Evaluation of dune rehabilitation after 95 years by comparison of vegetation in disturbed and natural sites

Disturbed and natural sites are compared in a belt of rehabilitated coastal dune on the Tyrrhenian coast of Italy. The goal was to evaluate rehabilitation success by comparing structure and plant composition in three different vegetation types. Vegetational attributes were used to indicate the trajectory of the vegetation dynamic, by recording increases or decreases in these parameters. The variations in attributes and similarities in composition were investigated using multivariate methods. In general, significant changes between the disturbed and natural sites were indicated by a decrease in annual graminoids, trees, and wind-dispersal species and an increase in rare species. In the rehabilitated site, there was a high rate of recruitment of wind-dispersal species, and rehabilitation seems to have been successful from the point of view of the decrease in annual graminoids and increase in rare species. However, each vegetation type of dune environment was associated with a different number of attributes and different rehabilitation success. Specifically: (i) open sands with annual vegetation growing along drift lines were the most similar among the three sites, from the point of view of both structure and species composition, and are therefore the easiest to rehabilitate; (ii) dunes partially or densely vegetated by herbaceous species showed an increase in rare species in the natural site and were characterized by successful rehabilitation; (iii) dunes densely vegetated by shrubs differed significantly between sites and are consequently the most difficult to rehabilitate. Our comparisons suggest that initial planning efforts should focus on this last type of vegetation cover.