PLANT LANDSCAPE OF RAS DIMAS PENINSULA (GOVERNATORATE OF MONASTIR, CENTRAL COASTAL TUNISIA)

Abstract

The Ras Dimas lagoon lies along the coast of Central Tunisia (35°37'45.84"N, 11° 2'44.61"E), in the region of Sahel, about 20 km linear distance to the south from Monastir and about 160 km from Tunisi. The lagoon is made up by a sandy peninsula with white sands rich in limestone with fine granulometry, about 3 km long, up to 200 m wide and up to 2 m high, that contains about 120 hectares of sea. Previously this peninsula was regularly isolated from the continent forming the island of Edzira, in the last years, sea storms and the different streams course, likely caused by the restructuring of the Port of Bekalta, has given the actual configuration of a peninsula. In April 2013, as part of the Initiative PIM, a scientific mission, initially planned in the Island of Kuriat, has been moved to the coast of central Tunisia due to bad weather conditions. This shift made possible the floristic survey of areas with great naturalistic value, still not well floristically known. During this mission, phytosociological relevés have been taken and herbarium specimens have been collected and stored in the Herbarium Mediterraneum Panormitanum (PAL); plant identification has been done with the help of the Flora of Italy (1) and of Tunisia (2, 3) and by direct comparison with the exsiccata housed in PAL. The distribution of taxa and phytocoenoses resulted to be influenced by elevation and distance from the sea shore. The studied vegetation is characterized by psammophilous and halophytic communities. Flat areas near the sea are colonized by communities referable to the class Cakiletea maritimae, followed inwards by a belt of embryo dunes that houses perennial rhizomatous Poaceae characterizing the class Ammophiletea and related syntaxa. The flat, periodically flooded, areas behind the dunes are dominated by Juncus maritimus Lam., in contact with saltmarshes dominated by Sarcocornia perennis (Mill.) A.J. Scott (classes Juncetea maritimi and Sarcocornietea fruticosae, respectively).Where the altitude is some decimetres a.s.l., a more mature vegetation dominated by small cushion shaped chamaephytes belonging to Crucianelletalia maritimae. Near the inner part of the lagoon, where the elevation is a bit higher (some dm a.s.l.), there is a grassland of Lygeum spartum L. On the inner, on stabilized dunes, there are few remnants of a psammophilous maquis dominated by Retama retam subsp. bovei (Spach) Talavera & Gibbs, ascribed to the class Quercetea ilicis (Oleo-Ceratonion). Taxa of particular biogeographic interest found in the surveyed area are: Anagallis monellii L., Echiochilon fruticosum Desf., Helianthemum stipulatum (Forssk.) C. Chr., Linaria aegyptiaca (L.) Dumort., Silene succulenta Forssk. and Stachys arenaria Vahl. Cuscuta palaestina Boiss. subsp. palaestina and Carduus argyroa Biv. are here reported for the second time from Tunisia (4, 5). The exploration of the peninsula of Ras Dimas, allowed us to collect and study many taxa and to gather an unprecedented herbarium and photographic documentation of the flora and plant communities. Further research is aimed, that will provide new data also in comparison with the previous vegetation cover of the area.