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This article in SSSAJ

  1. Vol. 63 No. 5, p. 1429-1435
    Received: Mar 4, 1998

    * Corresponding author(s): jandrews@ruf.rice.edu
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Separation of Root Respiration from Total Soil Respiration Using Carbon-13 Labeling during Free-Air Carbon Dioxide Enrichment (FACE)

  1. Jeffrey A. Andrews *a,
  2. Kevin G. Harrisonb,
  3. Roser Matamalac and
  4. William H. Schlesingerd
  1. a Dep. of Ecology & Evolutionary Biology—MS 170, Rice Univ., 6100 Main Street, Houston, TX 77005-1892 USA
    b Dep. of Geology and Geophysics, Boston College, Chestnut Hill, MA 02167 USA
    c Dep. of Botany, Duke Univ., Box 90340, Durham, NC 27708 USA
    d Dep. of Botany and Division of Earth and Ocean Sciences, Nicholas School of the Environment, Duke Univ., Box 90340, Durham, NC 27708 USA


Soil respiration constitutes a major component of the global carbon cycle and is likely to be altered by climatic change. However, there is an incomplete understanding of the extent to which various processes contribute to total soil respiration, especially the contributions of root and rhizosphere respiration. Here, using a stable carbon isotope tracer, we separate the relative contributions of root and soil heterotrophic respiration to total soil respiration in situ. The Free-Air Carbon dioxide Enrichment (FACE) facility in the Duke University Forest (NC) fumigates plots of an undisturbed loblolly pine (Pinus taeda L.) forest with CO2 that is strongly depleted in 13C. This labeled CO2 is found in the soil pore space through live root and mycorrhizal respiration and soil heterotroph respiration of labile root exudates. By measuring the depletion of 13CO2 in the soil system, we found that the rhizosphere contribution to soil CO2 reflected the distribution of fine roots in the soil and that late in the growing season roots contributed 55% of total soil respiration at the surface. This estimate may represent an upper limit on the contribution of roots to soil respiration because high atmospheric CO2 often increases in root density and/or root activity in the soil.

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