Vegetazione e paesaggio vegetale dell'arcipelago di La Maddalena (Sardegna nord-orientale)

We present here a phytosociological study of the vegetation and plant landscape of the La Maddalena archipelago, which is situated in the Bocche di Bonifacio, between north-eastern Sardinia and southern Corsica. The lithological substratum of the archipelago is mainly made up of granite from plutonic intrusions, of the Superior Permian Carboniferous period. The area is part of the Mediterranean macrobioclimate, pluviseasonal-oceanic bioclimate, upper thermomediterranean thermotype, low dry ombrotype. On the basis of published data, the flora of the archipelago includes 986 taxa, of which 51 are endemic. The dominant life form is of therophytes, which represent around 50% in all.The plant communities identified through the phytosociological analyses are presented in groups according to their ecological and structural characteristics. Moreover, these communities are presented in an overall syntaxonomic scheme. Twenty new associations are described:Agrostio stoloniferae- Cyperetum badii, Alismo lanceolatae-Gratioletum officinalis, Allio commutati-Lavateretum arborae, Anthoxanto aristati-Agrostietum salmanticae, Apio crassipi-Isoetetum tigulianae, Arenario balearicae-Menthetum requienii, Baldellio ranunculoidis-Eleocharitetum palustris, Bellio bellidioidis- Arenarietum balearicae, Callitrico stagnalis-Glycerietum spicatae, Catapodio marini-Silenetum beguinotii, Exaculo pusilli-Lythretum portulae, Isoeto istrici-Montietum amporitanae, Junco acuti-Oenanthetum crocatae, Myrto communis-Salicetum atrocinereae, Polypogono subspathacei- Parapholidetum filiformis, Romuleo requienii-Bellidetum bellidiodis, Romuleo requienii-Colchicetum corsicae, Rubo ulmifolii-Myrtetum communis, Salicornio patulae-Crypsidetum aculeatae, Sileno nummicae-Malcomietum ramosissimae.The interpretation of the dynamic relationships between the plant communities has allowed seven vegetation series to be recognised: two climatophilous (Prasio majoris-Querco ilicis Σ phillyreetosum angustifoliaeandGalio scabri-Querco suberis Σ quercetosum suberis), two edaphoxerophilous (Erico arboreae-Junipero turbinatae ΣandOleo sylvestris-Junipero turbinatae Σ), one edaphohygrophilous (Oleo sylvestris-Junipero turbinatae Σ), one riparian (Populo albi Σ) and one marshy (Myrto communis-Salicio atrocinereae Σ).The landscape units (geosigmeta) have been identified through the integration of the vegetation series with the environmental factors. Since the territory has geological and bioclimatic characteristics that are fairly uniform, the resulting vegetal landscape can be included mainly in the Holm oak series geosigmetum (Prasio majoris-Querco ilicis Σ phyllireetosum angustifoliae), and to a minimal extent in the Cork oak seriesgeosigmetum(Galio scabri-Querco suberis Σ quercetosum suberis).However, this uniformity is only apparent, since by passing to a greater level of detail, the analyses have allowed a high degree of phytocoenotic biodiversity to be revealed, linked to the micromorphological, microedaphic and microclimatic variations (microgeosigmeta). Among these very particular microenvironments there are, for example, those that can be found inside the tafonies, in the rock fissures, in the temporary ponds, in the fragile sand ecosystems and in the therophytic grasslands, where there are communities characterised by endemic species and with an ecology often defined by intermediate conditions of microecotonal character.The problems concerning the management of the plant landscape are stressed in the conclusions from the point of view of a management model that guarantees the conservation of the natural resources in a way that is compatible with the socio-economic development of the territory and its potential for exploitation.