The Effects of Mesquite (Prosopis juliflora) on Soils and Plant Communities in the Deserted Rangelands of Bahrain

The influence of mesquite trees (Prosopis juliflora (Swartz) D.C.) on the physicochemical properties of soils and annual understory plants was investigated in the deserted rangelands of Bahrain. Soil properties were measured in the understory and the uncanopied adjacent areas of mesquite trees. Likewise, the number of plant species was assessed in four 1 × 1 m randomly distributed quadrates in the understory and the uncanopied adjacent areas. The results showed that sand particles exceed 96% of soil composition. Soil bulk density at the 0–5 cm soil depth was significantly higher in the understory of trees compared to the uncanopied adjacent areas. However, moisture at a depth of 40–60 cm was significantly higher in the uncanopied adjacent areas. No differences in the pH, EC, K, Na, and Ca were found between understory and the uncanopied areas in all soil depths. Levels of N, P, Mg, and organic matter were significantly higher in the understory of trees compared to the uncanopied adjacent areas. Organic matter was twice the amount in the upper 20 cm of soil layers in the understory of mesquite trees. Species richness did not differ between the understory and the uncanopied areas. Nevertheless, the density of ephemerals in the understory of mesquite trees was higher than the uncanopied areas by 18%. The Shannon-Weaver index of diversity was higher in the uncanopied areas compared to the understory. The study concluded that the canopy effects of mesquite trees on soil vary with depth. Nonetheless, the influence of mesquite on flora could be beneficial for annual understory plants but subject to many operating factors, including density and cover of mesquite trees.