1. UMR 1391 ISPA, INRA, Bordeaux Sciences Agro; Villenave d'Ornon 33883 France
2. Forest & Nature Lab; Faculty of Bioscience Engineering, Ghent University; Geraardsbergse Steenweg 267 9090 Gontrode (Melle) Belgium
3. Department of Geosciences and Natural Resource Management; University of Copenhagen; Rolighedsvej 23 DK-1958 Frederiksberg C Denmark
4. Vantaa Research Department, Finnish Forest Research Institute; PO Box 18 FI-01301 Vantaa Finland
5. Department of Forest and Conservation Sciences, Faculty of Forestry; University of British Columbia; Vancouver British Columbia Canada
6. Biogéochimie des écosystèmes forestiers; INRA; Centre de Nancy 54280 Champenoux France