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Reconciling Carbon-cycle Concepts, Terminology, and Methods |
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| Authors: | F S Chapin III G M Woodwell J T Randerson E B Rastetter G M Lovett D D Baldocchi D A Clark M E Harmon D S Schimel R Valentini C Wirth J D Aber J J Cole M L Goulden J W Harden M Heimann R W Howarth P A Matson A D McGuire J M Melillo H A Mooney J C Neff R A Houghton M L Pace M G Ryan S W Running O E Sala W H Schlesinger E-D Schulze |
| Institution: | 1. Institute of Arctic Biology, University of Alaska–Fairbanks, Fairbanks, Alaska, 99775, USA 2. The Woods Hole Research Center, Woods Hole, Massachusetts, 02543, USA 3. Department of Earth System Science, University of California, Irvine, California, 92697, USA 4. The Ecosystem Center, Marine Biological Laboratory, Woods Hole, Massachusetts, 02543, USA 5. Institute of Ecosystem Studies, Millbrook, New York, 12545, USA 6. Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, 94720, USA 7. Department of Biology, University of Missouri, St. Louis, Missouri, 63121-4499, USA 8. Department of Forest Science, Oregon State University, Corvallis, Oregon, 97331-5752, USA 9. National Center for Atmospheric Research, Boulder, Colorado, 80305, USA 10. Department of Forest Science and Environment, University of Tuscia, I-01100, Viterbo, Italy 11. Max-Planck-Institute for Biogeochemistry, D-07701, Jena, Germany 12. Complex Systems Research Center, University of New Hampshire, Durham, New Hampshire, 03824, USA 13. US Geological Survey, Menlo Park, California, 94025, USA 14. Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York, 14853, USA 15. Department of Geological and Environmental Sciences, Stanford University, Stanford, California, 94305-2115, USA 16. US Geological Survey, Alaska Cooperative Fish and Wildlife Research Unit, University of Alaska–Fairbanks, Fairbanks, Alaska, 99775, USA 17. Department of Biological Sciences, Stanford University, Stanford, California, 94305-2115, USA 18. Geological Sciences and Environmental Studies, University of Colorado, Boulder, Colorado, 80309, USA 19. Rocky Mountain Research Station, USDA Forest Service, Fort Collins, Colorado, 80526-2098, USA 20. Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island, 02912, USA 21. Nicholas School of the Environment and Earth, Duke University, Durham, North Carolina, 27708-0329, USA |
| Abstract: | Recent projections of climatic change have focused a great deal of scientific and public attention on patterns of carbon (C) cycling as well as its controls, particularly the factors that determine whether an ecosystem is a net source or sink of atmospheric carbon dioxide (CO2). Net ecosystem production (NEP), a central concept in C-cycling research, has been used by scientists to represent two different concepts. We propose that NEP be restricted to just one of its two original definitions—the imbalance between gross primary production (GPP) and ecosystem respiration (ER). We further propose that a new term—net ecosystem carbon balance (NECB)—be applied to the net rate of C accumulation in (or loss from negative sign]) ecosystems. Net ecosystem carbon balance differs from NEP when C fluxes other than C fixation and respiration occur, or when inorganic C enters or leaves in dissolved form. These fluxes include the leaching loss or lateral transfer of C from the ecosystem; the emission of volatile organic C, methane, and carbon monoxide; and the release of soot and CO2 from fire. Carbon fluxes in addition to NEP are particularly important determinants of NECB over long time scales. However, even over short time scales, they are important in ecosystems such as streams, estuaries, wetlands, and cities. Recent technological advances have led to a diversity of approaches to the measurement of C fluxes at different temporal and spatial scales. These approaches frequently capture different components of NEP or NECB and can therefore be compared across scales only by carefully specifying the fluxes included in the measurements. By explicitly identifying the fluxes that comprise NECB and other components of the C cycle, such as net ecosystem exchange (NEE) and net biome production (NBP), we can provide a less ambiguous framework for understanding and communicating recent changes in the global C cycle. |
| Keywords: | net ecosystem production net ecosystem carbon balance gross primary production ecosystem respiration autotrophic respiration heterotrophic respiration net ecosystem exchange net biome production net primary production |
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