The effects of decreased management on plant-species distribution patternsin a salt marsh nature reserve in the Wadden Sea

To restore natural salt-marsh habitats, maintenance of the artificial drain age system was discontinued and cattle grazing was reduced in man-made salt marshes in the Dollard estuary, the Netherlands. We studied the vegetation development in these marshes shortly after these marshes became a nature r eserve, and again 8-9 years later. Cattle distribution showed a gradient of intensive use close to the landward seawall to a low or zero use more seaw ards. Elymus repens was mainly found at the highest elevations and in the l andward parts of the marsh, and lost much of its dominance. Conversely, Ast er tripolium increased landwards, and showed a shift to higher marsh elevat ions. These changes are explained by the interaction between increased soil waterlogging in the marsh, due to the neglect of the drainage system, and cattle grazing. Phragmites australis, Spartina anglica and Scirpus maritimu s were mainly found in the seaward parts of the marsh. Spartina anglica and Scirpus maritimus decreased strongly, partly through competitive replaceme nt by Phragmites australis and partly due to herbivory by greylag geese (An ser anser). Bare soil increased in depressions due to increased waterloggin g in the marsh combined with livestock grazing and goose grubbing. Phragmit es australis probably forms the climax vegetation in the brackish Dollard m arshes. Its increase in the seaward parts is irreversible in practice, but will benefit reed-bed breeding birds. On the landward side, the combination of neglect of the drainage system with moderate grazing may be effective i n maintaining young successional stages suitable for a wider range of halop hytic plants, and for breeding redshank and grazing waterfowl. (C) 2000 Els evier Science Ltd. All rights reserved.