, Volume 8, Issue 4, pp 412–429 | Cite as

Production of CO2 in Soil Profiles of a California Annual Grassland

  • Noah Fierer
  • Oliver A. Chadwick
  • Susan E. Trumbore
Original Articles


Soils play a key role in the global cycling of carbon (C), storing organic C, and releasing CO2 to the atmosphere. Although a large number of studies have focused on the CO2 flux at the soil–air interface, relatively few studies have examined the rates of CO2 production in individual layers of a soil profile. Deeper soil horizons often have high concentrations of CO2 in the soil air, but the sources of this CO2 and the spatiotemporal dynamics of CO2 production throughout the soil profile are poorly understood. We studied CO2 dynamics in six soil profiles arrayed across a grassland hillslope in coastal southern California. Gas probes were installed in each profile and gas samples were collected weekly or biweekly over a three-year period. Using soil air CO2 concentration data and a model based on Fick’s law of diffusion, we modeled the rates of CO2 production with soil profile depth. The CO2 diffusion constants were checked for accuracy using measured soil air 222Rn activities. The modeled net CO2 production rates were compared with CO2 fluxes measured at the soil surface. In general, the modeled and measured net CO2 fluxes were very similar although the model consistently underestimated CO2 production rates in the surficial soil horizons when the soils were moist. Profile CO2 production rates were strongly affected by the inter- and intra-annual variability in rainfall; rates were generally 2–10 times higher in the wet season (December to May) than in the dry season (June to November). The El Niño event of 1997–1998, which brought above-average levels of rainfall to the study site, significantly increased CO2 production in both the surface and subsurface soil horizons. Whole profile CO2 production rates were approximately three times higher during the El Niño year than in the following years of near-average rainfall. During the dry season, when the net rates of CO2 flux from the soil profiles are relatively low (4–11 mg C– CO2 m−2 h−1), 20%–50% of the CO2 diffusing out of the profiles appears to originate in the relatively moist soil subsurface (defined here as those horizons below 40 cm in depth). The natural abundance 14C signatures of the CO2 and soil organic C suggest that the subsurface CO2 is derived from the microbial mineralization of recent organic C, possibly dissolved organic C transported to the subsurface horizons during the wet season.


soil carbon soil respiration CO2 flux 14belowground processes vadose zone processes 


  1. Ajwa, HA, Rice, CW, Sotomayor, D 1998Carbon and nitrogen mineralization in tallgrass prairie and agricultural soil profilesSoil Sci Soc Am J6294251Google Scholar
  2. Amundson, R, Davidson, E 1990Carbon dioxide and nitrogenous gases in the soil atmosphereJ Geochem Explor381341CrossRefGoogle Scholar
  3. Amundson, R, Stern, L, Baisden, T, Wang, Y 1998The isotopic composition of soil and soil-respired CO2Geoderma8283114CrossRefGoogle Scholar
  4. Andrews, JA, Schlesinger, WH 2001Soil CO2 dynamics, acidification, and chemical weathering in a temperate forest with experimental CO2 enrichmentGlobal Biogeochem Cycles1514962CrossRefGoogle Scholar
  5. Batjes, NH 1996Total carbon and nitrogen in the soils of the worldEur J Soil Sci4715163CrossRefGoogle Scholar
  6. Billings, W 1995

    What we need to know: Some priorities for research on biotic feedbacks in a changing biosphere

    Woodwell, GMacKenzie, F eds. Biotic feedbacks in the global climatic system: will warming feed the warming?Oxford University PressNew York377392
    Google Scholar
  7. Billings, SA, Richter, DD, Yarie, J 1998Soil carbon dioxide fluxes and profile concentrations in two boreal forestsCan J For Res J28177383CrossRefGoogle Scholar
  8. Burton, DL, Beauchamp, EG 1994Profile nitrous oxide and carbon dioxide concentrations in a soil subject to freezingSoil Sci Soc Am J5811522Google Scholar
  9. Cerling, T, Solomon, D, Quade, J, Bowman, J 1991On the isotopic composition of carbon in soil carbon dioxideGeochim Cosmochim Acta5534045CrossRefGoogle Scholar
  10. Chamran, F, Gessler, P, Chadwick, O 2002Spatially explicit treatment of soil–water dynamics along a semiarid catenaSoil Sci Soc Am J66157183Google Scholar
  11. Chapin, F, Matson, P, Mooney, H 2002Principles of Terrestrial Ecosystem EcologySpringerNew YorkGoogle Scholar
  12. Collin, M, Rasmuson, A 1988A comparison of gas diffusivity models for unsaturated porous mediaSoil Sci Soc Am J52155965Google Scholar
  13. Davidson, EA, Trumbore, SE 1995Gas diffusivity and production of CO2 in deep soils of the eastern AmazonTellus Ser B Chem Phys Meteorol4755065CrossRefGoogle Scholar
  14. deJong, E, Schappert, H 1972Calculation of soil respiration and activity from CO2 profiles in the soilSoil Sci11332833Google Scholar
  15. Dibblee, T 1966Santa Ynez Mountains: Geology of the Central Santa Ynez Mountains Santa Barbara CountyCalifornia Division of Mines and Geology, Department of ConservationCaliforniaGoogle Scholar
  16. Dorr, H, Munnich, K 1990222Rn flux and soil air concentration profiles in West Germany. Soil 222Rn as tracer for gas transport in the unsaturated soil zoneTellus Ser B Chem Phys Meteorol42208CrossRefGoogle Scholar
  17. Ehleringer, JR, Buchmann, N, Flanagan, LB 2000Carbon isotope ratios in belowground carbon cycle processesEcol Appl1041222Google Scholar
  18. Elberling, B 2003Seasonal trends of soil CO2 dynamics in a soil subject to freezingJ Hydrol27615975CrossRefGoogle Scholar
  19. Eswaran, H, Berg, EVD, Reich, P 1993Organic carbon in soils of the worldSoil Sci Soc Am J571924Google Scholar
  20. Fierer, N, Schimel, J, Holden, P 2003Variations in microbial community composition through two soil depth profilesSoil Biol Biochem3516776CrossRefGoogle Scholar
  21. Gaudinski, JB, Trumbore, SE, Davidson, EA, Zheng, S 2000Soil carbon cycling in a temperate forest: Radiocarbon-based estimates of residence times, sequestration rates and partitioning of fluxesBiogeochemistry (Dordrecht)513369Google Scholar
  22. Gessler, PE, Chadwick, OA, Chamran, F, Althouse, L, Holmes, K 2000Modeling soil-landscape and ecosystem properties using terrain attributesSoil Sci Soc Am J64204656Google Scholar
  23. Hendry, M, Mendoza, C, Kirkland, R, Lawrence, J 1999Quantification of transient CO2 production in a sandy unsaturated zoneWater Resources Res35218998CrossRefGoogle Scholar
  24. Hillel D. 1998. Environmental Soil Physics. San Diego: Academic Press. Hooper B. 2003. Spatial and temporal analysis of moisture and temperature as controls on soil respiration at the hillslope scale in California oak savanna [M.S. dissertation]. University of California, Santa BarbaraGoogle Scholar
  25. Keller, CK, Bacon, D 1998Soil respiration and georespiration distinguished by transport analyses of vadose CO2, 13CO2, and 14CO2Global Biogeochem Cycles1236172CrossRefGoogle Scholar
  26. Khalil, M, Rasmussen, R, Shearer, M 1998Flux measurements and sampling strategies: Applications to methane emissions from rice fieldsJ Geophys Res103252119CrossRefGoogle Scholar
  27. Millington, R, Shearer, R 1971Diffusion in aggregated porous mediaSoil Sci1113728Google Scholar
  28. Nazaroff, W 1992Radon transport from soil to airRev Geophys3013760Google Scholar
  29. Pumpanen, J, Ilvesniemi, H, Hari, P 2003A process-based model for predicting soil carbon dioxide efflux and concentrationSoil Sci Soc Am J6740213Google Scholar
  30. Raich, JW, Schlesinger, WH 1992The global carbon dioxide flux in soil respiration and its relationship to vegetation and climateTellus Ser B Chem Phys Meteorol448199CrossRefGoogle Scholar
  31. Rambal, S, Debussche, G. 1995

    Water balance of Mediterranean ecosystems under a changing climate

    Moreno, JOechel, W eds. Global Change and Mediterranean-Type EcosystemsSpringer-VerlagNew York386407
    Google Scholar
  32. Richter, D, Markewitz, D 1995How deep is soil?Bioscience456009Google Scholar
  33. Rovira, P, Vallejo, VR 1997Organic carbon and nitrogen mineralization under Mediterranean climatic conditions: The effects of incubation depthSoil Biol Biochem29150920CrossRefGoogle Scholar
  34. Rustad, LE, Huntington, TG, Boone, RD 2000Controls on soil respiration: Implications for climate changeBiogeochem4816CrossRefGoogle Scholar
  35. Schimel, DS 1995Terrestrial ecosystems and the carbon cycleGlobal Change Biol17791Google Scholar
  36. Schimel, DS, Braswell, BH, Holland, EA, McKeown, R, Ojima, DS, Painter, TH, Parton, WJ, Townsend, AR 1994Climatic, edaphic, and biotic controls over storage and turnover of carbon in soilsGlobal Biogeochem Cycles827993CrossRefGoogle Scholar
  37. Schlesinger, W 1991 Biogeochemistry: An Analysis of Global ChangeAcademic PressNew YorkGoogle Scholar
  38. Shipman GE. 1972. Soil Survey of Santa Barbara County, USDA Soil Conservation Service.Google Scholar
  39. Soil Survey Staff1996aKeys to Soil Taxonomy7USDA-NRCSLincoln, NEGoogle Scholar
  40. Soil Survey Staff1996bSoil survey laboratory methods manual, version 3.0USDA-NRCSLincoln, NEGoogle Scholar
  41. Solomon, DK, Cerling, TE 1987The annual carbon dioxide cycle in a montane soil: observations, modeling, and implications for weatheringWater Resources Res23225765Google Scholar
  42. Stranden, E, Kolstad, A, Lind, B 1984The influence of moisture and temperature on radon exhalationRadiat Protect Dosim7558Google Scholar
  43. Stuiver, M, Polach, H 1977Reporting of 14C dataRadiocarbon1935563Google Scholar
  44. Stumm, W, Morgan, J 1981Aquatic Chemistry: An Introduction Emphasizing Chemical Equilibria in Natural Waters2John Wiley & SonsNew YorkGoogle Scholar
  45. Thorstenson, D, Pollock, D 1989Gas transport in unsaturated zones: Multicomponent systems and the adequacy of Fick’s lawWater Resources Res25477507Google Scholar
  46. Trumbore, S 2000Age of soil organic matter and soil respiration: Radiocarbon constraints on belowground C dynamicsEcol Appl10399411Google Scholar
  47. Vogel, J 1992A rapid method for preparation of biomedical targets for AMSRadiocarbon3434450Google Scholar
  48. Wood, W, Petraitis, M 1984Origin and distribution of carbon dioxide in the unsaturated zone of the southern high plains of TexasWater Resources Res201193 208Google Scholar
  49. Wood, B, Keller, C, Johnstone, D 1993In situ measurement of microbial activity and controls on microbial CO2 production in the unsaturated zoneWater Resources Res2964759CrossRefGoogle Scholar
  50. Yavitt, JB, Fahey, TJ, Simmons, JA 1995Methane and carbon dioxide dynamics in a northern hardwood ecosystemSoil Sci Soc Am J59796804Google Scholar
  51. Yoshikawa, S, Hasegawa, S 2000Diurnal and seasonal changes in CO2 concentration and flux in an Andisol and simulation based on changes in CO2 production rate and gas diffusivityJpn Agric Res34113Google Scholar

Copyright information

© Springer Science+Business Media, Inc. 2005

Authors and Affiliations

  • Noah Fierer
    • 1
  • Oliver A. Chadwick
    • 2
  • Susan E. Trumbore
    • 3
  1. 1.Department of BiologyDuke UniversityDurhamUSA
  2. 2.Department of GeographyUniversity of CaliforniaSanta BarbaraUSA
  3. 3.Department of Earth System ScienceUniversity of CaliforniaIrvineUSA

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