Variety of the guiding image of rivers – defined for ecologically relevant habitat features at the meeting of the alpine, mediterranean, lowland and karst regions

Due to a long history of human intervention in river ecosystems, pristine conditions hardly exist nowadays and therefore a concept of a ‘guiding image’ defines the present-day potential natural state. Since regional physiographic factors influence the natural habitat features and biota on local level, also guiding images are expected to differ regionally. In this study, the guiding images of rivers of four major regions were defined: alpine, lowland, mediterranean and karst. The habitat features of rivers were studied in four major European regions: the Alps, the Pannonian Lowland, the Submediterranean region and the Dinaric region. For the analysis only those river habitat quality features were used that were proven to be ecologically important. The results showed differences among habitat features of rivers of all investigated regions. On the whole dataset the major gradient among reference sites was observed for habitat features that are in tight relation to water flow and sediment dynamics. For these features the major differences were found between the alpine and the lowland rivers, and on the other hand the similarities were observed between the Mediterranean and the Alpine rivers and between the karst and the lowland rivers. Another important gradient was observed on account of habitat features of riparian and channel vegetation. The highest values of these features were observed for the alpine and the mediterranean rivers and lower in the karst or the lowland rivers. However, the simpler riparian vegetation structure suggested by our results might not be the representative picture of natural vegetation, so the values of these features for a guiding image should be used with caution.In the present study the first step to the guiding images of the rivers in four major regions is proposed. Since the results showed considerable variability of some river habitat features present within regions, we suggest further investigation on even smaller groups. Nevertheless, the recognized differences and similarities among four regions in river habitat features that are ecologically relevant might serve as guidance for more sustainable and cost-effective river management.