Wallum is the regionally distinct vegetation on coastal dunefields, beach ridge plains and sandy backbarrier flats in subtropical northern NSW and southern Queensland (22°S to 33°s). This study examined floristic patterns in the wallum and allied vegetation along 400km of coastline in north-eastern NSW. Floristic and environmental data were compiled for 494 quadrats allocated on the basis of air photo pattern and latitude. A phytosociological classification displayed strong congruence with an initial classification based upon photo pattern, especially for single stratum vegetation, thereby suggesting that API (air photo interpretation) is a valuable technique for the recognition of floristic assemblages. The utility of API for depicting the spatial distribution of tallest stratum species in multi-stratum vegetation was also confirmed. Nonetheless, photo signatures of the tallest stratum are less satisfactory as surrogates for identifying noda for the full complement of species in multi-stratum vegetation. Ordination supported the numerical classification, and reinforced the value of API for capturing meaningful biological and environmental data. Plant-environment relationships were examined for a range of variables. The consistent trend to emerge was a comparatively strong correlation between floristic composition and topographic position, and in some instances also between floristic composition and geology. Mean species richness at the 25m² scale was lower in wetter habitats, although differences were not consistently significant.

The east Australian coastline supports regionally distinct heathlands and allied structural formations, and of particular interest is the vegetation on Quaternary dunefields and beach ridge plains containing aquifers. Groundwater is abstracted from these aquifers for domestic, industrial and agricultural consumption, and this abstraction proceeds without a sound understanding of plant–water relations. This study examined relationships between the vegetation and a range of simple and complex environmental variables. Aspects of intra-habitat and micro-site environmental heterogeneity were also explored. Watertable depth varied spatially and temporally relative to vegetation type, although differences were not consistently significant. Differences in watertable depth were significant for vegetation samples grouped by topographic position. Plant roots were invariably present at the upper boundary of the aquifer and these were observed at depths of up to 10.5 m. Groundwater was found to have the chemical composition of dilute seawater. Soil properties for the A1 horizon (total phosphorus, total nitrogen and organic matter content) varied with vegetation type and topography, and although mean values were generally higher in wetter habitats, differences were not consistently significant. Ordination identified topography as the more important determinant of vegetation pattern. Intra-habitat and micro-site differences in soil and groundwater properties were detected, and the likely causes of this variation are discussed.