Effect of two species of Prosopis (P. cineraria and P. juliflora ) on soil quality in Saharo-Sindian region of Iran (Case study: Sistan and Baluchestan province)

The purpose of this research is to evaluate and compare the effects of two native and non-native species of Prosopis (Prosopis cineraria and P. juliflora) on the physical, chemical, and biological characteristics of soil in Sistan and Baluchistan province in Iran. For sampling, 30 trees from each species were selected, and soil samples were taken from a depth of 0-30 cm both under and outside their canopy. After combining all 5 soil samples for each species, samples were obtained for laboratory analysis. Soil properties such as saturated moisture (SM), pH, electrical conductivity (EC), organic carbon (OC), total nitrogen (TN), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), microbial respiration (SMR), substrate-induced respiration (SIR), microbial biomass carbon (MBC), nitrification potential (PN), as well as urease, dehydrogenase, alkaline phosphatase, and acid phosphatase enzyme activity were measured in the laboratory. Based on these measurements, a soil quality index was calculated. The results significantly showed that the highest values of SM, TN, SIR, and dehydrogenase enzyme were found under the canopy of P. cineraria, while the highest values of Mg, P, TN, and acid phosphatase enzymes were observed under the canopy of P. juliflora species. The lowest values of these parameters were observed outside the canopy of both species. The soil quality index indicates that soil quality under the P. cineraria tree is higher than under the P. juliflora tree and outside the crown canopy of both species. The conclusion suggests that native Prosopis tree species improve soil fertility and acidity, with soil quality under their canopy being numerically higher than under non-native Prosopis. Therefore, preserving natural forests of P. cineraria species and afforestation with it are recommended to maintain and improve soil quality in Sistan and Baluchestan province.