PARENT SESSION
Oral Session # 64: Plant Ecology V: Physiology and Function II.
Presiding: G North
Thursday, August 7. 8:00 AM to 11:30 AM, SITCC Meeting Room 102.

How will leaf respiration respond to growth under elevated [CO₂] in three diverse tree canopies?

Leakey, Andrew^*,1, Davey, Phillip², Allen, Damian³, Rogers, Alistair⁴, DeLucia, Evan¹, Drake, Bert⁵, Murthy, Ramesh⁶, Long, Steve¹, ¹ University of Illinois, Urbana, IL² University of Essex, Colchester, Essex, UK³ BASF Plant Science, Research Triangle Park, NC⁴ Brookhaven National Laboratory, Upton, NY⁵ Smithsonian Environmental Research Center, Edgewater, MD⁶ Columbia University Biosphere 2, Oracle, AZ

ABSTRACT- Terrestrial plant respiration is a large component of the global carbon cycle, releasing 10 times more carbon per annum than fossil fuel combustion. Some previous studies have shown an inhibition of leaf mitochondrial respiration under future elevated [CO₂] (-18 %), which would be sufficient to increase sequestration of carbon into biomass and partially offset rising atmospheric [CO₂]. However, the nature of the direct and indirect responses of respiration to growth at elevated CO₂ remains contentious. We used high-resolution differential oxygen analysis to assess respiration without the potential experimental artifacts arising from traditional infra-red gas analysis of CO₂ flux. We present data on the following diverse experimental forest canopies that have developed under elevated CO₂ in the field: Pinus taeda at FACTS-1, Duke Forest, NC; Populus deltoides at Biosphere 2, AZ; and Quercus myrtifolia & Quercus geminata at the Smithsonian open-top chamber facility, FL. We found: (A) no direct effect of elevated [CO₂] on respiration in any species at any time, but; (B) variation between 0 - 23 % greater respiration after long-term growth at elevated [CO₂]. Further data is presented assessing rates of respiration in canopies grown at elevated [CO₂] in relation to leaf photosynthetic, carbohydrate and nitrogen status.

Key words: Respiration, Elevated CO₂, Tree, Climate Change