Alluvial Stratigraphy and Vegetational Succession in the Region of the Bure Valley Broads: III. Classification, Status and Distribution of Communities

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Abstract
A classification of the plant communities of the Bure valley broads is advanced on the basis of data set out in the two preceding papers of the series. Three main types of primary succession are recognized within the basins of the broads themselves:- 1) The Carex paniculata type, in which a reedswamp of Typha angustifolia (with or without preceding Scirpus lacustris) is replaced progressively by Phragmites communis, by Carex paniculata tussock-fen, and finally by swamp carr; 2) The Carex acutiformis type, with similar initial stages, but with Carex acutiformis becoming dominant at the late fen phase, and leading ultimately to semi-swamp carr; and 3) The Cladium mariscus type, with Cladium forming the main fen dominant, and with fen carr as the real or apparent climax. The succession on the solid substrates lateral to the broads is simpler, with Phragmites leading directly to fen carr or to anthropogenic fen communities maintained by mowing. Colonization of peat cuttings showed essentially similar initial stages to those of the natural broads, but with later modifications correlated with the presence of a hard peat bottom and with more intensive anthropogenic factors. The distr. of the main types of succession within the various broads is attributed to differences in water movement, due to the progressively greater distance of the downstream broads from the river, and to the presence or absence of direct tidal connections. It is also tentatively suggested that the greater abundance of Cladium in the past, demonstrated by a number of profiles of surface peats, may be due to changes in tidal range within the river in comparatively recent times.