Pattern and Diversity in Swamp and Dune Vegetation, North Stradbroke Island

The pattern of plant species distribution, the richness of species composition, the distribution of resources among species and the manner of change in these parameters across landscapes are examined in three habitats on North Stradbroke Island. The closed-heath vegetation of a freshwater swamp, the grassland and low closed-forest of a frontal low dune sequence and the closed sclerophyllous forests of inland high dunes are studied by a variety of statistical techniques, including a new method for determining the degree and scale of microcommunity pattern. Of the three vege- tation types, the floristic diversity and complexity of spatial patterning within a small area is highest in the freshwater swamp vegetation. Not only is the scale of spatial variation smallest in this habitat, but the scale of patterning and co-association also becomes smaller as one proceeds into the swamp. The complexity of the vegetation is enhanced by a remarkably high species richness, a very low concentration of dominance and a high degree of intermingling of species. The floristic diversity and complexity of spatial patterning within such a small area of vegetation bears comparison with that of complex tropical rain-forest. The swamp vegetation appears to have undergone a high degree of speciation; at the same time, intermixture of species and the small scale of patterning have served as a means of minimizing intraspecific competition. If, like the tropical rain-forest, the ecosystem has evolved characteristics of rigid stability the system is likely to recover only slowly from major perturbation.