Changes in the Demography of Plantago Coronopus at Two Coastal Sites

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Abstract
The demography of P. coronopus, a rosette-forming herb able to adopt an annual, biennial or short-lived perennial life cycle, was monitored at 2 coastal sites for 2 yr. Marked seasonal and between-year changes in seedling recruitment, mortality, population size and age-structure, and population density were documented. Individual rosette mortality was related to plant age and size. An exponential decay model (Deevey type II) gave a statistically significant fit for seedling cohorts, vegetatively-derived rosettes and population depletion curves. Half-lives of seedling cohorts ranged from 4.3 wk to 80.5 wk and decreased progressively during the study. Rossette mortality was density-dependent at both sites. Statistically significant relationships between plant mortality, cohort half-life, and prevailing population density were found. The role of density-dependent mortality and site disturbances in the maintainance of the populations is discussed.