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    Author(s): Kurt H. JohnsenChris A. Maier; Lance W. Kress
    Date: 2005
    Source: Functional Ecology (2005) 19, 81–87
    Publication Series: Miscellaneous Publication
    PDF: View PDF  (294 KB)


    1. In order to help assess spatial competition for below-ground resources, we quantified the effects of fertilization on root biomass quantity and lateral root distribution of midrotation Pinus taeda trees. Open-top chambers exposed trees to ambient or ambient plus 200 µmol mol-1 atmospheric CO2 for 31 months.
    2. Tank CO2 was depleted in atmospheric 13C; foliage of elevated CO2 trees had δ13C of - 42·9%, compared with - 29·1% for ambient CO2 trees.
    3. Roots 1 m from the base of elevated CO2-grown trees had more negative δ13C relative to control trees, and this difference was detected, on average, up to 5·8, 3·7 and 3·7 m away from the trees for 0-2, 2-5 and >5 mm root-size classes, respectively. Non-fertilized tree roots extended as far as fertilized trees despite the fact that their above-ground biomass was less than half that of fertilized trees.
    4. These results are informative with respect to root sampling intensity and protocol, and the distances required between experimental manipulations to evaluate belowground processes of independent treatments.
    5. Fine-root turnover has usually been estimated to range from weeks to 3 years, representing a major avenue of carbon flux. Using a mixing model we calculated that 0-2 mm roots had a mean residence time of 4·5 years indicating relatively slow fineroot turnover, a result that has major implications in modelling C cycling.

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    Johnsen, Kurt H.; Maier, Chris A.; Kress, Lance W. 2005. Quantifying root lateral distribution and turnover using pine trees with a distinct stable carbon isotope signature. Functional Ecology (2005) 19, 81–87


    13C, carbon isotopes, carbon sequestration

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