A New Way to Measure Photosynthesis

ecological gradients

The marked ecological gradients depicted by OCO-2’s high-resolution SIF measurements along a transect of temperate deciduous forests, crops, and urban area from Indiana to suburban Chicago, Illinois.

Weather-related stresses like the heat and drought affect plant growth around the globe, but understanding the impact on a regional or global scale is a challenge. Most estimates of plant productivity are based on satellite data examining greenness, but plants remain green even when heat has shut down photosynthesis for the day or longer.

Thanks to new technology from NASA combined with research from the University of Minnesota, scientists have a new way to measure the plant canopy for productivity. This study was recently published in Science. Instead of greenness, the NASA satellite OCO-2 measures a process that occurs only during photosynthesis, called solar-induced chlorophyll fluorescence (SIF). Plants take in more solar energy during photosynthesis than they need to grow, and they release a small portion of the excess energy back to the atmosphere in the form of fluorescent light. SIF has been measured before by satellite, but OCO-2 measurements are higher in resolution than any previous dataset.

Sun Ying of Cornell University, formerly a NASA Jet Propulsion Laboratory postdoctoral scholar and colleagues report on the first validation of OCO-2's SIF measurements using ground and airborne observations of plant photosynthesis and growth. They found a close agreement between the satellite and measurements collected by Tim Griffis, John Baker and the Biometeorology Group at the University of Minnesota, suggesting that OCO-2's SIF capability will be a powerful tool for understanding the health of plants globally.

This new, better way to measure the plant canopy productivity will be useful for agricultural measurement, tracking droughts and better understanding vegetation’s role in our climate.

The Biometeorology Group is part of the Department of Soil, Water, and Climate at the College of Food, Agricultural, and Natural Resources. Its mission is to advance the understanding of Earth system processes and the interaction among land, atmosphere and water and improve people’s lives and our world through teaching, research, and extension.

Full paper:
"OCO-2 advances photosynthesis observation from space via solar-induced chlorophyll fluorescence", 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 (Science, 2017, 358 (6360), eaam5747, doi: 10.1126/science.aam5747)

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