Patterns in Plant Species Diversity and Composition of a Restored Nature-Based Solutions Floodplain

Floodplains are simultaneously among the most ecologically important and most severely impacted ecosystems in the world, with hydro-morphological alteration of riverine systems leading to declines in biodiversity. The loss of floodplain ecosystems worldwide increased interest in restoration projects throughout the world, centred around the concept of nature-based solutions (NBS). Floodplain restoration is increasingly regarded as one of the most successful forms of NBS. However, stream restoration projects lack in-depth monitoring practices, highlighting the need for evaluations of NBS restoration success on riparian vegetation. This study analysed patterns in plant species diversity and composition following restoration of the Bosscherveld floodplain, part of the Grensmaas Project, the largest nature-based river restoration project in the Netherlands. A total of 173 species were recorded over 325 quadrats. For each plot, hydro-geomorphological factors were analysed. Habitat type and water depth were key determinants of plant species distribution. Species richness significantly declined in relation to increasing hydrological stress, and vegetation was distributed according to species-specific tolerances to disturbance. Spatial coordinates, habitat type, sediment type, water percentage and depth all significantly contributed to differences in vegetation composition. Spatial variables emerged as the most significant contributors to the explained variation. The study concludes that the Bosscherveld floodplain displays high habitat heterogeneity and a significant presence of wetland species, aligning with initial restoration objectives. These findings underline the importance of monitoring to enhance the effectiveness of river restoration projects, ensuring the continued success of NBS initiatives in floodplain ecosystems.