A landscape approach towards ecological integrity of catchments and streams
Landscape ecology principles were applied to study how in-stream structures as well as terrestrial land cover and land use affect the ecological integrity of streams. Focusing on the role of habitat factors at multiple spatial scales of catchments as independent variables, macroinvertebrates, brown trout (Salmo trutta) and freshwater pearl mussels (Margaritifera margaritifera) were used as dependent response variables. Special efforts were made to capture the range of impacts along the gradient from altered to near-natural catchments in Europe's centre and north. With 25 catchments in the Carpathian Mountains in Central Europe as a landscape laboratory and a natural experiment design I studied the relationships between catchment land cover composition, riparian vegetation, and in-stream habitat characteristics on the one hand, and benthic macroinvertebrate assemblages on the other. The most important variables were at the terrestrial catchment level. The usefulness of data representing higher taxonomic levels and the use of the abundance of individuals from the orders Ephemeroptera, Plecoptera and Trichoptera, as surrogates for species richness was evaluated. Plecoptera was identified as the most effective group. Comparison of the abundance and taxonomic richness of the Plecoptera order in relation to catchment forest cover and water chemistry demonstrated the occurrence of non-linear response to forest cover. Using Swedish data I showed that it is possible to predict viable freshwater pearl mussel populations from riparian land cover, water chemistry and the abundance of the host fish species (brown trout). In another study a positive effect of woody debris on the abundance and size of brown trout in Swedish forest streams was observed. Altogether these results stress the importance of adopting a multiple scale perspective when assessing ecological integrity in riverine landscapes, from the amount of local in-stream structures as large woody debris (LWD) to the effects of riparian and catchment land cover composition and land use. To support implementation of EU policies about good ecological status a systematic landscape approach including (1) quantification of the ecological integrity concept, and (2) collaborative and communicative bottom-up participatory approaches to spatial planning need to be combined.