Vegetation patterns of permanent spring wetlands of arid Australia

A transect-based quadrat survey was conducted within 11 spring wetlands fed by permanent groundwater flows from the Great Artesian Basin at Elizabeth Springs in western Queensland. Flow patterns within individual wetlands change with sedimentation associated with mound building, siltation of abandoned drains and changes in aquifer pressure associated with artificial extraction from bores. The pattern of floristic groups for the wetland quadrats was poorly related to soil texture, water pH, slope and topographic position. Patterns were most clearly related to wetland age as determined from aerial photography, with a clear successional sequence from mono-specific stands of Cyperus laevigatus on newly formed wetland areas to more diverse wetland assemblages. However, evidence from other Great Artesian Basin springs suggests that succession can also result in reduced species richness where the palatable tall reed Phragmites australis develops mono-specific stands.