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Title: Drought impacts on photosynthesis, isoprene emission and atmospheric formaldehyde in a mid-latitude forest

Isoprene plays a critical role in air quality and climate. Photosynthesis (gross primary productivity, GPP) and formaldehyde (HCHO) are both related to isoprene emission at large spatiotemporal scales, but neither is a perfect proxy. Here we apply multiple satellite products and site-level measurements to examine the impact of water deficit on the three interlinked variables at the Missouri Ozarks site during a 20-day mild dryness stress in summer 2011 and a 3-month severe drought in summer 2012. Isoprene emission shows opposite responses to the short- and long-term droughts, while GPP was substantially reduced in both cases. In 2012, both remote-sensed solar-induced fluorescence (SIF) and satellite HCHO column qualitatively capture reductions in flux-derived GPP and isoprene emission, respectively, on weekly to monthly time scales, but with muted responses. For instance, as flux-derived GPP approaches zero in late summer 2012, SIF drops by 29–33% (July) and 19–27% (August) relative to year 2011. A possible explanation is that electron transport and photosystem activity are maintained to a certain extent under the drought stress. Similarly, flux tower isoprene emissions in July 2012 are 54% lower than July 2011, while the relative reductions in July for 3 independent satellite-derived HCHO data products are 27%, 12%more » and 6%, respectively. Finally, we attribute the muted HCHO response to a photochemical feedback whereby reduced isoprene emission increases the oxidation capacity available to generate HCHO from other volatile organic compound sources. Satellite SIF offers a potential alternative indirect method to monitor isoprene variability at large spatiotemporal scales from space, although further research is needed under different environmental conditions and regions. Our analysis indicates that fairly moderate reductions in satellite SIF and HCHO column may imply severe drought conditions at the surface.« less
ORCiD logo [1] ;  [2] ; ORCiD logo [3] ; ORCiD logo [4] ;  [4] ;  [5] ; ORCiD logo [6] ;  [7] ;  [3] ;  [3] ;  [4] ;  [8] ; ORCiD logo [9] ;  [10]
  1. Yale Univ., New Haven, CT (United States). Dept. of Geology and Geophysics
  2. Univ. of Exeter (United Kingdom). College of Engineering, Mathematics and Physical Sciences
  3. Carnegie Inst. for Science, Stanford, CA (United States). Dept. of Global Ecology
  4. Univ. of California, Irvine, CA (United States). Dept. of Earth System Science
  5. Univ. of Leicester (United Kingdom). Dept. of Physics and Astronomy, EOS Group
  6. DePaul Univ., Chicago, IL (United States). Environmental Science and Studies
  7. Univ. of Rochester, NY (United States). Dept. of Earth and Environmental Sciences
  8. Univ. of Innsbruck (Austria). Inst. of Atmospheric and Cryospheric Sciences
  9. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Sciences Division
  10. Univ. of Missouri, Columbia, MO (United States). Dept. of Forestry
Publication Date:
Grant/Contract Number:
AC05-00OR22725; NNX12AB90G; NNX13AC48G; 1342076
Accepted Manuscript
Journal Name:
Atmospheric Environment (1994)
Additional Journal Information:
Journal Name: Atmospheric Environment (1994); Journal Volume: 167; Journal Issue: C; Journal ID: ISSN 1352-2310
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); National Aeronautics and Space Administration (NASA); National Science Foundation (NSF)
Country of Publication:
United States
54 ENVIRONMENTAL SCIENCES; The Missouri Ozarks; Satellite; Formaldehyde; Gross primary productivity; Solar-induced fluorescence; Water stress
OSTI Identifier: