Abstract
A simple model was developed to evaluate the material budget during the decomposition process of Phragmites australis aboveground biomass, and was applied to a reed stand in Neusiedlersee, Austria, to understand nutrient cycles. The model describes the growth of each organ of Phragmites australis, the collapse of standing dead shoot, the decomposition of leaves and stalks, and nutrient uptake and release of these processes. With a longer period of aerobic decomposition of litter before the litter was transferred to the anaerobic substrate the decomposition rate increased markedly especially from spring to autumn From 33% to 48% of the annual production was decomposed in a year and the rest remained in the anaerobic substrate, depending on the period of the aerobic decomposition of the litter. Releases of nitrogen and phosphorus were high from late spring to the end of summer, but were low and stable in autumn and winter A higher proportion of phosphorus than of nitrogen is expected to remain trapped in the anaerobic layer. Compared with nutrient. release, about 4 to 6 times more nitrogen and 5 to 7 times more phosphorus are taken up during the growing season.
