1. Agrosphere Institute (IBG-3); Forschungszentrum Jülich; 52425 Jülich Germany
2. Earth and Environmental Systems Institute, Pennsylvania State Univ.; University Park PA 16802
3. Géosciences Rennes; Univ. de Rennes; 35042 Rennes cedex France
4. Institute of Tibetan Plateau Research; Chinese Academy of Sciences; Beijing 100101 China
5. Geosciences and Natural Resource Management; Univ. of Copenhagen; DK-1350 Copenhagen Denmark