DISTRIBUTION, PRODUCTIVITY AND REPRODUCTIVE PHENOLOGY OF EMERGENT MACROPHYTES IN RELATION TO WATER REGIMES AT WETLANDS OF SOUTH-WESTERN AUSTRALIA

Variability in the response of Baumea articulata and typha orientalis to water regime was assessed at eight urban wetland lakes on the Swan Coastal Plain, south-western Australia. Distribution, productivity and reproduction along water regime gradients were assessed, and the importance of wetland nutrient status in altering plant response to water regime was also considered. The overall range in distribution observed across the lakes was similar for both species, but there was significant between-lake variation in distribution relative to mean water depth. Neither species occupied its full 'potential' distribution range, relative to water regime, at any one wetland. Standing biomass and ramet and inflorescence densities varied along the water regime gradient, with peak values generally occurring at intermediate water depths. There was a shift in phenology (ramet emergence, new leaf growth, flowering and seed production) with increasing mean water depth and nutrient status. Seasonal values of above-ground productivity changed along the water regime gradient for both species. Comparison of productivity at sampling points of different nutrient status but similar water regime showed a significantly greater growth response in T. orientalis compared with B. articulata. The significance of these results to urban wetland management is discussed.