The influence of vegetation on erosion and accretion in salt marshes of the Oosterschelde,The Netherlands

The total root strength of two plant species (Spartina anglica and Limonium vulgare) is related to salt marsh cliff erosion in the Krabbenkreek (Oosterschelde). A ranking order in cliff stability is predicted on the basis of these root strength calculations. It turns out that the S. anglica root system is more effective in reducing lateral cliff erosion than the root system of L. vulgare. Also the establishment of S. anglica by germination of seeds is studied in relation to the erosion/deposition rates at an accretion site in the Krabbenkreek. The percentage of seeds washed away depends on the mobility of the superficial sediment which increases with decreasing height above N.A.P. (Dutch Ordnance Level). Above 0.90 m + N.A.P. a germination of 20% is measured, but seedlings survive the winter period only in the zone where a patchy vegetation already exists. It is concluded that generative spread of S. anglica in the Krabbenkreek is not very likely under the present hydrodynamic conditions.Nomenclature follows Heukels & van Ooststroom (1977).Acknowledgement: The research presented herein was carried out at the Delta Department, Environmental Division of the Ministry of Transport and Public Works, Middelburg. This work forms part of the research on salt-marsh ecosystems of the Oosterschelde. Assistance with sowing and sampling was given by the Field Survey section of the Environmental Division. Analyses of root weight and root diameter were carried out by the Institute of Soil Fertility in Haren by order of the Environmental Division. I gratefully acknowledge Ir A. de Jager and J. Floris of this institute for putting a special sampling auger at my disposal. G. den Hartog, P. van Vessem and Drs P. M. Schoot of the State University of Utrecht are thanked for their assistance during the study. Special thanks are due to Drs J. M. Roels for this critical editorial review of this paper.