Diversité biologique et phytogéographique pour des niveaux différents de salinité dans la région du Chott-Ech-Chergui (Sud-Ouest de l’Algérie)

Abstract

Biological and phytogeographical diversity for different levels of salinity in the region of Chott-Ech-Chergui (South-West of Algeria). The Algerian halophilic areas have been subject to few studies, which remain fragmented. If their floristic, pedological and phytogeographical characterization begins to be better clarified, studies related to changes in the flora and vegetation along a salinity gradient are, however, much rarer. The aim of this present work was to survey, at least partly, such changes in one of the largest saline lakes in Algeria known as the Chott-Ech-Chergui. The a priori surprising results are interesting because they show that, regardless of vegetation type and salinity degree, diversity indices are relatively high. They have the same value, when not larger, as their counterparts in steppe and unsalted presaharan areas. This contrasts with the obvious homogeneity of the landscape dominated by chamaephytes. In reality, it appears that conventional indices such as the Shannon index show here a limit in the conditions of their application. This peculiarity, although known, is rarely mentioned in the scientific literature. The evocation of this methodological problem reinforces the interest of the present work.