engleski

Xerothermic cliff vegetation of the central Mediterranean basin

The xerothermic cliff vegetation of the western Mediterranean was originally included in the order Asplenietalia glandulosi, of the Asplenietea trichomanis class. Subsequently, due to the high regional diversification characterizing this vegetation type, other orders and numerous alliances have been proposed for the Mediterranean Basin. However, the floristic, synchorological and syntaxonomic relationships among these syntaxa were in most cases based on expert judgement and this led to different and sometimes contrasting interpretations. This situation is more accentuated in the central part of the Mediterranean, that is at the crossroad between eastern and western floristic elements and syntaxonomic units. The aim of this work is to revise the xerothermic cliff vegetation of the central part of the Mediterranean Basin, from France to Greece, in order to define the syntaxonomic and synchorological pattern and identify the diagnostic species of the high- rank syntaxa under a supranational perspective. The revision was based on a data set of nearly 1250 phytosociological relevés. The relevés were hierarchical clustered (flexible beta method, with Bray- Curtis coefficient), involving several data transformations. The dendrogram was interpreted from a syntaxonomic point of view, using nomenclatural type relevés as a basis. Indicator Species Analysis was used to identify the diagnostic taxa of the main syntaxonomic units (orders and alliances) and NMDS ordination was used to visualize the floristic and chorological relationships among syntaxa. Results showed three main clusters of relevés representing the chasmophytic vegetation of southern France and western Italy (Asplenietalia glandulosi, with 5 alliances), Adriatic area (Centaureo- Campanuletalia, with 4 alliances) and Southern Balkans (Onosmetalia frutescentis, provisionally with only 1 alliance). The Asplenietalia glandulosi turned out to be characterized by a north-south differentiation that was represented by two subordinated syntaxonomic units: Asplenienalia glandulosi and Tinguarrenalia siculae. The new proposed syntaxonomic scheme provides an overview of the cliff vegetation of the central part of the Mediterranean Basin. This scheme mostly matches the one provided with the EuroVegChecklist, but exhibits also important differences concerning the syntaxonomic position of some alliances (Dianthion rupicolae, Centaureion pentadactyli, Arenarion bertolonii, and Caro- Aurinion), and defines the floristic and chorological relationships among high-rank syntaxa, with new revised sets of diagnostic taxa. This revision might be useful for further detailed phytosociological works.

Asplenietalia glandulosi ; Centaureo-Campanuletalia ; Classification of vegetation ; Indicator Species Analysis ; Mediterranean cliff vegetation ; Onosmetalia frutescentis

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