Changes in Some Physical and Chemical Properties of Soil under the Canopy of Wild Pistachio (Pistacia atlantica Desf) Plant (Case Study: Farak, Tafresh, Markazi Province)

Background and Objectives
Soil, as one of the pillars of ecosystems, plays a major role in the creation, change, and diversity of forest species. On the other hand, plant growth also plays an important role on changes in physical, chemical, and biological properties of soils. Soil, one of the most important components of the forest ecosystem, plays a decisive role in the cycle of materials, fertility, and sustainability of ecosystems. At the same time, vegetation, especially tree species, can affect soil properties through biological and chemical processes such as leaf litter, root secretions, and selective absorption of elements. In the arid and semi-arid regions of Iran, the forests of the Irano-Turanian region, despite climatic limitations, have the presence of species such as the sedge, which have high ecological stability. The species of Pistacia atlantica Desf, with an area of ​​about 2.4 million hectares in Iran, plays an important role in soil stabilization, carbon storage, and biodiversity conservation. However, there is limited information on the impact of this native species on soil properties-especially at the level of physical and chemical parameters. Some studies have shown that in arid regions, tree species have a greater impact on soil biological indices, while changes in physical and chemical properties are less pronounced. In recent years, there has been increasing attention to the role of native tree species in soil changes, especially in arid and semi-arid ecosystems. These studies show that vegetation is not only affected by soil, but also plays an active role in ecosystem formation by changing soil properties, nutrient cycling, and microbial activity. To monitor changes in soil, it is necessary to conduct periodic measurements in fixed sample plots of tree species.
 
Materials and Methods
In this project, the soil samples were collected from a one-hectare sample plot in Markazi province of the protected habitat of the Irano-Turanian species of the Pistacia atlantica Desf. This study was conducted to investigate the effect of the Pistacia atlantica Desf on the physical and chemical properties of the soil in the Farak habitat, Tafresh, Markazi province, Iran. In a one-hectare sample plot, 15 soil samples were taken from below of the canopy of the Pistacia atlantica Desf trees and 15 samples from outside the canopy (control) at a depth of 0–15 cm and were combined into 5 composite samples. The soil physical and chemical analyses were performed including texture, bulk density, pH, electrical conductivity (EC), calcium carbonate equivalent, organic carbon, total nitrogen, and available- phosphorus, potassium, calcium, magnesium, sodium, iron, manganese, copper,  and zinc.

Results
The results of variance analysis showed that the Pistacia atlantica Desf plant had significant effects only on available- phosphorus (p<0.01), zinc (p<0.01), magnesium (p<0.01), calcium (p<0.05), and sodium (p<0.05). While other parameters including texture, bulk density, pH, EC, organic carbon, total nitrogen, calcium carbonate equivalent, and available- potassium, iron, copper, and manganese did not show any statistically significant differences. These findings indicated that the Pistacia atlantica Desf tree has a limited effect on the physical and chemical properties of the soil in the studied time-space period and is mainly effective on the selective absorption of some mineral elements.
 
Conclusion
These findings indicated that the Pistacia atlantica Desf tree in arid ecosystems acts more as a selective consumer of mineral elements than as an overall modifier of soil quality. Therefore, for a comprehensive assessment of the effect of tree species in arid areas, in addition to chemical parameters, biological indicators of the soil should also be considered. In most cases, the Pistacia atlantica Desf tree decreased the percentage of organic carbon and total nitrogen, electrical conductivity, and available phosphorus as well as the percentage of soil sand and silt particles, while this tree increased the percentage of clay, and available- potassium, iron, and manganese and had no significant effect on the soil pH. By having physical and chemical parameters of the soil, as a knowledge-based approach with accessibility and flexibility, more information can be provided to experts and operators for decision-making on improving soil fertility and managing Pistacia atlantica Desf tree nutrition.
Author Contributions

Moradinejad and M. Matinizadeh conceived and planned the experiments. A. Moradinejad analyzed data and wrote the first manuscript. All authors contributed to the interpretation of the results. All authors provided critical feedback and helped shape the research, analysis and manuscript.

 
Data Availability Statement
Data available on request from the authors.
 
Acknowledgements
The authors would like to thank the research council of the Soil and Water Research Institute, Iran for the financial support of this research.
 
Ethical considerations
The authors avoided data fabrication, falsification, plagiarism, and misconduct.
 
Conflict of interest
The author declares no conflict of interest.