1. Research Scientist, Civil and Environmental Engineering, Univ. of California Davis, One Shields Ave., Davis, CA 95616 (corresponding author).
2. Research Fellow, World Agroforestry Centre, ICRAF House, United Nations Ave., Gigiri, Nairobi, Kenya.
3. Professor, Dept. of Agricultural and Resource Economics, Univ. of California Davis, One Shields Ave., Davis, CA 95616.
4. Professor, Dept. of Land, Air and Water Resources, Univ. of California Davis, One Shields Ave., Davis, CA 95616.
5. Assistant Professor, Dept. of Agricultural and Resource Economics, Univ. of California Davis, One Shields Ave., Davis, CA 95616.
6. Junior Specialist, Dept. of Land, Air and Water Resources, Univ. of California Davis, One Shields Ave., Davis, CA 95616.
7. Soils Specialist, Univ. of California Cooperative Extension, One Shields Ave., Davis, CA 95616.
8. Professor, Civil and Environmental Engineering, Univ. of California, Davis, One Shields Ave., Davis CA 95616.