The role of river dynamics in the conservation of dry river grasslands

Question

In what way and to what extent do river dynamics determine the development, conservation and restoration of dry river grasslands?

Location

The River Meuse is one of the larger Northwest European streams with nature protection that places emphasis on river corridor plants in dry river grasslands. The Common Meuse reach is a 30km unregulated river stretch at the border between Belgium and the Netherlands.

Methods

The grasslands of the alluvial plain were mapped and sampled with vegetation relevees and soil sampling. Spatial information gathered using GIS was added to this data matrix, and a hydraulic model added river variables of flood frequency and flow velocity. Ordination and diversity analysis was carried out to link composition and diversity aspects to soil conditions and river dynamics, the results of which were used to build a community distribution model. As the dry river grassland is a threatened vegetation type, an analysis of species at risk was performed to find key constraints and define effective restoration measures.

ResultsFlood dynamics, soil conditions and management proved to be determining aspects for the composition and diversity of river grassland. The different dry river grassland communities were clearly distinguished by soil pH and salt concentration – soil variables that were significantly correlated to the flood regime. The group of river corridor plant species studied were good indicators of well developed dry river grassland patches. The significant isolation aspect of the dry river grassland relicts was found to be due to recruitment limitation, as a consequence of habitat fragmentation linked to land use intensification and river regulation. As the habitat creation process is the trigger for sustainable conservation, a spatial model based on hydraulic modelling using GIS allowed the prediction of potential dry river grassland development and gave insight into spatial and management requirements for conservation strategies.Conclusions

Knowledge of habitat conditions and dynamics is essential when forming conservation strategies for dry river grasslands. The river corridor plants proved to be a good flagship species group for the protection and restoration effort.