TEMPORAL AND SPATIAL ENVIRONMENTAL VARIABILITY IN THE UPPER RHONE RIVER AND ITS FLOODPLAIN

1. This paper develops a framework of spatial and temporal variability for a habitat typology of the Upper Rhone River (France) and its allu vial floodplain that is based on about 17 years of data collection and analysis. The aim was to provide a scale of spatial-temporal variabil ity for river habitat templet predictions on trends in species traits and species richness. 2. In developing this framework, eight physical- chemical variables were available and could be considered for twenty-t wo habitat types: seventeen superficial (surface) and five interstitia l (0.5 m below the substrate surface). These habitat types were select ed in two areas (Jons and Bregnier-Cordon) after geomorphological cons iderations.and because of differences in their biological characterist ics. 3. The data sets used were processed by a 'fuzzy coding' method u sing, for each variable, the frequency distribution (by modalities = c ategories) of all measurements and monthly means over an annual scale. Two tables were produced; the first corresponded to an expression of the total variability, and the second represented an evaluation of the temporal variability. 4. Each of these tables was analysed by corresp ondence analysis, which provided factorial scores that were used to ca lculate, by habitat type and by variable, a total variability and a te mporal variability in terms of cumulated variability of factorial scor es for the eight physical-chemical variables. The rationale in describ ing variability from these two tables is that total variability equals temporal variability plus spatial variability. The spatial variabilit y was then determined by the difference between total and temporal var iability. From this procedure, a positioning of the twenty-two habitat types on the spatial and temporal variability axes was obtained. 5. T he estimate of spatial variability did not consider any error term tha t may have occurred in the above model; it was then tested by an indep endent assessment of the spatial variability using thirteen variables in nine major habitat types. A high correlation between the two ways o f assessing spatial variability (r = 0.85, P < 0.004) underscored the reliability of the spatial variability that was calculated previously. 6. The river habitat templet obtained for the Upper Rhone and its all uvial floodplain appears to be appropriate to test the predictions on patterns of species traits and species richness in the framework of sp atial and temporal variability.