Geographic variation in growth responses in Phragmites australis

Tidal restriction structures known as floodgates, are currently being investigated in Australia for their effects on altering coastal wetland ecosystems. Using litterbag techniques, a study was conducted at Tomago - an estuarine environment near Newcastle, NE, Australia, to investigate decomposition patterns of leaf litter of the grey mangrove (Avicennia marina Forsk (Vierh.)) on tidal and landward sides of two floodgates on a major tidal channel. After 360 days of litter incubation, significant differences were found between the landward and tidal wetland sites in rate and pattern of litter mass decomposition and in carbon, nitrogen and phosphorus elements remaining. Decomposition rates on the tidal side were similar to those reported in the literature for estuarine habitats, but were much greater than those of the landward side. Results suggest that litter on the tidal side of the floodgates receive daily tidal inundation and contribute more favourably to the estuarine food web than litter on the landward side.