Three decades of coastal vegetation dynamics in the Castelporziano Presidential Estate: analysing biodiversity shifts in an exceptionally intact coastal dune system

Abstract Mediterranean coastal dunes are among the most threatened ecosystems in Europe. Analysing temporal trends in a site with exceptionally well-preserved zonation and minimal anthropogenic disturbance offers a unique opportunity to deepen our understanding of vegetation dynamics under low-impact conditions in these vulnerable ecosystems. This study examines the temporal dynamics of coastal dune ecosystems within the Castelporziano Presidential Estate, which hosts intact Mediterranean dune systems with complete vegetation zonation. Revisiting 80 historical plots initially surveyed 30 years ago, we analysed changes in plant species occurrence and abundance over time using ordination and similarity percentage analysis. Additionally, we assessed shifts in typical, ruderal, and alien species, ecological indicator values, and an index based on rhizomatous geophyte grasses to evaluate the system’s erosion control capacity. Our results revealed no significant decline in species richness in foredunes and dune grasslands, contrasting with trends observed in other coastal dunes in Central Italy. Instead, we recorded an increase in typical species abundance in foredunes, likely resulting from limited human disturbance over the past 30 years. These changes are probably related to ongoing successional dynamics. Coastal shrublands underwent more pronounced changes, transitioning toward woodlands and experiencing an increase in typical species. These transformations suggest positive successional shifts. Our findings indicate that the coastal dune ecosystem is well-preserved, largely due to restricted human disturbance and effective management. This study underscores the value of resurveying methodologies for monitoring vegetation dynamics, offering critical insights to support conservation efforts for these unique Mediterranean habitats.