The effects of various perturbations on leaf populations of Ammophila arenaria in various stages of a sand dune sere were studied over a period of almost two years. Fertilizer application markedly increased both the density and flux of leaves in young slack and old slack populations, where associated species were absent or rare; there was no change in population size or flux in more closed vegetation where a number of associated species were present. Sand accretion temporarily increased the flux in but not the density of the leaf populations. It is suggested that the decline in density of Ammophila in stabilizing dune seres is caused by the monopolization of nutrients by more shallowly rooting species.