Isoprene emission rates and fluxes measured above a Mediterranean oak (Quercus pubescens) forest

The present work, carried out as part of the European fiEld experiments to COnstrain Models of atmospheric Pollution and Transport of Emissions project (ESCOMPTE), brings a new contribution to the inventory of the main natural hydrocarbons sources that are liable to participate in the production of ozone. The measurement campaign was conducted in Montmeyan, a site close to Marseilles (France), with the aim of quantifying the terpenic emission pattern and the behaviour of Quercus pubescens, an important Mediterranean tree species. Biogenic emissions by Q. pubescens were determined by the enclosure of an intact branch of this tree in a Teflon cuvette. The total monoterpenic emission rates thus recorded were found to reach maximum values ranged between 40 and 350 mug g(Dry Weight)(-1) h(-1). Emissions were correlated strongly with leaf temperature and Photosynthetic Active Radiation (PAR). The fluxes were also determined by extrapolating the results of the enclosure method and by using aerodynamic gradient method. They reach around 73 mg m(-2) h(-1) with the first method and 55 mg m(-2) h(-1) with the second one. The obtained values fit with a maximal ratio of 2. (C) 2004 Elsevier B.V. All rights reserved.