Forest productivity and water stress in Amazonia: observations from GOSAT chlorophyll fluorescence
Abstract
It is unclear to what extent seasonal water stress impacts on plant productivity over Amazonia. Using new Greenhouse gases Observing SATellite (GOSAT) satellite measurements of sun-induced chlorophyll fluorescence, we show that midday fluorescence varies with water availability, both of which decrease in the dry season over Amazonian regions with substantial dry season length, suggesting a parallel decrease in gross primary production (GPP). Using additional SeaWinds Scatterometer onboard QuikSCAT satellite measurements of canopy water content, we found a concomitant decrease in daily storage of canopy water content within branches and leaves during the dry season, supporting our conclusion. A large part (r^2 = 0.75) of the variance in observed monthly midday fluorescence from GOSAT is explained by water stress over moderately stressed evergreen forests over Amazonia, which is reproduced by model simulations that include a full physiological representation of photosynthesis and fluorescence. The strong relationship between GOSAT and model fluorescence (r^2 = 0.79) was obtained using a fixed leaf area index, indicating that GPP changes are more related to environmental conditions than chlorophyll contents. When the dry season extended to drought in 2010 over Amazonia, midday basin-wide GPP was reduced by 15 per cent compared with 2009.
Additional Information
© 2013 The Author(s) Published by the Royal Society. Received: 24 January 2013. Accepted: 4 April 2013. We acknowledge the entire GOSAT team for having designed and built the instrument and especially A. Kuze and H. Suto for their tremendous efforts in helping understand GOSAT calibration in the O2 A-band. We acknowledge all MODIS land product science team members for providing an invaluable public dataset. ECMWF ERA-Interim data used in this study have been provided by ECMWF. We thank M. Zhao (University of Montana) for providing the updated LAI and GPP products and M. Jung and M. Reichstein for providing the MPI-BGC dataset. We also thank anonymous reviewers and S. Saleska for providing careful and constructive comments on our manuscript. L.G.'s work has been funded by the Emmy Noether Programme of the German Research Foundation (GlobFluo project), and S.S. acknowledges the support by Carbon Cycle funding from NASA under terrestrial ecology. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration, and is supported in part by the W.M. Keck Institute for Space Studies.Additional details
- Eprint ID
- 64615
- Resolver ID
- CaltechAUTHORS:20160219-153636924
- Deutsche Forschungsgemeinschaft (DFG)
- NASA
- Keck Institute for Space Studies (KISS)
- NASA/JPL/Caltech
- Created
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2016-02-20Created from EPrint's datestamp field
- Updated
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2021-11-10Created from EPrint's last_modified field
- Caltech groups
- Keck Institute for Space Studies, Division of Geological and Planetary Sciences