Biotic and abiotic characterisation of embankment vegetations along navigable waterways in Flandres

In Europe the area of traditionally managed semi-natural grassland habitats has been reduced dramatically during 20th century. In highly fragmented landscapes with few or very small semi-natural habitats left, embankments and other small habitat patches can have an ecological importance for the maintenance of semi-natural grassland species and in improving ecological processes. Consequently, a better knowledge of abiotic variables affecting biodiversity in small habitat patches is desirable.
We studied the vegetation and expected determining abiotic variables in embankments along navigable waterways in Flandres. In total 542 vegetation relevés (of 4 m2) were made on the slope or crown of embankments along 6 different waterways. By means of TWINSPAN main clusters of vegetation composition were distinguished. Soil variables were determined in 200 plots, selected in such way that plots were equally distributed in main vegetation clusters.
TWINSPAN showed 5 main clusters of vegetation types: cluster 1 characterised by Cytisus scoparius, Rumex acetosella and Rubus sp.; cluster 2 differentiated by Festuca rubra, Achillea millefolium, Daucus carota, Leucanthemum vulgare and Centaurea jacea; cluster 3 typified by Holcus lanatus and Arrhenatherum elatius; cluster 4 classified by Urtica dioica, Galium aparine, Anthriscus sylvestris and Elymus repens and cluster 5 distinguished by Symphytum officinale and high coverages of Urtica dioica and Galium aparine.
Highest mean number of species and Shannon Wiener diversity was noted in cluster 2; lowest in cluster 5. Lowest mean Ellenberg indicator value for nutrients was observed in cluster 1; highest in cluster 5. Soil variables showing important differences in the main vegetation clusters were cation exchange capacity, mineral nitrogen and total phosphorous. Mean values for these soil variables were lowest in cluster 1 and highest in cluster 5.
Understanding the influence of abiotic variables on vegetation composition can contribute to an appropriate ecological conservation, management or restoration of embankments along navigable waterways.