Vegetation of natural and stabilized riverbanks and early effects of removal of bank fixation

The majority of rivers in Europe has been dramatically altered in terms of their morphology and hydrology with severe consequences for the diversity and ecological functioning of the rivers and their floodplains. Consequently, an increasing number of river reaches has been restored over the past decades, often including the removal of bank fixation to reinitiate bank erosion and allowing for a rewidening of the rivers' cross-section. However, monitoring in detail the effect of such a measure on riverine vegetation is scarce. Using a Before-After-Control-Impact (BACI) design, we analysed the early changes of the vegetation 2 years after the removal of bank fixation at the Mulde River (central Germany). The results were compared with two types of control sites, representing a nonrestored as well as a natural riverbank that has never been fixed. We analysed differences in taxonomic and functional composition of the vegetation between bank types as well as community turnover after restoration. Two years after restoration, the vegetation differed clearly from the nonrestored sites. A substantial proportion of the community, especially the newly established species, became more similar to the natural bank community. Most importantly, spatiotemporal heterogeneity of the vegetation increased after removal of bank fixation, being an indicator for re-established dynamic processes similar to the natural site. The presented data serve as a baseline for a long-term monitoring and quantitative meta-analysis of restoration effects.

Automated summary

Rivers in Europe have been significantly altered in morphology and hydrology, leading to negative impacts on diversity and ecological functioning. In order to restore rivers, bank fixation has been removed and cross-sections have been widened. However, the effect of such restoration measures on riverine vegetation has been poorly studied. This research analyzed the early changes in vegetation following bank fixation removal in the Mulde River, Germany, and found that the restored sites had vegetation similar to natural riverbanks, indicating the reestablishment of dynamic processes.