ALTERATION OF PATCH BOUNDARIES ON THE FLOODPLAIN OF THE REGULATED RIVER TRENT, UK

Investigations were carried out into the contemporary distribution and structure of the vegetation communities at Gunthorpe, Nottinghamshire on the floodplain of the River Trent. A 60 km reach of the river was examined to determine the overall distribution and structure of vegeta tion communities; the Gunthorpe site was chosen as a representative ex ample. Three hundred and thirty-nine separate plots were examined and the site contained 132 species. It is clear that the extent of zones o f discontinuity or transition (ecotones) between different vegetation patches has decreased due to long-term land-use management. The overal l number of vegetation patches has also been reduced. A hierarchy rela ting boundaries to external influences is proposed and the relationshi p of ecotones to more clearly differentiated patch habitats identified . Highest species diversity is seen to be associated with the transiti on zones or ecotonal habitats, particularly under conditions of modera te disturbance intensity. It is concluded that the ecotones remaining still provide a habitat for a wide range of species with differing aut ecological requirements, but all typical of less disturbed alluvial me adows and marshes. These zones of transition potentially provide a poo l for species expansion given improved ecological conditions following river restoration measures.