We examined relations between vegetation and soils, using multivariate methods, in hitherto poorly-known upland swamps on the Woronora Plateau, south of Sydney. A major trend in floristic composition was related to the height and cover of the herbaceous stratum and reflected a gradient in soil moisture and nutrients. A second trend in floristic composition was related to the height and cover of the shrub stratum, and may reflect the influence of recurring fires on certain dominant shrub species. Five plant communities were recognized on the basis of floristic composition and were distinguishable by their different soil habitats and/or structural characteristics. We report some of the highest species-richness values in the world (at scales of 1-15 m2) for shrub/sedge-dominated vegetation, with up to 70 vascular plant species in 15 m2. Variation in species richness is inversely related to the resource gradient and positively related to the penetration of light through the vegetation canopy. This pattern is consistent with resource-competition models and warrants further investigation.
