干旱区生态环境知识资源中心

The present study was conducted in the Bouhedma national park and its surroundings, located in the arid area of Tunisia and considered a Biosphere reserve by UNESCO in 1977; it is a protected area with special ecological characteristics and an important dynamics of space occupation. The park contains the only wooded steppe with Acacia tortilis (Forsk.) Hayne subsp raddiana (Savi.) Brenan var. raddiana Brenan in Tunisia. With the aim of safeguarding and management of the park, a better knowledge of the distribution patterns and dynamics of the vegetation of this zone makes it possible to consider programmes of restoration and sustainable management of the natural environment. Based on the interpretation of remote sensing data and use of SIG, the study was devoted to the elaboration of charts relating to the ecological systems present in 2005, and to the distribution of the steppe with Acacia tortilis according to physical factors such as slope, altitude, type and depth of the soil. Also, the production of seeds was studied to explain the effect of physical factors on the regeneration of the species. The analysis of soil occupation dynamics translates into a good distribution (7056 ha) of steppe with Acacia tortilis. The study shows that Acacia tortilis is located on 6242 ha at an altitude of 20 m to 150 m and on 814 ha at an altitude from 150 to 250 m. This species grows on 5815 ha with a weak slope (0 to 3 %), on 928 ha with a slope of 3 to 5 % and only on 313 ha with a slope > 5 %. The results show that the Acacia tortilis is regenerated on the not very advanced soil of hydrous contribution with a surface of 3832 ha, on rendzina with 1280 ha, the isohumic soil with a surface of 986 ha. Acacia tortilis colonizes the far from deep soil with a surface of 2796 ha, the fairly deep soil with a surface of 2175, the very deep soil with a surface of 1970 ha, the not very deep soil with a surface of 75 ha and the deep soil with a surface of 40 ha.