, Cropland, Leaf maximum carboxylation rate (V), Regional GPP, SCOPE, Sun-induced",
author = "Yongguang Zhang and Luis Guanter and Joanna Joiner and Lian Song and Kaiyu Guan",
note = "This research by Y.Z. is financially supported by the National Key R&D Program of China ( 2016YFA0600202 ), General Program of National Science Foundation of China ( 41671421 ), the International Cooperation and Exchange Programs of National Science Foundation of China (Sino-German, 41761134082 ), Jiangsu Provincial Natural Science Foundation for Distinguished Young Scholars of China ( BK20170018 ), and the Key Research Program of the Chinese Academy of Sciences (Grant NO., KFZD-SW-310 ). The study is also partially funded by Scientific Research Satellite Engineering of Civil Space Infrastructure Project (Forestry products and its practical techniques research on Terrestrial Ecosystem Carbon Inventory Satellite, 2016K-10). LG is supported by the Emmy Noether Programme (GlobFluo project, GU 1276/1-1 ) of the German Research Foundation . JJ is supported by funding from the NASA Earth Science US Participating Investigator program. MODIS MOD13 EVI/NDVI data were obtained from the MODIS LP DAAC archive and MERIS-MTCI from the Infoterra Ltd server. This work used eddy covariance data acquired by the AmeriFlux. We further thank the PIs of the flux tower sites: J. H., Prueger (USBr1, National Laboratory for Agriculture and the Environment), A. Suyker (USNe1-3, Univ. Nebraska). This research by Y.Z. is financially supported by the National Key R&D Program of China (2016YFA0600202), General Program of National Science Foundation of China (41671421), the International Cooperation and Exchange Programs of National Science Foundation of China (Sino-German, 41761134082), Jiangsu Provincial Natural Science Foundation for Distinguished Young Scholars of China (BK20170018), and the Key Research Program of the Chinese Academy of Sciences (Grant NO., KFZD-SW-310). The study is also partially funded by Scientific Research Satellite Engineering of Civil Space Infrastructure Project (Forestry products and its practical techniques research on Terrestrial Ecosystem Carbon Inventory Satellite, 2016K-10). LG is supported by the Emmy Noether Programme (GlobFluo project, GU 1276/1-1) of the German Research Foundation. JJ is supported by funding from the NASA Earth Science US Participating Investigator program. MODIS MOD13 EVI/NDVI data were obtained from the MODIS LP DAAC archive and MERIS-MTCI from the Infoterra Ltd server. This work used eddy covariance data acquired by the AmeriFlux. We further thank the PIs of the flux tower sites: J. H., Prueger (USBr1, National Laboratory for Agriculture and the Environment), A. Suyker (USNe1-3, Univ. Nebraska).",
year = "2018",
month = jun,
day = "1",
doi = "10.1016/j.rse.2018.03.031",
language = "English (US)",
volume = "210",
pages = "362--374",
journal = "Remote Sensing of Environment",
issn = "0034-4257",
publisher = "Elsevier Inc.",
}