The vegetation of S'Ena Arrubia lagoon(centre-western Sardinia)

This study describes the vegetation of S’Ena Arrubia lagoon, in the Gulf of Oristano, in the centre-western coast of Sardinia. This lagoon is classified as: Special Protection Zone (S.P.Z.) according to EEC Directive 79/409, community importance site according to EEC Directive 92/43, I.B.A. (Important Birds Area) site and fixed oasis of fauna protection and natural reserve. Throughout the years it was subject to several alterations. The most important ones were carried out in the Seventies and allowed the marine water upwelling and the fast removal of freshwater coming from the watershed. Before the fulfilment of these interventions, lagoon waters had a low salinity, as demonstrated by previous vegetation studies that showed the presence of freshwater communities and, only to a smaller extent, of halo-tolerant and halophile ones. This phytosociologic study led to the identification of several associations that are showed in the groups of merely halophile vegetation, in the freshwater and subhalophile lagoon vegetation and in the merely anthropogen vegetation typologies. The location of the considered typologies is represented with distributive patterns, which synthesise the current state of vegetation referring to the salinity. Two new associations, the Inulo crithmoidis-Paspaletum vaginati and the Astero tripolii-Bolboschoenetum maritimi, are here described. The first is dominated by the presence of Paspalum vaginatum Swartz, recorded for the second time in Italy and for the first time in Sardinia. It is recorded near the inlet, where it forms mosaics together with Salicornietum emerici association and it is also present, as bolboschoenetosum maritimi subassociation, in more inland and less salty zones. The latter new association includes the subhalophile reedswamps that are present in the areas flooded by salty waters for a long time, where it replaces the Scirpetum compacto-littoralis, a less halophile association present in several sites of the Mediterranean and also in Sardinia. In addition, it is necessary to point out the recovery of Salicornietum venetae association, characterised by the presence of Salicornia veneta, which was believed endemic in the North Adriatic lagoons. Finally, the significance of environmental changes fulfilled in the basin, which are the reason for some vegetation modifications and are detected by comparison between current associations and those at the beginning of the Seventies, is pointed out.