Abstract, Ecological Society of America Annual Meeting, Madison, WI, August, 2001

EDWARDS, NT. Oak Ridge National Laboratory, Oak Ridge, TN 37831-6422. Respiration response of mature sweetgum stems to CO₂ enrichment.

This research is a part of a Free-Air Carbon Dioxide Experiment (FACE) in a 15-year-old sweetgum (Liquidambar styraciflua) plantation in eastern Tennessee. The trees are exposed to ambient or 1.4X ambient CO₂ concentrations during the growing season. The objective of this project was to evaluate the effect of CO₂ enrichment on stem respiration. Stem respiration was measured by infrared analysis of CO₂ concentrations in the air stream pumped through chambers attached to tree stems. An automated system permitted the continuous monitoring of stem respiration rates of 32 trees (eight in each of two CO₂ enriched plots and eight in each of two control plots). Respiration rates in all tree stems followed a diurnal pattern with rates lagging slightly behind changes in stem temperature. Rates were higher in trees growing in CO₂ enriched plots than in controls. Differences varied with season of the year from zero throughout the dormant season to 100% during parts of the growing season (typically about 30%). Some trends toward higher Q₁₀ responses were also observed under CO₂ enrichment. Some, if not all, of the increased respiration was due to increased stem growth.