Vegetation dynamics within afforested coastal areas: regeneration by native species or invasion by alien species?

During the last century, massive reforestation projects along the dunes of the southern Sicily have been carried out. Such interventions, far from being in line with the current trends of close-to-nature silviculture, are, however, particularly interesting to assess the vegetation dynamics in afforestation areas. Furthermore, these kind of interventions may determine two opposite effects, that is renaturalization by native woody species or invasion by alien species. Acacia spp. are among the most widespread and prominent invaders within Mediterranean-climate areas, where they have already shown the capability to deeply change the characters and the functioning of native ecosystems. For instance, Acacia longifolia (Andrews) Willd. may successfully invade the understory of pine forests, causing the alteration of the water balance and carbon storage of the whole forest ecosystem. In Sicily, especially in the last decades, Acacia saligna started to abundantly regenerate in many natural and semi-natural areas, with a stark preference for dune and coastal afforested sites. The nature reserve “Foce del Fiume Platani” represents an excellent case study in this respect.