Abstract An investigation was made of plant coexistence in coastal heaths. A 4 km stretch of Pleistocene beach sand was selected, and patterns of variation in heath vegetation on ridges and slopes in the beach system were studied. The sampling design covered variation with geographic distance among transects, plots within transects and quadrats within plots which were orthogonal to the alignment of ridges and slopes. Cover of vascular plant species was scored within each quadrat and both multivariate and univariate analyses tested the hypothesis that variation in the data was associated with environmental difference and geographic distance. There was a strong flohstic variation between the ridge and slope habitats. However, within these habitats there was no significant variation with distance at scales of kilometres, nor at hundreds of metres within transects nor at tens of metres within plots in floristic composition, in numbers of species, and in cover. Though differing floristically, the vegetation of the slopes and ridges had similar curves of importance values and fairly similar spectra of life forms and forms of post-fire regeneration in their constituent species, although the ridges had slightly more obligate-seeding species and fewer species of sedges and herbs than the slopes. The two habitats shared several genera, however, within such genera, species with similar attributes mostly occurred in different habitats.
Hypotheses were suggested to explain segregation of species between the two habitats and the coexistence of species within habitats. Since patterns of variation among habitats were consistent over both smaller and larger scales of distance examined, experiments to test hypotheses may be designed so that their findings might be applied generally to the whole system studied.