Litterfall in Casuarina glauca Coastal Wetland Forests

Abstract

Litterfall was measured over 3 years at two sites in coastal wetland forests dominated by Casuarina glauca Sieb. ex Spreng. in New South Wales. One site was in an incised river valley adjacent to the Hawkesbury River estuary, and the other site was in an open embayment adjacent to Botany Bay. Branchlets were the major litter component, followed by stems and infructescences. Significant year to year variation in branchlet fall correlated with storm events in one year. Overall, no significant differences in annual total litterfall were detected among sites and, averaged over all sites and years, the mean annual litterfall was 848 g m^-2. This suggests that coastal wetland forests dominated by C. glauca have some of the highest recorded annual litterfall rates for Australian temperate and subtropical forests. A flood event in the river valley site removed about 75% of the standing litter accumulated on the forest floor prior to flooding (1244 g m^-2). This suggests that accumulated organic matter and nutrients can be directly transported to estuarine ecosystems. Under non-flood conditions, however, these forests appear to act as organic matter and nutrient sinks.