1. Belowground Ecosystem Group, Department of Forest Sciences; University of British Columbia; 2424 Main Mall Vancouver B.C. Canada V6T 1Z4
2. National School of Forestry; University of Cumbria; Penrith CA11 0AH UK
3. Departmento de Ecología y Biología Animal; Universidad de Vigo; 36310 Vigo Spain
4. Centre for Ecology and Hydrology; Lancaster Environment Centre; Library Avenue, Bailrigg Lancaster LA1 4AP UK