Decomposition dynamics of Phragmites australis litter in Lake Burullus, Egypt

This study estimated the decomposition rate and nutrient dynamics of Phragmites australis litter in Lake Burullus (Egypt) and investigated the amount of nutrients released back into the water after the decomposition of the dead tissues. Phragmites australis detritus decomposition was studied from April to September 2003 utilizing the leaf, stem, and rhizome litterbags technique with coarse mesh (5mm) bags on five sampling dates and with nine replicate packs per sample. All samples were dried, weighed and analyzed for N, P, Ca, Mg, Na, and K concentrations. The exponential breakdown rate of leaves (-0.0117/day) was significantly higher than that of rhizomes (-0.0040/day) and stems (-0.0036/day). N, Na and K mineralization were the highest from leaf litter, followed by rhizomes and stems, while P, Ca and Mg mineralization were the highest from rhizomes, followed by leaves and stems. The dead shoot biomass at the end of 2003 amounted to 4550g DM/m(2) which enters the decomposition process. By using the decay rate of 0.0117 and 0.0036/day for the leaves and stems, 3487g DM/m(2) is decomposed in a year, leaving only 1063g DM/m(2) after 1year. This is mainly equivalent to releasing the following nutrients into surrounding water (in g/m(2)): 24.4N, 1.1P, 15.5Ca, 3.5Mg, 11.3Na and 16.7K. In conclusion, the present study indicates a significant difference in relation to the type of litter; these breakdown rates were generally greater than most rates reported in previous studies that used the same technique and mesh size.