1. State Key Lab. of Resources and Environmental Information Systems; Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences; Beijing 100101 China
2. Dep. of Geography; Univ. of Wisconsin; Madison WI 53706
3. Graduate Univ., Chinese Academy of Sciences; Beijing 100049 China
4. Key Lab. of Oasis Ecology and Desert Environment; Xinjiang Inst. of Ecology and Geography, Chinese Academy of Sciences; Urumqi Xinjiang 830011 China
5. Institute of Soil and Fertilizer, Xinjiang Academy of Agric. Sciences; Urumqi Xinjiang 830000 China
6. Dep. of Geology and Meteorology; Kean Univ.; Union NJ 07083