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Respiration response of mature sweetgum stems to carbon dioxide enrichment.
Edwards, Nelson1, 1
ABSTRACT- This research is a part of a Free-Air Carbon Dioxide Enrichment (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 near zero during 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. Most, of the increased respiration was due to increased stem growth. However, the enriched plot rates continued to be slightly higher than the control plot rates even during the dormant season when no growth was occurring.
KEY WORDS: Liquidambar styraciflua, stem respiration, carbon dioxide enrichment