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

Abstract

NEUHAUS, R & STELTER, TH. & KIEHL, K. (1999): Sedimentation in salt marshes affected by grazing regime, topographical patterns and regional differences. -Senckenbergiana marit., 29 (Suppl.): 113-116, 4 figs.; Frankfurt a. M.]The future perspective of salt marshes strongly depends on a positive balance between sedimenta'don and ah 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 (S6nke-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 oftopography 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 siguificantly between grazed and ungrazed salt marshes. The ungrazed Puccinellia-dominated marsh as well as in the Festuca-dominated marsh demonstrated highest annual netsedimentation 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.

Effects of livestock species and stocking density on accretion rates in grazed salt marshes

“…In contrast, in the higher elevated Festuca-zone, where accretion rates were lower, no effect of grazing was found (Andresen et al, 1990). Similar differences between two zones within one marsh were detected by Neuhaus et al (1999). A largescale study including the entire coast of Schleswig Holstein also found grazing to only have an effect in the northern part of the study area, where rates of surface elevation change were higher (Suchrow et al, 2012).…”

“…Despite this, nature management decisions to date hardly took into account possible effects of grazing on accretion rates. Strong evidence for a reduction of accretion rates in grazed marshes was found in various studies (Andresen et al, 1990;Neuhaus et al, 1999;Stock, 2011;Elschot et al, 2013). In contrast, Nolte et al (2013b) did not find any overall clear effect of grazing on accretion rates.…”

“…In contrast, Nolte et al (2013b) did not find any overall clear effect of grazing on accretion rates. In addition to the comparison of grazed vs. ungrazed marshes, the stocking density was also found to influence accretion rates with lower rates at higher stocking densities (Andresen et al, 1990;Neuhaus et al, 1999;Stock, 2011). The effect of stocking density is of great importance for nature management (Dumont et al, 2007;Scimone et al, 2007;Dumont et al, 2009), as it is necessary to choose a stocking density to reach management goals (e.g.…”

“…A tall and dense vegetation structure slows down the current of the inundating water and thereby promotes sediment deposition (Neumeier and Amos, 2006;Viles et al, 2008;Fagherazzi et al, 2012). An important factor that strongly affects these physical vegetation structure indices in salt marshes is livestock grazing (Andresen et al, 1990;Neuhaus et al, 1999;Stock, 2011;Suchrow et al, 2012).…”

Directional and non‐directional vegetation changes in a temperate salt marsh in relation to biotic and abiotic factors

“…3.3 ± 1 mm per year at the German North Sea coast (Führböter 1989). In many salt marshes this rise can be counterbalanced by sedimentation (Esselink et al 1998;Neuhaus et al 1999). In the Hamburger Hallig salt marsh, there is a distinct gradient with sedimentation rates much higher than sea level rise at the north-west exposed areas of the marsh close to the intertidal flats and with hardly any accretion in the central areas (Fig.…”