Temporal changes in the vegetation of Italian coastal dunes: identifying winners and losers through the lens of functional traits

摘要

Plant communities of coastal dunes are highly biodiverse and greatly valued for the services they provide, yet they are also threatened by global change and are often neglected in conservation planning. To determine the long-term effectiveness of conservation actions on Mediterranean coastal dunes, here we focus on Italy's coastline and (i) assess how the vegetation cover of the major psammophilous habitats and species has changed since the 1960s, (ii) identify which ecological strategies have been most successful in the face of global change and (iii) evaluate the efficacy of the protected areas network for safeguarding plant communities of coastal dunes. We compiled 2583 geo-located vegetation relevés spanning over half a century and covering the entire length of Italy's sandy coastline. Using this data base, we developed statistical models to test whether the vegetation cover of both individual species and habitats has changed over time. We then tested whether species-level changes in vegetation cover through time could be explained by species' functional traits and ecological strategy. Finally, we assessed the efficacy of current conservation measures by exploring how vegetation cover responded following the expansion of the protected areas network. Our results indicate that, where protected, plant communities have generally increased in vegetation cover in recent years. The strongest increase in cover occurred in the wooded dune habitats, where late-successional, tall-growing and large-seeded species show the clearest signs of recovery. However, this has come in part at the expense of dune grasslands, which thrive under natural disturbance and have declined since the 1960s. The Natura 2000 network seems to have played a central role in this recovery process, as the cumulative coastal land area under protection has tripled since the network was first established. Synthesis and applications. Our results suggest that protected areas can play an important role in safeguarding coastal dune plant communities against land-use transformations. In this context, functional traits can be a powerful tool in guiding conservation planning, helping to identify groups of species most at risk of population declines. Nonetheless, future conservation interventions need to be mindful to ensure that the natural disturbance regime of dune ecosystems is not disrupted.