Seasonal water regimes and leaf litter processing in a wetland on the Swan Coastal Plain, Western Australia

Abstract

The effect of seasonal or permanent inundation on the processing of leaf litter from two emergent macrophytes, Baumea articulata and Typha orientalis, was examined at Lake Jandabup, a seasonal wetland on the Swan Coastal Plain. Leaf litter processing was quantified through the loss of organic matter from leaf packs. The contribution made by microorganisms was also examined.

Leaf packs exposed to seasonal inundation had 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 column in permanently inundated sites in summer, resulting in reduced oxygen 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 inundated 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 provide a valuable tool for determining water regimes in artificially maintained or restored wetlands.