1. Dep. of Physical Geography; Utrecht Univ.; P.O. Box 80 115 3508 TC Utrecht the Netherlands
2. National Soil Resources Inst., Cranfield Univ.; North Wyke Research Station; Okehampton Devon EX20 2SB UK
3. British Geological Survey; Keyworth Nottingham NG12 5GG UK
4. Cross Institute Programme for Sustainable Soil Function, Institute of Grassland and Environmental Research (IGER); North Wyke Research Station; Okehampton Devon EX20 2SB UK
5. Dep. of Environmental Science; Lancaster Univ.; Lancaster LA1 4YQ UK