SEASONAL WATER REGIMES AND LEAF-LITTER PROCESSING IN A WETLAND ON THESWAN COASTAL-PLAIN, WESTERN-AUSTRALIA

The effect of seasonal or permanent inundation on the processing of le af litter from two emergent macrophytes, Baumea artculata and Typha or ientalis, was examined at Lake Jandabup, a seasonal wetland on the Swa n Coastal Plain. Leaf litter processing was quantified through the los s of organic matter from leaf packs. The contribution made by microorg anisms was also examined. Leaf packs exposed to seasonal inundation ha d significantly higher losses of organic matter after six months than did those permanently inundated, with B. articulata leaf packs losing significantly more. The presence of a diurnally stratified water colum n in permanently inundated sites in summer, resulting in reduced oxyge n concentrations at the bottom of the water column, may be responsible for lower organic matter loss in this environment. These results are supported by the presence of organic-rich soils at permanently inundat ed sites and their absence at seasonally inundated sites, indicating a long-term pattern of leaf litter processing and wetland water regimes . The distribution of organic-rich soils in wetland basins may provide an indication of long-term water level regimes and can therefore prov ide a valuable tool for determining water regimes in artificially main tained or restored wetlands.