Changes in the Demography of Plantago Coronopus at Two Coastal Sites

Abstract

(1) The demography of Plantago coronopus, a rosette-forming herb able to adopt an annual, biennial or short-lived perennial life cycle, was monitored at two coastal sites for 2 years. (2) 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. (3) An exponential decay model (Deevey type II) gave a statistically significant fit for seedling cohorts, vegetatively-derived rosettes and population depletion curves. (4) Half-lives of seedling cohorts ranged from 4-3 weeks to 80.5 weeks and decreased progressively during the study. (5) Rosette 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 maintenance of the populations is discussed.