Vegetation development on newly embanked sandflats in the Grevelingen (The Netherlands) under different management practices

Slim, P.A.; Oosterveld, P.


In 1971 the Grevelingen estuary was embanked. In the newly created lake Grevelingen the tidal movements stopped and a few thousand ha of sandflats fell permanently dry. Ca 40% of the surface of those flats was immediately afterwards sown with rye and other grasses to prevent wind erosion. This fixation of a rather uniform environment resulted in a monotonous vegetation cover. Grazing with domestic animals is now applied as management practice to create more environmental variation and thereby a higher species diversity.
The present study gives the results of eleven years of comparing vegetation development under various management practices, including non-interference in the spontaneous and sown vegetation. Sequential vegetation mapping, repeated inventories of selected areas and studies in permannent plots are the main techniques used.
On the unsown shore zones interesting vegetation types are developing where species diversity is higher than in the sown areas. In the shore zones not only a faster succession occurred compared with the sown areas, but also a shifting of environmental gradients, e.g. in moisture and salinity conditions, encouraged vegetation changes. After 10 yr grazed areas had a higher number of species than ungrazed equivalent areas. The results also indicated that grazing slows down the establishment of (tall) woody species and shrub development.