The Role of Litter in Nutrient Cycling in a Brackish

The role of litter in nutrient cycling in a Typha angustifolia dominated brackish tidal marsh was studied with a field experiment. In replicated plots, litter was either removed, replaced with plastic strips (pseudolitter), increased threefold, or left unaltered. One set of plots received fortnightly surface applications of ammonium phosphate solution at an annual rate of 65 g/m2 of N and 72 g/m2 of P. The nutrient additions increased the concentrations of dissolved and extractable ammonium and phosphate, but decreased the concentration of dissolved nitrate plus nitrite in the sediment. The effects of the litter manipulations were mostly attributable to the physical structure of the litter layer rather than the decomposition process. Plots with no litter or pseudolitter developed higher concentrations of total NH, in the sediment than other plots. Also, when litter and pseudolitter were absent, the nutrient additions caused greater increases in PO, in the sediment. We measured decomposition and changes in nutrient content of Typha litter in mesh bags placed in the plots containing litter. In plots with increased litter, litter placed on the top of the litter layer decomposed faster than litter placed on the sediment surface. The experimentally manipulated litter took up nutrients during the experiment. The litter in plots with extra litter took up more N and P than was in total NH, and dissolved PO, in the sediment. However, litter decomposition did not affect inorganic N and P pools in the sediment, possibly because large pools of organic N and P in the sediment buffer the supply of inorganic nutrients against short-term changes in litter.