LIFE-HISTORY AND POPULATION-DYNAMICS OF HORDEUM-JUBATUM ALONG A SOIL-SALINITY GRADIENT

This study examined the importance of the timing of germination and of seedling survival in determining the distribution of Hordeum jubatum along a soil salinity gradient. Survival and reproduction of mature plants were also observed over a 3-year period. Field observations indicated that seedling survival did not limit the distribution of H. jubatum except under unusually dry conditions. Seedling were long-lived and persisted at salinities unfavorable for growth and reproduction. The two germination cohorts of H. jubatum are important in maintaining populations in the unpredictable environment of inland salt marshes. Salinity stress increased over the study period because of abnormally dry conditions and resulted in a shift in the distribution of H. jubatum along a topographic gradient. There was greater seed production per inflorescence with an increase in soil salinity. At different points along the salinity gradient, H. jubatum behaved as an annual, a short-lived perennial, and a long-lived perennial.