Coastline Dune Vegetation Dynamics: Evidence of No Stability

Coastal dune ecosystems are subjected to severe stress and disturbance factors that are particularly high in the beach-foredune environment and generally decrease with distance from the coast. The present study aimed to link plant species composition of coastal foredunes with the physical dynamical processes of the coastline in central Italy. A random hierarchical sampling design, based on two spatial scales (quadrant and parcel), was applied to estimate the variation in plant community composition. Permutational multivariate analysis of variance (PERMANOVA) revealed an approximately similar amount of variation with respect to both the coastal dynamic class and the parcel level. In addition, principal coordinate analyses showed that three taxa - Ammophila arenaria, Elymus farctus and Otanthus maritimus subsp. maritimus - were mainly linked to the coastal dynamics: A. arenaria increases its abundance where erosion of the shoreline is very high, while E. farctus and O. maritimus are more abundant in the prograding coast. Finally, similarity percentages analysis (SIMPER) highlighted that where the erosive processes were strongest, the number of the species contributing to the total similarity was the highest. This is likely to indicate instability and a strong disturbance of plant communities that results in an unstable equilibrium. These findings have important implications for management and conservation actions.