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Journal of Environmental Quality Abstract -

Soil Carbon Dynamics beneath Switchgrass as Indicated by Stable Isotope Analysis


This article in JEQ

  1. Vol. 29 No. 2, p. 645-653
    Received: May 14, 1999

    * Corresponding author(s): ctg@ornl.gov
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  1. C. T. Garten Jr. * and
  2. S. D. Wullschleger
  1. Environmental Sciences Division, Oak Ridge National Lab., P.O. Box 2008, Oak Ridge, TN 37831-6038.



Surface (0–40 cm) soil organic carbon (SOC) dynamics were studied beneath four switchgrass (Panicum virgatum L.) field trials in the southeastern United States. Soil organic carbon was partitioned into particulate organic matter (POM) and mineral-associated organic matter (MOM). Most (75–90%) of the SOC at each study site was affiliated with MOM (<0.053 mm). Changes in stable carbon isotope ratios were used to derive carbon inputs to and losses from POM and MOM at each site. Inventories of existing SOC and new C4-derived SOC beneath switchgrass decreased with increasing soil depth. Approximately 5 yr after establishment, 19 to 31% of the existing SOC inventories beneath switchgrass had been derived from new C4-carbon inputs. Calculated turnover times of POM and MOM ranged from 2.4 to 4.3 yr and 26 to 40 yr, respectively. The turnover time of SOC in the POM fraction increased with decreasing mean annual temperature. A simple, two-compartment model was parameterized to predict the potential for soil carbon sequestration under switchgrass. An example calculation with the model indicated a measurable and verifiable recovery of soil carbon (≈12% increase) on degraded lands through one decade of switchgrass production. The potential to sequester carbon through switchgrass cultivation will depend on initial soil carbon inventories, prevailing climate, soil type, and site management.

Research sponsored by the Biofuels System Division, U.S. Department of Energy under contract No. DE-AC05-96OR22464 with Lockheed Martin Energy Research Corporation. Publication No. 4926, Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831.

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