Context-specific positive effects of woody riparian vegetation on aquatic invertebrates in rural and urban landscapes

1. Woody riparian vegetation (WRV) benefits benthic macroinvertebrates in run- ning waters. However, while some functions are provided by WRV irrespective of surrounding and catchment land use, others are context-specific. In recent large-scale studies, effects of WRV on macroinvertebrates were therefore small com- pared to catchment land use, raising the question about the relevance of WRV for restoration.2. Model- based recursive partitioning was used to identify context-dependent effects of WRV on the macroinvertebrates' ecological status in small (catchment area 10- 100 km2) lowland (n = 361) and mountain (n = 748) streams. WRV cover was quantified from orthophotos along the near (500 m) and far (5000 m) up- stream river network and used to predict the site's ecological status. Agricultural, urban and woodland cover at the local and catchment scales along with hydro- morphology were considered as partitioning variables.3. In rural agricultural landscapes, the effect of WRV on the ecological status was large, indicating that establishing near-upstream WRV can improve the ecological status by as much as two of the five classes according to the EU Water Framework Directive.4. Even in urban landscapes, effects of far-upstream WRV were large if catchments had a moderate share of agricultural land use in addition. The beneficial effects of WRV were only limited in purely urban catchments or in a multiple stressor context.5. Synthesis and applications. While woody riparian vegetation (WRV) can even improve the ecological status in urban settings, it is especially relevant for river management in rural agricultural catchments, where developing WRV potentially are effective measures to achieve good ecological status.

Automated summary

Woody riparian vegetation (WRV) provides significant benefits to benthic macroinvertebrates in both rural agricultural and urban landscapes, improving ecological status. However, the effects of WRV are context-specific, being more pronounced in rural agricultural catchments and in urban areas with moderate agricultural land use. WRV's beneficial effects are limited in purely urban catchments and in a multiple stressor context.