Spatial connectivity and boundary patterns in coastal dune vegetation in the Circeo National Park, Central Italy

Distribution patterns of coastal sand dune plant communities in the Circeo National Park (Central Italy) are quantified and compared by measuring spatial connectivity and richness of community boundaries along the dune profile. The purpose of this study is: (1) to evaluate patchiness and frequency of spatial links between communities; (2) to identify the communities most sensitive to disturbance; and (3) to predict probable changes due to modification of spatial zonation. Data were obtained using belt transects across the Holocene coastal dune zone. Vegetation zonation from the seashore to the foredune slacks is analysed in relation to chorological, phytosociological and life-form types. We found that under relatively undisturbed environmental conditions communities formed a sequence (communities I to 7), with the exception of a replacement community, which occupied gaps in the perennial vegetation. The spatial distribution of some communities was reduced as a consequence of disturbance; others became fragmented in small patches or even disappeared. In coastal environments with strong, complex gradients, the existence of certain communities depends on specific links (neighbourhood effects) and high connectivity values do not indicate better conservation conditions.