Affiliation: | 1. Department of Earth Sciences , University of Aarhus , Ny Munkegade, Building 520, DK-8000 , Aarhus C , Denmark;2. Department of Agroecology , Danish Institute of Agricultural Sciences , P. O. Box 50, DK-8830 , Tjele , Denmark E-mail: MogensH.Greve@agrsci.dk |