Plant species associations with alkaline environments associated with artesian spring wetlands

Aims To describe the physico-chemical environment of artesian spring wetlands and surrounding scalds; to identify the association of plant species with these factors; and to assess the tolerance of a wetland species to an alkalinity gradient. Methods Surface soils were sampled for chemical attributes and water depth in spring wetlands and associated scalds. Plant species were recorded in quadrats and their distribution in relation to physico-chemical attributes assessed. Comprehensive analyses of salt composition and mineralogy were conducted at scald sites. An experiment was conducted to assess the tolerance of theartesian spring wetland species Eriocaulon carsonii . Results The wetlands of artesian springs have circumneutral pH with low salinity. The environment around the wetlands has extremely high pH, dominated by sodium bicarbonate minerals, but have variable salinity. The plant species, many of which are endemic, have clear associations with individual habitats including the permanent pools, the fringing scalds and the terrestrial scalds without sub-surface groundwater. Eriocaulon carsonii is tolerant of neutral and alkaline waters but not highly acidic water. Conclusions The permanent pools supported by artesian springs have low salinity and neutral pH. The scalded areas around springs are extremely alkaline and can have high salinity values. The chemistry of the springs described here are of the Na-carbonate type and typical of the Great Artesian Basin. The evolution of endemic wetland species may have resulted from the permanence of the pools rather than distinctive chemistry. By contrast the species of the scalds are specialised to an extreme chemical environment.