Changes in Physical and Chemical Soil Properties under the Influence of the Rhizosphere and Canopy of Wild Almond Trees (Amygdalus arabica Olive.) with Different Ages

In arid and semi-arid ecosystems, isolated trees significantly influence the soil properties and can have a great impact on the soil fertility as well as the conservation and improvement of soil quality. This investigation was conducted to examine the influence of wild almond (Amygdalus arabica Olive.) trees having different ages on the physical and chemical soil properties. Soil samples were taken from the depths of 0-20, 40-60, 80-100 and 120-140 cm at two distances from the tree crown including the basal area (referred to as the rhizosphere) and the canopy edge in 3 replications for the 30, 50, and 130 year-old stands and also, in a control site, all in the Anjarak area, southeast of Baft city, Kerman Province. Soil properties including pH, EC, organic matter, calcium carbonate equivalent, available and non-exchangeable potassium and soil texture were measured in all samples. The results indicated that the measured soil properties in different depths in the study area had been influenced by the age and the canopy size of the wild almond trees. The highest and the lowest amount of pH were found in the control soil and the soils covered by 130 year-old trees, respectively. Besides, the electrical conductivity of the soil under the tree crown was more than that of the soil in the canopy edge. The accumulation of C, N, and other nutrients under the tree canopies resulted in the creation of fertility islands surrounding the trees. Furthermore, the soil physical and chemical properties were greatly improved with the increase in the tree age of Amygdalus arabica Olive. As the conclusion, wild almond trees could have very positive effects on soil properties. Therefore, it is essential to protect the trees. Otherwise, the risk of soil quality reduction would be increased and soils might become more susceptible to soil erosion.