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Biogeosciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/bg-2018-131
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
13 Apr 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).
Carbon Exchange in an Amazon Forest: from Hours to Years
Matthew N. Hayek1, Marcos Longo2, Jin Wu3, Marielle N. Smith4, Natalia Restrepo-Coupe5, Raphael Tapajós6, Rodrigo da Silva6, David R. Fitzjarrald7, Plinio B. Carmago8, Lucy R. Hutyra9, Luciana F. Alves10, Bruce Daube11, J. William Munger11, Kenia T. Wiedemann11, Scott R. Saleska12, and Steven C. Wofsy11 1Harvard Law School, Cambridge, MA, United States
2NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States
3Biological, Environmental & Climate Sciences Department, Brookhaven National Lab, Upton, New York, NY, United States
4Department of Forestry, Michigan State University, East Lansing, MI, United States
5Plant Functional Biology and Climate Change Cluster, University of Technology Sydney, Sydney, NSW, Australia
6Universidade Federal do Oeste do Pará, Santarém, PA, Brazil
7University at Albany SUNY, Albany, NY, United States
88 Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, Piracicaba, SP, Brazil
9Department of Earth and Environment, Boston University, Boston, MA
10Center for Tropical Research, Institute of the Environment and Sustainability, UCLA, Los Angeles, CA, United States
11Faculty of Arts and Sciences, Harvard University, Cambridge, MA, United States
12Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, United States
Abstract. 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, 0.59 respectively). Our model also simulated annual NEE well, with exception to 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. We did not find evidence to support the common assumption that droughts or disturbances affected this region during 2005 or 2010, nor that the forest phenology was seasonally light- or water-triggered. Our results suggest drought can have lasting impacts on photosynthesis, possibly via partial damage to still-living trees.
Citation: Hayek, M. N., Longo, M., Wu, J., Smith, M. N., Restrepo-Coupe, N., Tapajós, R., da Silva, R., Fitzjarrald, D. R., Carmago, P. B., Hutyra, L. R., Alves, L. F., Daube, B., Munger, J. W., Wiedemann, K. T., Saleska, S. R., and Wofsy, S. C.: Carbon Exchange in an Amazon Forest: from Hours to Years, Biogeosciences Discuss., https://doi.org/10.5194/bg-2018-131, in review, 2018.
Matthew N. Hayek et al.
Matthew N. Hayek et al.
Matthew N. Hayek et al.

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Short summary
Amazon rain forests sequester carbon dioxide, but they sequester or emit different amounts between years. We investigate these inter-annual differences using atmospheric measurements at our research site. We partition the roles that weather and forest disturbances like drought play. We discover that a simple model of weather can largely explain the differences between years, but a prior drought, which occurred 3 years before measurements started, likely hampered photosynthesis in the first year.
Amazon rain forests sequester carbon dioxide, but they sequester or emit different amounts...
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