P. Esselink et al., The effects of decreased management on plant-species distribution patternsin a salt marsh nature reserve in the Wadden Sea, BIOL CONSER, 93(1), 2000, pp. 61-76
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.