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Most adult EPTs (Ephemeroptera, Plecoptera and Trichoptera) disperse by flying upstream from their emergency site, following the water stream. Although it is generally assumed that riparian vegetation can facilitate the dispersion of many species, this relationship has not been properly characterized yet. The effects of riparian vegetation on landscape connectivity for EPTs can be assessed by analyzing differences in the EPT community structure: highly connected sites will host communities with a large proportion of weak dispersers and vice versa. Using the community structure to assess the relationship between riparian vegetation and landscape connectivity, allows for large scale analyses. In this research project, we first selected the most reliable method to assess the dispersion capacity of EPT communities. To do so, we compared the consistency and precision of several functional indices using experimental data. Then, we determined which environmental parameters, including the riparian forest, can predict the dispersion capacity of the EPT community. We confirmed a direct positive effect of riparian vegetation on EPT dispersion under certain conditions, and we also determined the most suitable spatial scale to apply our methodology. In the next step, we extended the analysis to different European biogeographical regions applying the conclusions from the previous study, aiming to find differences among distant geographical areas. Finally, we will try to predict changes in EPT phenology, as emergency periods, triggered by the increase or river water temperatures across the European continent, and how those changes could be ameliorated by riparian forest.

Die Studie zeigt die große Bedeutung der natürlichen bachbegleitenden Vegetation für unsere Bäche und Flüsse. Bäume sorgen für Beschattung, Stoffrückhalt, Uferstrukturierung und sind ein sehr artenreicher Lebensraum. In der Veröffentlichung werden zahlreiche nationale und internationale Facharbeiten ausgewertet und die ökologischen Funktionen genau beschrieben.Die daraus gewonnenen Erkenntnisse liefern für alle Akteure an unseren Fließgewässern wichtige Fachgrundlagen. Daneben wird allen Interessierten der große Wert von natürlichen Gewässerrandstreifen näher gebracht. Redaktionsschluss: 23.03.2022

Woody riparian buffers (hereafter, ‘woody buffers’) are frequently considered as important to mitigate the effects of stressors on streams and rivers. While several individual studies addressing nutrients, pesticides, water temperature and different biotic components support this conjecture, no study has addressed the effects of woody buffers on riverine biota at country-wide scales. We used a comprehensive dataset from sampling sites on 1082 catchments in France, comprising samples of benthic invertebrates, along with data on river size, physico-chemistry, hydromorphology, riparian and catchment land use and woody buffers at sampling sites and upstream. Using partial least square modelling, we delineated the effects of the different environmental variables on two benthic invertebrate metrics, separately for siliceous and calcareous rivers. Overall, models explained 49% (calcareous) and 39% (siliceous) of the variation in benthic invertebrate metrics. Direct effects of woody buffers on benthic invertebrate metrics were marginal, while physico-chemical conditions and catchment land use explained most of the deviance. Direct and indirect effects of woody buffer together covered up to 6% (upstream scale) plus 2% (local scale) of the explained variability. Synthesis and applications. In this national-scale study, on 1082 catchments, we investigated the potential of woody buffers to mitigate the effects of catchment-scale and local-scale stressors on macroinvertebrate biodiversity. Our results underline that the establishment of woody buffers is not necessarily a sufficient measure to solve the problem of deteriorating riverine macroinvertebrate communities, especially in catchments prone to intense land use. Nevertheless, two main outcomes included that local woody patches are not sufficient and that woody buffers should be established along longer river stretches. Also, accompanying catchment-scale measures should be promoted to reduce the effects of intense land use and pollution to a level that enables woody buffers to be effective as well.

River restoration is a main emphasis of river management in European countries. Cross-national comparisons of its implementation are still rare in scientific literature. Based on French and German national censuses, this study compares river restoration practices and monitoring by analysing 102 French and 270 German projects. This comparison aims to draw a spatial and temporal framework of restoration practices in both countries to identify potential drivers of cross-national similarities and differences. The results underline four major trends: (1) a lag of almost 15 years in river restoration implementation between France and Germany, with a consequently higher share of projects in Germany than in France, (2) substantial similarities in restored reach characteristics, short reach length, small rivers, and in "agricultural" areas, (3) good correspondences between stressors identified and restoration measures implemented. Morphological alterations were the most important highlighted stressors. River morphology enhancement, especially instream enhancements, were the most frequently implemented restoration measures. Some differences exist in specific restoration practices, as river continuity restoration were most frequently implemented in French projects, while large wood introduction or channel re-braiding were most frequently implemented in German projects, and (4) some quantitative and qualitative differences in monitoring practices and a significant lack of project monitoring, especially in Germany compared to France. These similarities and differences between Germany and France in restoration application and monitoring possibly result from a complex set of drivers that might be difficult to untangle (e.g., environmental, technical, political, cultural).

River biota are affected by global reach-scale pressures, but most approaches for predicting biota of rivers focus on river reach or segment scale processes and habitats. Moreover, these approaches do not consider long-term morphological changes that affect habitat conditions. In this study, a modelling framework was further developed and tested to assess the effect of pressures at different spatial scales on reach-scale habitat conditions and biota. Ecohydrological and 1D hydrodynamic models were used to predict discharge and water quality at the catchment scale and the resulting water level at the downstream end of a study reach. Long-term reach morphology was modelled using empirical regime equations, meander migration and 2D morphodynamic models. The respective flow and substrate conditions in the study reach were predicted using a 2D hydrodynamic model, and the suitability of these habitats was assessed with novel habitat models. In addition, dispersal models for fish and macroinvertebrates were developed to assess the re-colonization potential and to finally compare habitat suitability and the availability / ability of species to colonize these habitats. Applicability was tested and model performance was assessed by comparing observed and predicted conditions in the lowland Treene River in northern Germany. Technically, it was possible to link the different models, but future applications would benefit from the development of open source software for all modelling steps to enable fully automated model runs. Future research needs concern the physical modelling of long-term morphodynamics, feedback of biota (e.g., macrophytes) on abiotic habitat conditions, species interactions, and empirical data on the hydraulic habitat suitability and dispersal abilities of macroinvertebrates. The modelling framework is flexible and allows for including additional models and investigating different research and management questions, e.g., in climate impact research as well as river restoration and management.