Tropical rainforest carbon sink declines during El Niño as a result of reduced photosynthesis and increased respiration rates

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College of Forest Resources and Environmental Science


  • Changes in tropical forest carbon sink strength during El Niño Southern Oscillation (ENSO) events can indicate future behavior under climate change. Previous studies revealed ˜6 Mg C ha−1 yr−1 lower net ecosystem production (NEP) during ENSO year 1998 compared with non‐ENSO year 2000 in a Costa Rican tropical rainforest. We explored environmental drivers of this change and examined the contributions of ecosystem respiration (RE) and gross primary production (GPP) to this weakened carbon sink.
  • For 1998–2000, we estimated RE using chamber‐based respiration measurements, and we estimated GPP in two ways: using (1) the canopy process model MAESTRA, and (2) combined eddy covariance and chamber respiration data. MAESTRA‐estimated GPP did not statistically differ from GPP estimated using approach 2, but was ˜ 28% greater than published GPP estimates for the same site and years using eddy covariance data only.
  • A 7% increase in RE (primarily increased soil respiration) and a 10% reduction in GPP contributed equally to the difference in NEP between ENSO year 1998 and non‐ENSO year 2000.
  • A warming and drying climate for tropical forests may yield a weakened carbon sink from both decreased GPP and increased RE. Understanding physiological acclimation will be critical for the large carbon stores in these ecosystems.

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© 2017 The Authors. New Phytologist © 2017 New Phytologist Trust. Publisher’s version of record: https://doi.org/10.1111/nph.14724

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New Phytologist