Temporal variation in recruitment and mortality for the pasture weed Hieracium floribundum: implications for a model of population dynamics.
3-fold differences in annual recruitment and 8-fold differences in annual mortality were recorded for H. floribundum between 1975 and 1983. Annual variation in the effects of herbivores accounted for most of the changes; recruitment may also have been influenced by the availability of soil moisture early in the growing season. Weed population density increased more slowly than predicted by a mathematical model because the model did not allow for temporal variation in recruitment and mortality. After 6 years, the predicted density averaged 60% greater than actual density.