Relationships of some ecological factors with the associations of vegetation in British rivers

During River Habitat Surveys on the physical structure of watercourses in B ritain between 1995 and 98, detailed assessments of the floristic associati ons, physical habitat and water chemistry were made at 165 sites over a wid e range of vegetation types. Botanical data from a total of 340 releves fro m within these RHS were recorded. The vegetation was classified phyto-socio logically on the basis of the abundance of characteristic species, resultin g in 45 aquatic, swamp and mire associations being identified together with nine other communities which could not be completely classified phyto-soci ologically. The associations were assigned to 22 alliances, 13 orders and 1 1 classes excluding communities dominated by filamentous algae. Water enric hment (as soluble and total phosphorus) was the most significant factor for the differentiation of the communities but pH, conductivity and alkalinity were also important.