1. Dep. of Agroecology and Environment, Faculty of Agricultural Sciences; Univ. of Aarhus; P.O. Box 50 DK-8830 Tjele Denmark
2. Dep. of Agricultural Sciences, Faculty of Life Science; Univ. of Copenhagen; Thorvaldsensvej 40 DK-1871 Frederiksberg C Denmark
3. Lehrstuhl für Bodenkunde; TU München; D-85350 Freising-Weihenstephan Germany
4. Dep. of Prehistoric Archaeology; Univ. of Aarhus; Moesgaard DK-8270 Højbjerg Denmark