Carbon exchange in an Amazon forest: from hours to years

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  • Matthew N. Hayek
    Harvard Law School
  • Marcos Longo
    The California Institute of Technology
  • Jin Wu
    Brookhaven National Laboratory
  • Marielle Smith
    Michigan State University
  • Natalia Restrepo-Coupe
    University of Technology, Sydney
  • Raphael Tapajos
    Universidade Federal do Oeste do Pará
  • Rodrigo da Silva
    Universidade Federal do Oeste do Pará
  • David R. Fitzjarrald
    University at Albany, USA
  • Plinio B. Camargo
    Universidade de São Paulo
  • Lucy R. Hutyra
    Boston University
  • Luciana F. Alves
    University of California, Los Angeles
  • Bruce Daube
    Harvard University
  • J. William Munger
    Harvard University
  • Kenia T. Wiedemann
    Harvard University
  • Scott R. Saleska
    University of Arizona, Tucson
In Amazon forests, the relative contributions of climate, phenology, and disturbance to net ecosystem exchange of carbon (NEE) are not well understood. To partition influences across various timescales, we use a statistical model to represent eddy-covariance-derived NEE in an evergreen eastern Amazon forest as a constant response to changing meteorology and phenology throughout a decade. Our best fit model represented hourly NEE variations as changes due to sunlight, while seasonal variations arose from phenology influencing photosynthesis and from rainfall influencing ecosystem respiration, where phenology was asynchronous with dry-season onset. We compared annual model residuals with biometric forest surveys to estimate impacts of drought disturbance. We found that our simple model represented hourly and monthly variations in NEE well (R2=0.81 and 0.59, respectively). Modeled phenology explained 1 % of hourly and 26 % of monthly variations in observed NEE, whereas the remaining modeled variability was due to changes in meteorology. We did not find evidence to support the common assumption that the forest phenology was seasonally light- or water-triggered. Our model simulated annual NEE well, with the exception of 2002, the first year of our data record, which contained 1.2 MgC ha−1 of residual net emissions, because photosynthesis was anomalously low. Because a severe drought occurred in 1998, we hypothesized that this drought caused a persistent, multi-year depression of photosynthesis. Our results suggest drought can have lasting impacts on photosynthesis, possibly via partial damage to still-living trees.
Original languageEnglish
Pages (from-to)4833–4848
JournalBiogeosciences
Volume15
Issue number15
DOIs
Publication statusPublished - 15 Aug 2018
Externally publishedYes
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