Leaf isoprene emission rate as a function of atmospheric CO₂ concentration

• Published in: Global change biology Vol. 15; no. 5; pp. 1189 - 1200
• Main Authors: Wilkinson, Michael J, Monson, Russell K, Trahan, Nicole, Lee, Stanfield, Brown, Erin, Jackson, Robert B, Polley, H. Wayne, Fay, Philip A, Fall, Ray
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01-05-2009; Blackwell Publishing Ltd; Wiley-Blackwell
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; atmospheric chemistry; Biological and medical sciences; Carbon dioxide; CH; CH4; chemical concentration; Climate change; Climatology. Bioclimatology. Climate change; continuous gradient; Earth, ocean, space; Eucalyptus globulus; Exact sciences and technology; External geophysics; forests; Fundamental and applied biological sciences. Psychology; gas emissions; General aspects; global change; isoprenoids; leaves; Liquidambar styraciflua; Meteorology; methane; ozone; Paleoecology; Plant populations; Populus deltoides; Populus tremuloides; Trees; volatile organic compounds; Modification; Forests; O3; Emission; Ozone; Plant leaf; CH4; Dynamical climatology; Concentration measurement; Climate change; atmospheric chemistry; Atmosphere; Global change; Planetary scale
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/j.1365-2486.2008.01803.x

There is considerable interest in modeling isoprene emissions from terrestrial vegetation, because these emissions exert a principal control over the oxidative capacity of the troposphere. We used a unique field experiment that employs a continuous gradient in CO₂ concentration from 240 to 520 ppmv to demonstrate that isoprene emissions in Eucalyptus globulus were enhanced at the lowest CO₂ concentration, which was similar to the estimated CO₂ concentrations during the last Glacial Maximum, compared with 380 ppmv, the current CO₂ concentration. Leaves of Liquidambar styraciflua did not show an increase in isoprene emission at the lowest CO₂ concentration. However, isoprene emission rates from both species were lower for trees grown at 520 ppmv CO₂ compared with trees grown at 380 ppmv CO₂. When grown in environmentally controlled chambers, trees of Populus deltoides and Populus tremuloides exhibited a 30-40% reduction in isoprene emission rate when grown at 800 ppmv CO₂, compared with 400 ppmv CO₂. P. tremuloides exhibited a 33% reduction when grown at 1200 ppmv CO₂, compared with 600 ppmv CO₂. We used current models of leaf isoprene emission to demonstrate that significant errors occur if the CO₂ inhibition of isoprene is not taken into account. In order to alleviate these errors, we present a new model of isoprene emission that describes its response to changes in atmospheric CO₂ concentration. The model logic is based on assumed competition between cytosolic and chloroplastic processes for pyruvate, one of the principal substrates of isoprene biosynthesis.