, Volume 9, Issue 7, pp 1041-1050

First online:

Reconciling Carbon-cycle Concepts, Terminology, and Methods

  • F. S. ChapinIIIAffiliated withInstitute of Arctic Biology, University of Alaska–Fairbanks Email author 
  • , G. M. WoodwellAffiliated withThe Woods Hole Research Center
  • , J. T. RandersonAffiliated withDepartment of Earth System Science, University of California
  • , E. B. RastetterAffiliated withThe Ecosystem Center, Marine Biological Laboratory
  • , G. M. LovettAffiliated withInstitute of Ecosystem Studies
  • , D. D. BaldocchiAffiliated withDepartment of Environmental Science, Policy, and Management, University of California
  • , D. A. ClarkAffiliated withDepartment of Biology, University of Missouri
  • , M. E. HarmonAffiliated withDepartment of Forest Science, Oregon State University
  • , D. S. SchimelAffiliated withNational Center for Atmospheric Research
    • , R. ValentiniAffiliated withDepartment of Forest Science and Environment, University of Tuscia
    • , C. WirthAffiliated withMax-Planck-Institute for Biogeochemistry
    • , J. D. AberAffiliated withComplex Systems Research Center, University of New Hampshire
    • , J. J. ColeAffiliated withInstitute of Ecosystem Studies
    • , M. L. GouldenAffiliated withDepartment of Earth System Science, University of California
    • , J. W. HardenAffiliated withUS Geological Survey
    • , M. HeimannAffiliated withMax-Planck-Institute for Biogeochemistry
    • , R. W. HowarthAffiliated withDepartment of Ecology and Evolutionary Biology, Cornell University
    • , P. A. MatsonAffiliated withDepartment of Geological and Environmental Sciences, Stanford University
    • , A. D. McGuireAffiliated withUS Geological Survey, Alaska Cooperative Fish and Wildlife Research Unit, University of Alaska–Fairbanks
    • , J. M. MelilloAffiliated withThe Ecosystem Center, Marine Biological Laboratory
    • , H. A. MooneyAffiliated withDepartment of Biological Sciences, Stanford University
    • , J. C. NeffAffiliated withGeological Sciences and Environmental Studies, University of Colorado
    • , R. A. HoughtonAffiliated withThe Woods Hole Research Center
    • , M. L. PaceAffiliated withInstitute of Ecosystem Studies
    • , M. G. RyanAffiliated withGeological Sciences and Environmental Studies, University of Colorado
    • , S. W. RunningAffiliated withRocky Mountain Research Station, USDA Forest Service
    • , O. E. SalaAffiliated withDepartment of Ecology and Evolutionary Biology, Brown University
    • , W. H. SchlesingerAffiliated withNicholas School of the Environment and Earth, Duke University
    • , E.-D. SchulzeAffiliated withMax-Planck-Institute for Biogeochemistry

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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.


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