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Proc Natl Acad Sci U S A. 2019 Jun 11;116(24):11640-11645. doi: 10.1073/pnas.1900278116. Epub 2019 May 28.

Mechanistic evidence for tracking the seasonality of photosynthesis with solar-induced fluorescence.

Author information

Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125;
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109.
School of Biological Sciences, University of Utah, Salt Lake City, UT 84112.
Department of Biology, Bowdoin College, Brunswick, ME 04287.
Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA 90095.
Department of Geography, University of Colorado, Boulder, CO 80309.
Mesoscale and Microscale Meteorology Laboratory, National Center for Atmospheric Research, Boulder, CO 80301.
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125.


Northern hemisphere evergreen forests assimilate a significant fraction of global atmospheric CO2 but monitoring large-scale changes in gross primary production (GPP) in these systems is challenging. Recent advances in remote sensing allow the detection of solar-induced chlorophyll fluorescence (SIF) emission from vegetation, which has been empirically linked to GPP at large spatial scales. This is particularly important in evergreen forests, where traditional remote-sensing techniques and terrestrial biosphere models fail to reproduce the seasonality of GPP. Here, we examined the mechanistic relationship between SIF retrieved from a canopy spectrometer system and GPP at a winter-dormant conifer forest, which has little seasonal variation in canopy structure, needle chlorophyll content, and absorbed light. Both SIF and GPP track each other in a consistent, dynamic fashion in response to environmental conditions. SIF and GPP are well correlated (R 2 = 0.62-0.92) with an invariant slope over hourly to weekly timescales. Large seasonal variations in SIF yield capture changes in photoprotective pigments and photosystem II operating efficiency associated with winter acclimation, highlighting its unique ability to precisely track the seasonality of photosynthesis. Our results underscore the potential of new satellite-based SIF products (TROPOMI, OCO-2) as proxies for the timing and magnitude of GPP in evergreen forests at an unprecedented spatiotemporal resolution.


evergreen forest; gross primary production (GPP); photosynthesis; remote sensing; solar-induced fluorescence (SIF)

[Available on 2019-11-28]

Conflict of interest statement

The authors declare no conflict of interest.

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