ASSESSING FUNCTIONAL TYPOLOGY INVOLVING WATER-QUALITY, PHYSICAL FEATURES AND MACROPHYTES IN A NORMANDY RIVER

To carry out a functional typology of a Normandy watercourse, three co mpartments (water quality, physical features and macrophytes) were stu died in 74 stations. The data were analysed with multidimensional meth ods: Principal Component Analysis (P.C.A.), Hierarchical Cluster Analy sis (H.C.A.) and Multiple Factor Analysis (M.F.A.). P.C.A. analysis of the 3 compartments ordered significant variables as following : strea m order, water velocity and light, conductivity, pollution parameters as opposited to mineralisation ones, upstream/downstream, sciaphilous/ heliophilous, rheophilous, ditch species. All the compartments showed a longitudinal zonation pattern which characterised the first axis of M.F.A.. The second factor of M.F.A. was mainly due to water quality an d macrophytes, and the third one to physical features and macrophytes: macrophytes appeared to be reliable ecological integrators of the spa tial and functional heterogeneity. Four clusters obtained in H.C.A. de fined functional parts of the watercourse. This example of typology, a nd the relationships identified between the 3 compartments, assessed t he interest of macrophytes for characterising watercourses, and diagno sing their equilibrium.