PJB-2022-42
Using exotic shrubs as a restoration tool in Tunisian arid areas: effects on understorey vegetation and soil nutrients
Imed Mezghani
Abstract
In the semiarid areas of the Mediterranean basin, restoration activities during the XXth century have mainly relied on extensive plantations of Acacia salicina, which now cover thousands of hectares. Here we checked the effects of exotic and native planted shrubs (Acacia salicina and Retama raetam, respectively) on the understory vegetation and soil properties. For each shrub species, two sub-habitats were distinguished: the canopied sub-habitat and the un-canopied sub-habitat (open grassland). Soil moisture was measured in both sub-habitats at 10 cm depth. We investigated the effect of shrub species on soil fertility. Soil samples were collected from the upper 10 cm soil, excluding litter and stones. For vegetation structure, we determined aboveground biomass, species density, species richness. The nutrient status of soil (organic matter, total N, extractable P) was found to be significantly higher under shrubs and open areas. This tendency remained constant with the soil water content which was significantly higher under shrubs compared to open sub-habitats. For water content, there were no significant differences between studied shrubs. Aboveground biomass, species richness and the density of perennial species were significantly higher under the shrub species compared to other sub-habitats. Among the two studied shrubs species, Retama raetam had the strongest positive effect, but without significant differences, on the understory vegetation. In this context, exotic shrubs can be used as a candidate shrubs in different programs of restoration tool in arid areas and more suitable to create islands of resources and foster succession than the other investigated tree species.
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