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Proc Biol Sci. 2013 May 1;280(1761):20130171. doi: 10.1098/rspb.2013.0171. Print 2013 Jun 22.

Forest productivity and water stress in Amazonia: observations from GOSAT chlorophyll fluorescence.

Author information

  • 1Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA. jung-eun.lee@jpl.nasa.gov

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.

KEYWORDS:

Amazon; chlorophyll fluorescence; drought; water stress

PMID:
23760636
PMCID:
PMC3652436
DOI:
10.1098/rspb.2013.0171
[PubMed - indexed for MEDLINE]
Free PMC Article
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