1. Graduate Group in Ecology Univ. of California Davis CA 95616
2. Instituto Nacional de Investigación Agropecuaria Treinta y Tres Uruguay
3. Univ. of California Coop., Ext. Oroville CA 95965
4. Dep. of Agronomy and Range Science and Dep. of Biological and Agricultural Engineering Univ. of California Davis CA 95616