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Assessing net ecosystem carbon exchange of U.S. terrestrial ecosystems by integrating eddy covariance flux measurements and satellite observations |
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| Institution: | a Department of Earth & Atmospheric Sciences, Purdue Climate Change Research Center, Purdue University, West Lafayette, IN 47907, USA b Department of Earth & Atmospheric Sciences, Department of Agronomy, Purdue Climate Change Research Center, Purdue University, West Lafayette, IN 47907, USA c College of Forestry, Oregon State University, Corvallis, OR 97331, USA d Ecosystem Science Division, Department of Environmental Science, Policy and Management, University of California, Berkeley, CA 94720, USA e Department of Environmental Sciences, University of Toledo, Toledo, OH 43606, USA f Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA g Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA, USA h Department of Meteorology, Pennsylvania State University, University Park, PA 16802, USA i USDA Forest Service, Northeastern Research Station, Durham, NH 03824, USA j Department of Land, Air and Water Resources, University of California, Davis, CA 95616, USA k Nicholas School of the Environment, Duke University, Durham, NC 27708, USA l Department of Forestry and Environmental Resources and Southern Global Change Program, North Carolina State University, Raleigh, NC 27695, USA m Lawrence Berkeley National Laboratory, Environmental Energy Technologies Division, Atmospheric Science Department, Berkeley, CA 94720, USA n School of Natural Resources, University of Nebraska-Lincoln, Lincoln, NE 68583, USA o Argonne National Laboratory, Environmental Science Division, Argonne, IL 60439, USA p USDA Forest Service, Southern Research Station, Raleigh, NC 27606, USA q Division of Engineering and Applied Science/Department of Earth and Planetary Science, Harvard University, Cambridge, MA 02138, USA r Department of Forest Resources, University of Minnesota, St. Paul, MN 55108, USA s Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309, USA t Department of Evolution, Ecology, and Organismal Biology, Ohio State University, Columbus, OH 43210, USA u Smithsonian Environmental Research Center, Edgewater, MD 21037, USA v Harvard Forest and Department of Organismic and Evolutionary Biology, Harvard University, Petersham, MA 01366, USA w Oak Ridge National Laboratory Environmental Sciences Division, Oak Ridge, TN 37831, USA x Harvard Forest, Harvard University, Petersham, MA 01366, USA y Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA z School of Forest Resources & Conservation, University of Florida, Gainesville, FL 32611, USA aa Argonne National Laboratory, Biosciences Division, Argonne, IL 60439, USA bb NOAA/ARL, Atmospheric Turbulence and Diffusion Division, Oak Ridge, TN 37831, USA cc Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA dd Department of Biology, San Diego State University, San Diego, CA 92182, USA ee Department of Geography, Indiana University, Bloomington, IN 47405, USA ff Atmospheric Environmental Research, Institute of Meteorology and Climate Research, Research Center Karlsruhe (FZK/IMK-IFU), Kreuzeckbahnstr, 19, 82467 Garmisch-Partenkirchen, Germany gg USDA-ARS Southwest Watershed Research Center, Tucson, AZ 85719, USA hh Department of Biological Sciences, University of Alabama, Tuscaloosa, AL 35487, USA ii Lawrence Berkeley National Laboratory, Earth Science Division, Berkeley, CA 94720, USA |
| Abstract: | More accurate projections of future carbon dioxide concentrations in the atmosphere and associated climate change depend on improved scientific understanding of the terrestrial carbon cycle. Despite the consensus that U.S. terrestrial ecosystems provide a carbon sink, the size, distribution, and interannual variability of this sink remain uncertain. Here we report a terrestrial carbon sink in the conterminous U.S. at 0.63 pg C yr−1 with the majority of the sink in regions dominated by evergreen and deciduous forests and savannas. This estimate is based on our continuous estimates of net ecosystem carbon exchange (NEE) with high spatial (1 km) and temporal (8-day) resolutions derived from NEE measurements from eddy covariance flux towers and wall-to-wall satellite observations from Moderate Resolution Imaging Spectroradiometer (MODIS). We find that the U.S. terrestrial ecosystems could offset a maximum of 40% of the fossil-fuel carbon emissions. Our results show that the U.S. terrestrial carbon sink varied between 0.51 and 0.70 pg C yr−1 over the period 2001-2006. The dominant sources of interannual variation of the carbon sink included extreme climate events and disturbances. Droughts in 2002 and 2006 reduced the U.S. carbon sink by ∼20% relative to a normal year. Disturbances including wildfires and hurricanes reduced carbon uptake or resulted in carbon release at regional scales. Our results provide an alternative, independent, and novel constraint to the U.S. terrestrial carbon sink. |
| Keywords: | Net ecosystem carbon exchange Eddy covariance MODIS Carbon sink U S Interannual variability Drought Disturbance |
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