Soil physicochemical and biological properties of Christ's thorn (Ziziphus spina-christi L.) in the Izeh

Since the long-term sustainability of the natural ecosystem depends on soil quality protection, knowledge about soil conditions in natural lands is effective for their correct management. The aim of this study was to investigate the impact of Christ's thorn (Ziziphus spina-christi L.) crown on soil physicochemical and biological characteristics in the Izeh region of Khuzestan province. Soil sampling was carried out from the soil surface (0-20 cm) under the crown and open area (control) by using random transects. In addition, several numbers of soil physical (bulk density, and saturation moisture), chemical (acidity, organic carbon, potassium, and phosphorous) and biological (carbon microbial biomass, basal respiration, and microbial quotient) properties were measured. According to the result, the organic carbon content under the crown was 1.90 percent, which was 23.5% higher than that of the soil outside the crown. The available soil potassium content (233.35 mg kg-1) under Christ's thorn crown was higher than that of open area. However, pH was not shown to be affected by trees, with no significant difference between measured values in free space and under the crown. The highest amounts of carbon and nitrogen microbial biomass (547 and 60.1 mg kg-1, respectively) were found under the canopy. In addition, the highest basal respiration rate was 19.29 mg of carbon dioxide per kg of soil under the tree crown. The microbial quotient of 1.68% was highest under the crown. Based on the results, the metabolic rate showed an inverse trend, with the highest amount was observed outside the tree shadow. Furthermore, the presence of Christ's thorn trees in the study area has resulted in increasing soil fertility and the improvement of soil microbial activities.