The canopy cover of trees plays an important role in arid and semi-arid ecosystem. This research investigated the canopy effects of individual Ziziphus species (Z. spina-christi (L.) and Z. nummularia (Burm.f.)) on soil biological and physicochemical properties in the arid environment. Soil samples were collected from three positions (mid-canopy, canopy edge, and 2 m beyond the canopy (control)) at 0–20 cm depth during spring, across two slope classes (< 10% and > 25%). We analyzed physical (bulk density, saturated moisture content, soil texture, gravel %), chemical (pH, EC, organic matter (OM), total nitrogen (TN), phosphorus, potassium and lime %) and biological (basal respiration (BR), substrate-induced respiration (SIR), microbial biomass carbon (MBC), urease and alkaline phosphatase activity. The results revealed that bulk density and EC increased with distance from the tree, while OM, TN and biological properties (BR, SIR and MBC) significantly decreased. Furthermore, analysis revealed that the highest activity of urease enzyme (11.81 μg NH4Nml-5dwt 2h⁻1) and alkaline phosphatase (1023.59 μg pNP g⁻1dm h⁻1) was recorded in the rhizosphere of Z. nummularia. The results also showed that soil chemical, biological and enzymatic properties were higher values gentle slopes (< 10%) compared to steeper slopes (> 25%). These findings demonstrate that tree cover play a crucial role in enhancing soil quality in arid ecosystems. Moreover, the improvement varies significantly depending on both vegetation presence/absence and species identity. Therefore, for effective soil restoration and management in these vulnerable ecosystems, careful selection of appropriate species, particularly native taxa, is critical.
