First Year Seedling Survival of Jojoba (Simmondsia chinensis) in the Tucson Mountains, Arizona

Two-hundred and nineteen recently germinated jojoba seedlings were located in October and November 1974 and observed monthly for 12 months thereafter. Total seedling survival was 12%. Seedlings in a protected situation (associated with adult jojoba shrubs, other woody perennials, or rocks) had a significantly higher survival rate (22%), by December 1975, than seedlings growing in exposed sites (6%). Seedling mortality appeared to be related to both climatic (drought and freezing) and biotic (rodent) factors. Periods of vegetative growth and seedling germination were noted. Seedling establishment (germination plus seedling survival) of perennial is difficult in the Sonoran Desert. This is probably attributable to temporal variability of harsh climatic conditions, especially just above and below the soil surface, and biotic factors. The first 12 months of seedling life are particularly critical to seedling establishment (Shreve 1911, 1917). Until we have a much better understanding of seedling establishment patterns in desert perennial plants, it will remain difficult to interpret the evolutionary significance of their life history phenomena. Jojoba, Simmondsia chinensis [Link] Schneider, is a dioecious evergreen perennial shrub widely distributed in the Sonoran Desert (Gentry 1958; Sherbrooke and Haase 1974). This study of seedling establishment success, conducted under natural conditions during a 12month period following germination, was undertaken to determine the rate of jojoba seedling survival, factors contributing to seedling mortality, and time of germination and seedling growth. Of particular concern was an evaluation of the hypothesis that jojoba seedlings germinating under shrubs and trees, or associated with shading rocks, have a higher survival rate than seedlings germinating in more exposed sites. Several investigators have found that saguaro seedlings (Cereus giganteus Engelm.) may depend on association with nurse plants