Influence of grazing on structure, composition and dynamics of vegetation in Mediterranean temporary pools (northern Tunisia)

Three temporary pools of Scjenane region (northern Tunisia) have been studied with the aims of characterizing their vegetation, and of specifying the impact of grazing on their structure, composition and dynamics. Permanent transects of quadrats have been surveyed in spring and summer during two (not-grazed pool) to three years (grazed pools). The vegetation of the three pools is organized in three concentric belts related to the topographic gradient. The between-years dynamics is strongly characterized by the alternation of distinct spring and summer vegetations. Grazing appears as the main control of the composition and structure of hydrophytic plant communities. It prevents the colonization by competitive, perturbation-sensitive species, and favours the persistence of annual, light-demanding dwarf plants. In order to protect the biodivcrsity of these rare habitats in Tunisia, it is necessary to maintain, through an adapted management of grazing, a landscape mosaic of grazed and not-grazed zones