Sedimentation in salt marshes affected by grazing regime, topographical patterns and regional differences

Abstract

The future perspective of salt marshes strongly depends on a positive balance between sedimentation and an increased sea-level rise. Sedimentation itself is influenced indirectly by grazing as well as the position of the location in relation to the nearest sediment source and by amount and quality of the available sediment.

Two salt marshes were studied (Sönke-Nissen-Koog marsh, Friedrichskoog marsh) at the mainland coast of Schleswig-Holstein (FRG). In both marshes experimental plots had been established which were grazed by sheep at high and intermediate intensity or remained ungrazed. To figure out the effect of topography on net-sedimentation rate, we included sites close to and far from the locations „dike“ and „creek“ in all management variants. In general, a reversible soil shrinkage in summer due to desiccation could be detected.

Sedimentation rates differed significantly between grazed and ungrazed salt marshes. The ungrazedPuccinellia-dominated marsh as well as in theFestuca-dominated marsh demonstrated highest annual net-sedimentation rates of 1.8–2.1 cm and 1.2–1.7 cm, respectively, and can thus counterbalance the average sea level rise unless they show a decreasing trend in future.