تحلیل پیامدهای فرسایش بادی بر ویژگی‌های شیمیایی و میکروبی خاک بوم‌سازگان خشک در ایرانشهر استان سیستان و بلوچستان

Introduction and Goal
Soil degradation is closely related to the increased wind erosion, which is a major environmental challenge worldwide, especially in arid and semi-arid regions. Because, in these areas, soils have low cohesion and their structure is unstable and vegetation cover is sparse. In addition to the widespread effects of wind erosion on climate, air quality, and human health on a global scale, fine organic particles present on the soil surface are displaced and destroyed by this phenomenon. This process leads to a significantly reduces nutrient reserves, reduces fertility, and destroys the physical and biological structure of the soil. Considering the arid climatic conditions of the Iranshahr region in Sistan and Baluchestan Province and the effective role of strong winds in increasing wind erosion, investigating the consequences of this phenomenon on changes in soil properties is of particular importance. Therefore, this study aimed to investigate the consequences of wind erosion on the physical, chemical, and microbial properties of the soil of arid ecosystems in Iranshahr.
Materials and Methods
In the present study, based on field visits, field observations, and erosion maps of the region, the intensity of soil erosion as the main treatment was categorized into four levels: no erosion, low, moderate, and severe erosion. To investigate the effects of these treatments on soil property variations, sampling was conducted in the Rahmatabad watershed of Iranshahr using a completely randomized design in June 2023. At each erosion level, four homogeneous sites with approximately similar physiographic conditions were selected, and five soil samples were collected from each site at a depth of 0–30 cm. The samples were combined using a composite method. Some of the samples were transported to the laboratory immediately after harvest in sealed containers to measure biological properties, while maintaining the initial humidity, and stored in a refrigerator. The other part was prepared for determination of physical and chemical properties after drying in the open air and passing through a 2 mm sieve. Physical properties including soil texture, bulk density, and porosity; chemical properties included organic carbon, total nitrogen, available phosphorus and potassium, pH, and electrical conductivity; and microbial properties included catalase enzyme activity, basal and induced microbial respiration, microbial biomass carbon and nitrogen, and microbial contribution were evaluated. Data were analyzed using one-way analysis of variance (ANOVA) in SPSS version 26, and mean comparisons were performed using Duncan’s multiple range test at a 95% confidence level. Additionally, correlations among the studied properties were evaluated using R software.
Results and Discussion
The research findings showed that the effect of wind erosion intensity on the physical, chemical, and microbial properties of the soil was significant. Data analysis revealed that as erosion intensity increased, organic carbon and total nitrogen decreased significantly. Soil organic carbon decreased from 0.59% in non-eroded areas to 0.16% and total nitrogen decreased from 0.063 to 0.016% in severely eroded areas. Also, the sensitivity of available potassium and phosphorus to erosion was very high, with potassium decreasing from 161.3 to 79 mg/kg and available phosphorus decreasing from 8.32 mg/kg to 3.45 mg/kg, which was probably due to the movement of fine, nutrient-rich particles by the wind. Soil electrical conductivity of the soil increased with increasing erosion intensity from 0.54 dS/m in areas without erosion to 0.93 dS/m in severely eroded areas. Soil bulk density also increased from 1.36 to 1.58 g/cm³ and the porosity decreased from 46.6% to 33.2%, indicating greater soil compaction and degradation of soil aggregate structure. The decrease in catalase enzyme activity, basal and stimulated microbial respiration, biomass nitrogen, and microbial population was significant (p< 0.01) with increasing erosion intensity. These findings indicated limited food resources and reduced metabolic activity of microorganisms. However, change in biomass carbon to nitrogen ratio and soil microbial contribution were not significant (p < 0.05). This finding indicated the relative stability of some microbial processes even under severe erosion conditions. The results of this study showed that wind erosion reduced both the quality and quantity of soil nutrients and organic matter, and had a severe impact on soil structure and microbial activity. Therefore, these indices can be used as appropriate criteria for evaluating the effects of wind erosion in arid ecosystems, especially in Iranshahr. Correlation analysis showed that the effect of soil erosion on microbial characteristics was very negative. The correlation of catalase enzyme activity (−0.96), microbial respiration (−0.96), microbial carbon biomass (−0.95) and nitrogen (−0.98), and microorganism population (−0.98) with erosion intensity was very high and negative. Biological indicators functioned in a dependent manner, such that the relationship between the biomass carbon to nitrogen ratio and the microbial contribution was highly positive (0.92). These findings confirmed the reduction in the performance of the soil microbial network under the influence of erosion.
Conclusion and Suggestions 
The results of the study in Iranshahr indicated that the best physical, chemical, and microbial soil conditions were observed in the treatment without erosion. The lowest specific gravity, highest porosity, highest water retention capacity, and highest soil microbial activity were related to the aforementioned treatment. As erosion intensity increased from low to high, soil quality steadily decreased; so that under conditions of high erosion, the greatest destruction of soil structure, reduction of available carbon, nitrogen, potassium, and phosphorus, and increase in electrical conductivity were observed. These findings indicated that optimal stability of the structure and function of dryland ecosystems is possible under conditions where minimal or no erosion occurs. Therefore, based on the results of this study, it is recommended to protect vegetation cover, reduce overgrazing, reduce plowing, and increase organic matter to prevent soil from entering advanced stages of erosion.