1. Dep. of Agroecology; Aarhus Univ.; Blichers Allé 20 DK-8830 Tjele Denmark
2. Dep. of Civil Engineering; Aalborg Univ.; Sofiendalsvej 9-11 DK-9200 Aalborg Denmark
3. Dep. of Soil, Water and Environmental Science; Univ. of Arizona; 1177 E. 4th Street Tucson AZ 85721