Measuring the Glow of Plants From Below

The Science

In forests, fields and beyond, plants use sunlight and carbon (photosynthesis) to grow and thrive, but our understanding of the process on the global scale is limited. Scientists found a way to measure the gross primary production using satellites and the faint red light given off by plant leaves. A satellite known as Orbiting Carbon Observatory-2 monitored that light and provided detailed information. The team’s approach was consistent with similar data from ground measurements and the observed area’s gross primary production.

The Impact

Photosynthesis is the foundation of life and civilization on Earth. Yet our current ability to measure photosynthesis at large scales is extremely limited. The team shows that solar-induced fluorescence (the red glow from plant leaves) is a direct proxy of photosynthesis and the relationship is likely consistent across biomes. This research opens up a new direction for photosynthesis observations at multiple scales. It also shows how ground-based observations can be integrated with satellite data to advance insights at local, regional, and global scales. 

Summary

Quantifying gross primary production (GPP) remains a major challenge in global carbon cycle research. Space-borne monitoring of solar-induced chlorophyll fluorescence, an integrative photosynthetic signal of molecular origin, can assist in terrestrial GPP monitoring. However, the extent to which SIF tracks spatiotemporal variations in GPP remains unresolved. Orbiting Carbon Observatory-2 (OCO-2)’s solar-induced fluorescence data acquisition and fine spatial resolution permit direct validation against ground and airborne observations. Empirical orthogonal function analysis shows consistent spatiotemporal correspondence between OCO-2 solar-induced fluorescence and GPP globally. A linear relationship between production and fluorescence is also obtained at eddy-flux sites covering diverse biomes, setting the stage for future investigations of the robustness of such a relationship across more biomes. The research team’s findings support the central importance of high-quality satellite fluorescence for studying terrestrial carbon cycle dynamics.

Funding

This research was supported by the National Aeronautics and Space Administration (NASA), the Biological and Environmental Research program in Department of Energy’s Office of Science, the Academy of Finland, the European Union, and Oak Ridge National Laboratory.

Publication

Y. Sun, C. Frankenberg, J.D. Wood, D.S. Schimel, M. Jung, L. Guanter, D.T. Drewry, M. Verma, A. Porcar-Castell, T.J. Griffis, L. Gu, T.S. Magney, P. Köhler, B. Evans, and K. Yuen, “OCO-2 advances photosynthesis observation from space via solar-induced chlorophyll fluorescence.” Science 358, 189 (2017). [DOI: 10.1126/science.aam5747]