Solar-induced fluorescence (SIF) has shown great promise for probing spatiotemporal variations in terrestrial gross primary production (GPP), the largest component flux of the global carbon cycle. However, scale mismatches between SIF and ground-based GPP have posed challenges toward fully exploiting these data. We used SIF obtained at high spatial sampling rates and resolution by NASA's Orbiting Carbon Observatory-2 satellite to elucidate GPP-SIF relationships across space and time in the U.S. Corn Belt. Strong linear scaling functions (R2 ≥ 0.79) that were consistent across instantaneous to monthly time scales were obtained for corn ecosystems and for a heterogeneous landscape based on tall tower observations. Although the slope of the corn function was ~56% higher than for the landscape, SIF was similar for corn (C4) and soybean (C3). Taken together, there is strong observational evidence showing robust linear GPP-SIF scaling that is sensitive to plant physiology but insensitive to the spatial or temporal scale.
Bibliographical noteFunding Information:
The authors would like to acknowledge funding support provided by the United States Department of Agriculture (USDA-NIFA2013-67019-21364) and the Minnesota Corn Research and Promotion Council (4101-15SP). Funding for this AmeriFlux core site was provided by the U.S. Department of Energy's Office of Science. We are grateful to the University of Minnesota Supercomputing Institute for partial support of this work. J.D.W. acknowledges U.S. Department of Energy support for the University of Missouri (subcontract 4000150689). Corn GPP data are available from AmeriFlux (http://ameriflux.lbl.gov/), and tall tower data are archived at http://www.biometeorology.umn.edu/. The solar-induced fluorescence data (v. B7101r) were produced by the OCO-2 project at the Jet Propulsion Laboratory, California Institute of Technology, and obtained from the OCO-2 data archive maintained at the NASA Goddard Earth Science Data and Information Services Center. The MODIS FPAR/LAI (MCD15A2 v5), GPP (MYD17A2H v6), and EVI/NDVI (MYD13Q1 v5) were obtained from the Land Processes DAAC. The authors declare no conflict of interest.
©2016. American Geophysical Union. All Rights Reserved.
- eddy covariance
- tall tower fluxes