Laboratoire d'ecologie alpine

Coastal dune systems are particularly fragile and threatened environments, which, however, provide fundamental ecosystem services to nearby urban areas acting for example as protective buffers against erosion. Correctly assessing their conservation status is a priority in order to manage them adequately and to plan urban development in coastal regions. In this paper we propose a practical multiscale method for the assessment of the conservation status of sandy coastal environment. The proposed method is articulated in two stages, one focusing on the landscape and the other on the plant community level. In the first phase mosaic structure and composition of the coastal landscape are analyzed using a series of indicators: natural coastal surface, richness of land cover typologies, landscape diversity and eveness, number and average size of habitat patches, and mean shape index. At a detailed scale, floristic, vegetational and structural aspects of the dune plant communities are analyzed along the main environmental gradient by measuring: spatial connectivity and richness of boundaries, species diversity, eveness and chorological index. In this work we apply and test the method in an experimental area on the Tyrrhenian coast of Italy (Latium region), comparing the conservation status of two study sites.

Question: We investigated the spatial pattern of coastal landscapes invaded by iceplant (Carpobrotus aff. acinaciformis) focusing on two questions: (1) Does the spatial structure of iceplant patches differ from that of native natural costal dune cover types?; (2) Is the distribution of iceplant patches related to other cover types?Location: Tyrrhenian coast of Central Italy.Method: On the basis of a detailed land-cover map, we calculated structural metrics for iceplant patches and for each native coastal dune cover category (mean patch size and patch shape index) and compared them by means of anova. To assess the spatial association between iceplant patches and the different cover types, we implemented an electivity analysis which analyses the frequency of common borders.Results: The mapped coastal dune cover types included beaches, dunes and sand plain variants, related to the typical Tyrrhenian coastal dune vegetation zonation. Iceplant-dominated vegetation presented elongated and irregularly shaped patches, which were not significantly different from most of the natural cover types suggesting a natural spread along the territory analysed. Iceplant patches were positively associated with beach, mobile and inter-dune cover types indicating that these habitats are exposed to further alien spread. Iceplant patches were also positively associated with artificial surfaces highlighting this cover type as a possible source of propagule pressure.Conclusions: The proposed landscape approach combining patch-based metrics with edge-based metrics provided a comprehensive description of the invaded coastal landscape. From an applied research perspective, this landscape approach could be useful in identifying the correct management strategies for alien-invaded areas.