Satellite solar-induced chlorophyll fluorescence tracks physiological drought stress development during 2020 southwest US drought

Authors: ZHANG, Y. - Peking University; FANG, J. - Peking University; SMITH, W.K. - University Of Arizona; WANG, X. - University Of Arizona; GENTINE, P. - Columbia University; Scott, Russell - Russ; MIGLIAVACCA, M. - European Commission-Joint Research Centre (JRC); JEONG, S. - Seoul University; LITVAK, M. - University Of New Mexico; ZHOU, S. - Beijing Normal University

Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2023
Publication Date: 3/16/2023
Citation: Zhang, Y., Fang, J., Smith, W., Wang, X., Gentine, P., Scott, R.L., Migliavacca, M., Jeong, S., Litvak, M., Zhou, S. 2023. Satellite solar-induced chlorophyll fluorescence tracks physiological drought stress development during 2020 southwest US drought. Global Change Biology. 29(12):3395-3408. https://doi.org/10.1111/gcb.16683.
DOI: https://doi.org/10.1111/gcb.16683

Interpretive Summary: Determining drought impacts on plant growth from space remains a major challenge, with important implications for understanding plant mortality and predicting the climate change impacts on Earth’s carbon and water cycles. New measurements from space from the international space station (the Orbiting Carbon Observatory 3, or OCO-3) offer a new opportunity to track plant growth from space. We derived a new method to use these measurements to detect plant drought stress, which enabled us to map plant drought stress over large regions. The maps show good consistency with on the ground measurements of plant photosynthesis during the 2020 southwest US drought. Our findings highlight the potential of using these new, unique observations to advance the understanding of drought impacts on the Earth’s ecosystems.

Technical Abstract: Monitoring and estimating drought impacts on plant physiological processes at large scale remains a major challenge for remote sensing and land surface modeling, with important implications for understanding plant mortality mechanisms and predicting the climate change impact on terrestrial carbon and water cycles. Orbiting Carbon Observatory 3 (OCO-3), with its unique diurnal observing capability, offers a new opportunity to track drought stress on plant physiology. Using radiative transfer and machine learning modeling, we derive a metric of afternoon photosynthesis depression from OCO-3 solar-induced chlorophyll fluorescence (SIF) as an indicator of plant physiological drought stress. This unique signal offers spatially explicit mapping of plants’ responses to drought and shows good consistency with that derived from eddy covariance measurements during the 2020 southwest US drought. Although the spatial variation of the physiological drought stress is largely related to the vapor pressure deficit (VPD), plants’ sensitivity to VPD changes as the drought aggravates and exhibits a clear difference between shrubland and grassland. Our findings highlight the potential of using diurnal satellite SIF observations to advance the mechanistic understanding of drought impact on terrestrial ecosystems.