The key-role of topsoil moisture on CO2 efflux from a Mediterranean Quercus ilex forest Richard Joffre, Jean-Marc Ourcival, Serge Rambal and Alain Rocheteau Ann. For. Sci., 60 6 (2003) 519-526 Accepted: 01 June 2003 DOI: 10.1051/forest:2003045