Human trampling effects on Mediterranean coastal dune plants

"Coastal habitats are particularly vulnerable to recreational impacts because these environments are highly dynamic and continually change in response to biotic and abiotic factors. Sand dune communities are worldwide characterized by high levels of biodiversity, but are often affected by human induced impacts as those caused by tourist trampling. To understand the effects of human frequentation, trampling, and other human induced impacts, fencing experiments have been traditionally carried out on coastal dunes. Since in touristic areas dune systems are subjected to different intensities of human frequentations rather than to opening or fencing, in this paper we explore the effects of accessibility on vascular plants cover. This study tests the hypothesis that human frequentation on beaches affects spatio-temporal variability of vascular plant abundance on dunes by comparing plant assemblages of high and low accessible sites in NE Sardinia (Italy). Our results show that accessibility plays a crucial role in conditioning the percentage of vegetation cover in Mediterranean dunes. In fact, not only we found a perennial vegetation cover that was significantly higher in the sites with low accessibility (and consequently low frequentation), but we also showed that at the sites with high accessibility there were significant differences in vegetation cover between times of sampling (cover was higher before than after summer): on the contrary, differences in perennial vegetation cover among times were not significant at the low frequentation sites. After summer the difference among low and high frequentation sites in species composition and cover was > 90%.. Multivariate analysis identified those species that play a pivotal role in differentiating the low and the high frequentation sites. Among them, Crucianella maritima and Sporobolus virginicus can be considered as differential species. Overall, our data show vegetation and plant species responses to human induced impacts, and are therefore important to support conservation actions in Mediterranean coastal areas interested by mass tourism.. "