Geratology and decomposition of Spartina versicolor in a brackish Mediterranean marsh

Abstract

Most studies on plant decomposition in salt marshes have been carried out in Spartina-dominated marshes in North America. In contrast, few have focused on marshes in Mediterranean systems. Moreover, research into litter decay in estuarine systems has been conducted with plant material collected before natural senescence and death. Here we followed the growth, senescence, leaf fall, and nutrient dynamics of Spartina versicolor to examine litter decay in a Mediterranean coastal system. We studied the dynamics of fungi, meiofauna and algae associated with detached S. versicolor litter, and the effect of the microenvironment (above and underneath wracks of dead Spartina) on decomposition. The exponential decay coefficient rate ( k, day −1) was higher for leaves attached to standing plants (0.0019) than after leaf abscission (0.0002–0.001). The decomposition rate of detached leaves was highly variable and depended on the position of the litter. The large differences in decomposition rates between the two experimental conditions indicate that the microenvironment affected the associated litter community during the initial phase of decay. Water availability and high temperatures over the sediment surface increased the density of meiofauna and epiphyton and decreased fungal biomass during the first 20 days of the experiment. Fungal biomass was at the lower end of reported values, probably as a result of the drier conditions and high salinity in the Mediterranean marsh. Spartina versicolor detritus acted as a nutrient sink by immobilizing large amounts of N and P for at least one year.