Plant diversity and relationships with environmental factors after rangeland exclosure in arid Tunisia

On a broad scale, the extent of clearing and plowing of the crops in rangelands has brought a significant degradation in pasture species along with an invasion of weed species. This work evaluates the vegetation composition of an agriculture field after 15 years of exclosure and protection against clearing and plowing activities. Vegetation cover, density, richness, species dispersion, and diversity index were estimated through 12 permanent transects of 20 m in length and 23 quadrats of 1 m(2) over a 3-year period. Species diversity and its relationship with environmental factors (soil, canopy, elevation, and road effect) were analyzed by canonical correlation analysis. About 72 species were recorded across the study area. Plant species encountered were divided into three communities of steppic (45.8%), weed (44.4%), and steppic-weed (8.4%), with 1 cultivated species (1.4%). Raunkiaer classification showed a dominance of therophytes (73.6%) over the other groups. This work showed that exclosure of degraded arid lands can regenerate 16.6% of perennial plant cover that allowed to classify the experimental field as a low degraded zone.