Suburban development and resultant changes in the vegetation of the bushland of the northern Sydney region

Bushland sites in the northern suburbs of Sydney were compared to sites in Brisbane Waters National Park, Ku‐ring‐gai Chase National Park and Royal National Park which are relatively unaffected by suburban development. Both shale‐derived and sandstone‐derived soil in four physiographical locations were examined, with three replicates of each of the 16 combinations. Phosphorus levels are higher in the soils of suburban sites compared to soils derived from similar rock bases in non‐suburban sites. Phosphorus levels are also higher on shale‐derived than on sandstone‐derived soils, and lower on hilltops than in other physiographic positions. Suburban sandstone sites have soil phosphorus levels similar to those of non‐suburban shale sites. Three major and three minor clusters of species were distinguished using a hierarchical agglomerative clustering. The major clusters consisted of (1) species commonly associated with wet sclerophyll forests and rainforest margins, (2) species directly or indirectly related to the presence of man, and (3) species associated with dry sclerophyll forests and heaths. Using analyses of variance and covariance, and logit models, the abundance of the first main cluster was related to nutrient‐rich soils and the abundance of the third main cluster to low nutrient soils whereas the presence of the second main cluster was almost entirely restricted to sites surrounded by suburbs. The development of suburbs around vegetation patches has led to an increase in the abundance of native and exotic mesomorphic species and the addition of phosphorus to the soils. The data presented in this paper indicates that high phosphorus levels and presence of mesomorphic species are related.