Geographical Variation in British Saltmarsh Vegetation

(1) A survey of 133 saltmarshes around the British coast showed that the majority of the 3000 releves recorded could be classified into fifty-eight noda. (2) The particular noda occurring at each site were used as attributes to study the relationships between the 133 saltmarshes by cluster analysis and principal coordinates analysis. (3) Three types of saltmarsh were recognized from the analyses. One type is largely restricted to south-east England, and at present is normally ungrazed; a second type is largely restricted to the Irish Sea coast of England and Wales, and most examples are grazed; the third type is characteristic of loch-head marshes on the west coast of Scotland. (4) It is suggested that these saltmarsh types have arisen through the interaction of sediment type, climatic, biotic and historic factors. Of these, the most important determinant of the vegetation-types on saltmarshes in England and Wales is past and present land-use. (5) An attempt is made to reconstruct what the vegetation might have been like in the absence of man's influence, using the present-day distribution patterns of a limited number of saltmarsh species. A regional differentiation of saltmarsh vegetation into four major 'natural' types is postulated. (6) The saltmarsh types occurring in Britain are compared with those described from elsewhere in north-west Europe.