The results of observations and measurements on five units of steppic vegetation in the mediterranean arid zone of S. Tunisia are presented in this paper. These units were totally protected against big herbivore grazing using barbed wire fencing during seven consecutive years.
The steppes in question are composed of small shrublike chamaephytes. Annual plants appear when there is sufficient rainfall. This vegetation has been subjected to extensive overgrazing and is in general, degraded.
Our objective was to study regeneration of the natural vegetation of five steppe types in order to recommend an optimum period for protection:
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a steppe on a gypseous crust resulting from overgrazing of the Zygophyllum album -Anarrhinum brevifolium association;
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a steppe on a sandy, gypseous, rocky-surfaced colluvium resulting from overgrazing of the Rhantherium suaveolens-Artemisia campestris association, Atratylis serratuloides sub-association;
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a very open steppe on a deep, gypseous, sandy colluvfum-alluvium (sierozem) having the appearance of a post-cultivated grazed Plantago albicans facies of the Rhantherium suaveolens association; 4) a steppe in good condition on a deep, sandy-soiled plain representative of the Rhantherium suaveolens -Artemisia campestris association; 5) a post-cultivated facies of the Artemisia herba-alba -Arthrophytum scoparium association on a deep piedmont, loamy, and gypseous colluvium soil, traditionally cultivated with cereals.
The effect of protecting these steppes was mainly the increase in cover of the perennial species. The cover of the steppe vegetation on sandy soils increased more than that of the steppes on loamy or gypseous crusts; this must be taken into consideration for pastoral management. The results also show that a protection period of 7 yr is not sufficient in an arid zone for new species to appear nor for succession to reach a next stage. * Nomenclature follows Quezel & Santa (1962) in 'Nouvc!le Flore de l'Alg6rie et des r+gions d6sertiques rn6ridionales'. For typical Tunisian species, the authors are cited.