Seed banks, community dynamics and species persistence in 5 Tasmanian temporary wetlands

Water regime has been found to be the most important factor in determining vegetation patterns in wetlands. The present study investigates the short and long-term persistence of plant communities within 5 temporary Tasmanian lentic wetlands and- resistance and resilience of wetland communities to dry periods. Within each wetland an aquatic herbaceous and sedge-dominated zone were sampled seasonally between February, 1997 and November, 1998, to test difference between and within wetlands, and their relations to water depth. Four glasshouse experiments using sediments taken from 9 permanent quadrats per vegetation type per wetland (zone) were used to determine temporal and spatial differences in seed banks in relation to season, vegetation type, depth, germination treatment and water regime. The relationship between the seed bank and extant vegetation was investigated. A functional group classification generated similar groups to Brock and Casanova (1997). These were: a) submerged; b) amphibious fluctuation responder; c) amphibious fluctuation tolerator-emergent; d) amphibious fluctuation tolerator-saturated/mudflat; and e) terrestrial. The vegetation communities within the 5 temporary wetlands proved not resistant to changes in water level. Large differences in percentage cover were associated with hydrological changes over the 2 year period. However, the communities were able to resurrect relatively quickly after both short and long term dry periods. The seed bank experiments indicated that Tasmanian temporary wetlands have speciesrich persistent seed banks, and, therefore, the potential for future regeneration. In general, species in the seed bank could be related to species found in the extant vegetation. However, at any given time, species can be found in the seed bank and not present in the extant vegetation, or vice versa. Both seed banks and vegetative regeneration were important mechanisms for species persistence in the vegetation communities of the 5 wetlands.