, Volume 77, Issue 1, pp 91-116

First online:

Long-term Effects of Free Air CO2 Enrichment (FACE) on Soil Respiration

  • E. S. BernhardtAffiliated withDepartment of Biology, LSRC B234, Duke University Email author 
  • , J. J. BarberAffiliated withDepartment of Mathematical Sciences, Montana State University
  • , J. S. PippenAffiliated withNicholas School of the Environment and Earth Sciences, Duke University
  • , L. TanevaAffiliated withDepartment of Biological Sciences, University of Illinois at Chicago
  • , J. A. AndrewsAffiliated withLocke, Liddell & Sapp
  • , W. H. SchlesingerAffiliated withNicholas School of the Environment and Earth Sciences, Duke University

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Emissions of CO2 from soils make up one of the largest fluxes in the global C cycle, thus small changes in soil respiration may have large impacts on global C cycling. Anthropogenic additions of CO2 to the atmosphere are expected to alter soil carbon cycling, an important component of the global carbon budget. As part of the Duke Forest Free-Air CO2 Enrichment (FACE) experiment, we examined how forest growth at elevated (+200 ppmv) atmospheric CO2 concentration affects soil CO2 dynamics over 7 years of continuous enrichment. Soil respiration, soil CO2 concentrations, and the isotopic signature of soil CO2 were measured monthly throughout the 7 years of treatment. Estimated annual rates of soil CO2 efflux have been significantly higher in the elevated plots in every year of the study, but over the last 5 years the magnitude of the CO2 enrichment effect on soil CO2 efflux has declined. Gas well samples indicate that over 7 years fumigation has led to sustained increases in soil CO2 concentrations and depletion in the δ 13C of soil CO2 at all but the shallowest soil depths.


Carbon dioxide enrichment Del 13C Duke Forest FACE Soil CO2 Soil respiration