Ecology and conservation of grassy wetlands dominated by spiny mud grass Pseudoraphis spinescens in the southern Murray-Darling Basin, Australia

The distribution, ecosystem functions, conservation status and threatening processes of grassy wetlands are reviewed, with an emphasis on changes in flood regimes, water resource development and land use. The focus of the review is the ecology of spiny mud grass Pseudoraphis spinescens (R.Br.) Vickery, a C₄ perennial aquatic grass. In Australia P. spinescens is a dominant species in grassy wetlands of the southern Murray-Darling Basin, the Wet-Dry Tropics and coastal New South Wales. Adapted to high irradiance and ambient temperatures, and to intermittent inundation for several months' duration, it is a rapidly growing (> 20mm d^-1), stoloniferous species, requiring prolonged, deep flooding interspersed with drying to achieve maximum growth and reproduction. Pseudoraphis spinescens can be considered an important species of grassy wetlands, providing food and habitat for waterfowl and other aquatic organisms through high primary productivity and nutrient cycling. Grassy wetlands in Australia are under threat from altered flood regimes, water resource development, grazing and land-use change. The provision of flood regimes that most closely match plant-specific water requirements represents the management action with the best prospect for the conservation of grassy wetlands on regulated rivers. A basic model for the water regime of P. spinescens grassy wetlands is presented to inform conservation and management, and stressing the need of such wetlands for large areas and rivers with high flow volumes that generate relatively deep prolonged flooding followed by drying out of the floodplain.