Amazonian productivity to seasonal water stress: observations from GOSAT chlorophyll fluorescence

Jung-Eun Lee, Jet Propulsion Lab, jung-eun.lee@jpl.nasa.gov (Presenter)
Christian Frankenberg, Jet Propulsion Laboratory / Caltech, christian.frankenberg@jpl.nasa.gov
Christiaan van der Tol, University of Twente, tol@itc.nl
Joseph A Berry, Carnegie Institution for Science, joeberry@stanford.edu
Luis Guanter, Free University of Berlin, luis.guanter@wew.fu-berlin.de
C Kevin Boyce, University of Chicago, ckboyce@uchicago.edu
Joshua B Fisher, Jet Propulsion Lab, joshua.b.fisher@jpl.nasa.gov
Sassan Saatch, Jet Propulsion Lab, sasan.s.saatchi@jpl.nasa.gov

It is unclear to what extent seasonal water stress impacts plant productivity over Amazonia. Using new GOSAT satellite measurements of 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 QSCAT 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 (r2=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 (r2 = 0.79) was obtained using a fixed leaf area index, indicating that GPP changes are more related to environmental conditions than chlorophyll contents. We include in our analysis the extreme 2010 drought in Amazonia, which led to a 0.8 Pg C reduction (15% decrease from 2009) in basin-wide GPP when the dry season extends to drought.

Presentation Type:  Poster

Session:  Poster Session 2-B   (Wed 4:30 PM)

Associated Project(s): 

• Related Activity or Previously Funded TE Activity

Poster Location ID: 60