Simulation of carbon cycling, including dissolved organic carbon transport, in forest soil locally enriched with 14C

E. Tipping, P. M. Chamberlain, M. Fröberg, P. J. Hanson, P. M. Jardine

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Abstract

The DyDOC model was used to simulate the soil carbon cycle of a deciduous forest at the Oak Ridge Reservation (Tennessee, USA). The model application relied on extensive data from the Enriched Background Isotope Study (EBIS), which exploited a short-term local atmospheric enrichment of radiocarbon to establish a large-scale manipulation experiment with different inputs of 14C from both above-ground and below-ground litter. The model was first fitted to hydrological data, then observed pools and fluxes of carbon and 14C data were used to fit parameters describing metabolic transformations of soil organic matter (SOM) components and the transport and sorption of dissolved organic matter (DOM). This produced a detailed quantitative description of soil C cycling in the three horizons (O, A, B) of the soil profile. According to the parameterised model, SOM turnover within the thin O-horizon rapidly produces DOM (46 gC m -2 a -1), which is predominantly hydrophobic. This DOM is nearly all adsorbed in the A- and B-horizons, and while most is mineralised relatively quickly, 11 gC m -2 a -1 undergoes a "maturing" reaction, producing mineral-associated stable SOM pools with mean residence times of 100-200 years. Only a small flux (~1 gC m -2 a -1) of hydrophilic DOM leaves the B-horizon. The SOM not associated with mineral matter is assumed to be derived from root litter, and turns over quite quickly (mean residence time 20-30 years). Although DyDOC was successfully fitted to C pools, annual fluxes and 14C data, it accounted less well for short-term variations in DOC concentrations.

Original languageEnglish
Pages (from-to)91-107
Number of pages17
JournalBiogeochemistry
Volume108
Issue number1-3
DOIs
StatePublished - Apr 2012

Funding

Acknowledgments The authors appreciate the EBIS field data collections effort of Donald E. Todd Jr., and detailed and time consuming 14C-analyses of Chris Swanston that made this paper possible. The work of E. Tipping and P.M. Chamberlain was supported by grant NE/D00697 from the UK Natural Environment Research Council. Associated support for the EBIS project for the efforts of M. Fröberg, P. J. Hanson and P. M. Jardine was provided by the U.S. Department of Energy, Office of Science, Biological and Environmental Research. Oak Ridge National Laboratory is managed by UT-Battelle, LLC for the U.S. Department of Energy under Contract No. DE-AC05-00OR22725. We are grateful to three anonymous referees for their constructive criticisms of the original submission, attention to which substantially improved the paper.

Keywords

  • C
  • Carbon
  • Cycling
  • Dissolved organic carbon
  • Dissolved organic matter
  • DyDOC model
  • Enriched Background Isotope Study
  • Litter manipulation
  • Soil

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