Population Growth Rates and Age Versus Stage-Distribution Models for Teasel (Dipsacus Sylvestris Huds.)

Mathematical models are developed to examine the population—level response of an herbaceous plant species (teasel, Dipsacus sylvestris Huds.) which was experimentally introduced into several habitats and monitored for 5 yr. Models based on morphological stages (size) rather than chronological age give more satisfactory results. Populations growth rates (λm) range from 0.63 to 2.60, which are likely typical for fugitive plants. Values are interpreted as responses to both external and internal factors. Grass litter, and the presence of other dicotyledonous species, and the overall primary productivity of the rest of the community are important factors determining the success or failure of an attempted colonization by teasel. Individual plant and population—level growth rates seem to be determined independently.