Stem respiration increases in CO2-enriched sweetgum trees

Authors

  • Nelson T. Edwards,

    Corresponding author
    1. Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6422, USA
      Author for correspondence:
      Nelson T. Edwards
      Tel.: +1 865 576 4868
      Fax: +1 865 576 9939
      Email: nte@ornl.gov
    Search for more papers by this author
  • Timothy J. Tschaplinski,

    1. Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6422, USA
    Search for more papers by this author
  • Richard J. Norby

    1. Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6422, USA
    Search for more papers by this author

Author for correspondence:
Nelson T. Edwards
Tel.: +1 865 576 4868
Fax: +1 865 576 9939
Email: nte@ornl.gov

Summary

  • • Stem respiration in trees results in substantial CO 2 release to the atmosphere. Stem respiration is an important component of the carbon budget of forest stands that could be perturbed by CO 2 enrichment of the atmosphere.
  • • We measured stem respiration in a free-air CO 2 enrichment (FACE) experiment in a 15-yr-old sweetgum ( Liquidambar styraciflua ) plantation. The trees were exposed to ambient or 1.4× ambient [CO 2 ]. Stem respiration of 12 trees in ambient [CO 2 ] and 12 trees in CO 2 -enriched plots was continuously monitored over a period of 1 year.
  • • CO2 enrichment caused a 23% increase in annual growth respiration (Rg) and a 48% increase in maintenance respiration (Rm). During a 4-d period when CO2 fumigation was turned off, both respiration and stem sucrose concentrations declined in the CO2-enriched trees. Concentrations of other soluble sugars did not change.
  • • We conclude that elevated [CO 2 ] caused stem respiration to increase and that the increase was driven by increased substrate supply from leaves. We suggest that both Rg and Rm rate responses may result from changes in growth rates and live to dead tissue ratios rather than from mechanistic alterations of the respiratory processes.

Ancillary