Germination, Recruitment and Survival in the Weedy Annual Medicago polymorpha in Successive Wet and Dry Years

Abstract

-Germination, establishment and survival in Medicago polymorpha, a weedy winter annual, were studied during 2 successive seasons in California. Seeds were dormant when produced in spring and remained largely dormant following exposure to summer conditions. Approximately 40% of viable seeds in the seed bank were carried over from year to year. Consequently, autumn recruitment of seedlings is due in large part to germination of seeds produced in previous years. Seedling emergence was mostly simultaneous following the first substantial autumn rains. Survival to reproduction differed between years; few individuals produced seeds prior to senescence in the dry year, whereas in the wet year most overwintering individuals successfully produced fruits.