The Effects of Drought on Plant Communities in the Desert Rangelands of Tunisia

Abstract

Plant communities of the Dahar plateau are characteristic of the Tunisian desert both in structure and in dynamics. Although a number of plant communities can be differentiated, four major vegetation types are often distinguished that differ in plant species cover and composition, as well as other factors, such as soil types and elevation. Among the abiotic factors which affect the vegetation structure and diversity of plants, climate is probably the most relevant. The desert vegetation in southern Tunisia is in a state of change and the most debilitating risk is that of drought in these desert areas. Under protection from grazing the dynamic nature of this vegetation is affected by such conditions such as drought. Precipitation probably explains part of the vegetation response to drought. The effects of drought stress on vegetation were tested for four plant communities who are Stipagrostis pungens, Anthyllis sericea, Helianthemum kahiricum, and Hammada schmittiana. Patterns of plant response to drought differed among the four vegetation types considered. Vegetation cover, species richness, and diversity were used for the characterization of the considered vegetation. Main results show that plant cover, richness, and diversity change with vegetation type and rainfall variations. Vegetation cover on H. kahiricum steppe is more affected by drought than the other steppes. Plant diversity is affected by drought in all plant community and mainly on the A. sericea and H. kahiricum steppes.