STUDY OF PLANT DIVERSITY IN THE RANGELANDS OF STIPA TENACISSIMA L.: CASE OF SFISSIFA AND EL BIODH REGION (SOUTH WEST ALGERIA)

The floristic diversity analysis made it possible to distinguish 42 species listed in 30 genera and 17 families in the Sfissifa station and 34 species classified in 23 genera and 15 botanical families in the El Biodh station. The most representative families in the Sifissifa station are: Asteraceae (14,28 %), Amaranthaceae (11,90 %), Brassicaceae (11,90 %), Poaceae (7,14 %), Lamiaceae (7,14 %) and Cistaceae (7,14 %). The dominant families in El Biodh station are Asteraceae (17,64 %), Poaceae (11,74 %), Amaranthaceae (8,82 %), Brassicaceae (8,82 %), Lamiaceae (8,82 %) and Cistaceae (8,82 %). The other remaining families have only one or two species with estimated rates ranging from 2,38 % to 4,76% in Sfissifa and 2,94 % to 5,88 % in El Biodh. The study of biological types shows the abundance of therophytes in the two stations with 42.86 % at Sfissifa and 50 % at El Biodh, which reflects the importance of the anthropologic action and the xericity of the climate. The analysis of the biogeographical spectrum shows the dominance of native species of the Mediterranean (19 species in Sfissifa and 15 species in El Biodh). The AHC analysis of the data revealed the main factors controlling the distribution of plant formations in the two studied stations including overgrazing, salinity and desertification. The combination of prolonged droughts and anthropogenic pressures exerted on the studied areas results in the extension of species of low pastoral value and the appearance of vast expanses of bare soil reaching the stage of desertification.