نشریه مهندسی اکوسیستم بیابان
پیاپی 31 (تابستان 1400)

Vegetation plays a significant role in reducing wind speed and controlling aeolian erosion. Therefore, understanding the interaction between wind and vegetation is of great importance. Vegetation, which grows typically in crops, wind strips, shelterbelts, and windbreaks, helps shelter the ground surface, reduce wind speed, and trap blown sediment particles. It also alters airflow and affects the properties of the turbulent flow. Thus, analyzing the interaction between wind and vegetation is essential for assessing the wind forces exerted upon plants. Although several studies have examined the effect of vegetation on reducing wind velocity and its interaction with airflow, the relationship between the vegetation effect and wind velocity and airflow needs to be investigated. Moreover, while some studies have evaluated the reductionist effect of windbreaks (artificial or live windbreaks) on wind velocity, the airflow's turbulence intensity in windbreaks has not been well researched. Therefore, this study sought to investigate the variations of wind velocity, turbulence intensity, and standard deviation of wind speed to offer valuable information regarding the effect of vegetation on airflow.   

Located in southeastern Iran, the Sistan region is characterized by an arid and hyper-arid climate, low air humidity, low precipitation, high annual temperature and evaporation, and strong winds and dust storms. The most important meteorological-atmospheric phenomenon in this region is the Levar northerly wind (known as 120-day wind) that blows from the end of June to early September, which is considered the main factor in causing dust storms and controlling dust emission and air quality over the region. Placed in high dusty corridors, the windbreak is located in the Niatak area in the northwestern part of Sistan, which is recognized as a critical wind erosion area. Containing fourteen rows of Tamarix trees planted perpendicular to the prevailing wind direction, the windbreak has a mean height of four meters. The distance between the rows varies from 21 to 32m, and the distance between the trees in each row is about 1.5 m. To assess wind speed variations and turbulence intensity, the wind speed was measured upwind, within, and downwind of the windbreak at the heights of 20, 80, 200, 360, 450, 570, and 700 cm in wind speeds of 10.5 and 19.5 m/s. The mean and standard devastation of each wind speed was calculated. Also, the turbulence intensity was obtained by dividing standard devastations by wind speeds.    

Wind speeds were found to be normal in the examined wind velocities (10.5 and 19.5 m/s) in all locations. The pattern of wind velocity variations was similar in all heights outside and inside of the windbreak. Moreover, the wind velocity changed simultaneously in all elevations and fluctuated in a smaller range inside the windbreak, implying lower wind velocity within the windbreak than its upwind and downwind. The wind speed downwind of the windbreak was lower than its upwind at a distance of 50 h (h is the height of the windbreak). These observations indicated that wind speed was affected within and downwind (in a long-distance) of the windbreak.Furthermore, while the wind speed was reduced, the turbulence intensity and standard devastation were increased within the windbreak. The highest turbulence intensity and standard devastation were found at the beginning of the windbreak, where wind velocity was at its lowest rate. A comparison of turbulence intensity in wind speeds of 10.5 and 19.5 m/s in all locations showed that it was similar upwind of the windbreak but different in two wind speeds within the windbreak. However, this different turbulence intensity was reduced at the downwind of the windbreak. It was also found that the turbulence intensity and standard devastation were greater in wind speeds of 10.5 than 19.5 m/s. Moreover, the turbulence intensity in the 19.5m/s wind speed within the windbreak was roughly 20-30% less than what was found in the 10.5 m/s wind speed.

wind speed and turbulence intensity were significantly affected by the windbreak. Investigation of the wind speed, turbulence intensity, and standard devastation upwind, within, and downwind of the windbreak showed low wind velocity. However, turbulence intensity and standard devastation were greater within the windbreak than the upwind and downwind of the windbreak. Furthermore, turbulence intensity was influenced by the windbreak because, in 10.5m/s and 19.5m/s wind speeds, it was similar upwind and outside the windbreak's impacted area but different within the windbreak

The growing trend of desertification is one of Iran's most serious environmental, economic, and social problems, making the identification of the desertification processes and their causes and intensification an important and necessary task. Therefore, to provide a model for showing the intensity of desertification and determining the most critical factors involved in desertification and its prevention, it is necessary to select appropriate criteria and indices.Characterized by a dry climate, low rainfall, unfavorable soil conditions, unprincipled land-use change, and increased wind erosion, Sarakhs city is facing a critical desertification crisis which has led to severe environmental problems as it is considered the center of wind erosion crisis. Thus, considering the critical environmental and human problems existing in Sarakhs and the strategic position of this city, this study sought to assess the severity of the risk via the Iranian model IMDPA and calculate and prepare a desertification risk map of the region. To this end, all the criteria required by the model were evaluated. As the desertification risk maps and the effective indicators of the region's desertification serve as a suitable and efficient tool for managing desertification crises, the prioritization of the crisis management program and the type of programs will be determined.

The Iranian IMDPA method, the geometric mean of nine climatic criteria, and relevant indicators in terms of geology, vegetation, agriculture, water, soil, water and wind erosion, social and economic issues, urban and industrial development were used to assess the severity of desertification. The scoring of criteria and indicators was performed in work units, which are the faces of subsistence. Risk assessment of desertification was performed by combining the risk map of desertification risk, hazardous elements, and the degree of environmental vulnerability using a global risk equation. After identifying the desertification risk classes and the natural and human elements across them via expert opinions and field facts, the vulnerability classes of the elements were determined according to the type of class of the risk severity. To calculate the quantitative value of environmental vulnerability, each element's hazard map and conditions were considered economically and ecologically. Elements at higher risk were also vulnerable. This evaluation was based on the relevant executive departments' expert opinions according to the regional conditions, which can have different values ​​in different regions. Finally, the product of the risk classes of desertification (H) in the classes of hazardous elements (E) and the degree of vulnerability of the elements (V) in the GIS environment of the risk classes (R) was determined.

Lithographic maps, physiography, land use, and satellite images were prepared and integrated with the GIS environment to achieve work units' maps. After combining the maps in the ArcGIS geographic information system environments version 10/2, work units were obtained to be reviewed and corrected. Moreover, land use maps, geology, and surface cover maps were located via Google Earth images to be further adapted to the landforms. Finally, three units, 22 brigades, and 67 geo-biophysical faces were separated in the study area. Based on the criteria's geometric mean and the characteristics of desertification in the IMDPA model, the numerical value of each of the faces was estimated to be 3, indicating the severe intensity of desertification in the region. In terms of zoning, the region was classified into low classes with an abundance rate of 0.6, medium classes with an abundance rate of 18.8, severe classes with an abundance rate of 6.9, and very intense classes with an abundance rate of 11.7.Among the factors involved in desertification, wind erosion criteria, vegetation, agricultural and socio-economic factors had the most significant impact on the intensity of desertification in the region with an average weight of 3.5. Moreover, the vulnerability and sensitivity of the phenomena showed that low-sensitivity elements covered more than 35% of the area, and sensitive middle-class elements covered more than 64% of the area. Also, the number of risks was calculated and classified into four categories ranging from low to high via global risk equation, with their frequency reported to be 11.97%, 26.53%, 46.24%, and 15.26%, respectively. In this regard, it was found that more than 60 percent of western and eastern Sarakhs were on a high and very high-risk level in terms of desertification. These areas were home to many agricultural lands.

According to the study's results, it was found that more than 80% of the whole study area was classified as severe and very severe in terms of desertification. Furthermore, wind erosion, vegetation, agriculture, and socio-economic criteria had the most significant impact on the region's desertification process, with their weight value reported to be 3.5 on average. In general, using the Iranian IMDPA model, which is compatible with Iran's climatic and environmental conditions, especially with the study area, helped assess the region's desertification intensity. Also, considering the use of intensity maps and the existence of hazardous elements and environmental vulnerabilities, the application of the global risk model indicated the possibility of the development of desertification in the region. It could be argued that evaluation of hazardous elements, especially the human and economic ones, is a good practice to assess environmental vulnerabilities, a fact that this study attempted to apply appropriately. It should also be noted that a desertification intensity map alone cannot be a helpful tool for providing a desert crisis management program. While the region could be at a high risk of desertification,  the desertification risk would not be significant due to the lack of endangered elements, and thus, it would not be a priority in the Desert Crisis Management Program. Therefore, in addition to the desertification intensity map, the endangered and vulnerable elements' map is also of great importance. The novelty of this applied research lies in its assessment of the desertification intensity and risk.

In recent decades, flood-spreading and artificial flood recharge have been used at the proper time and place for optimal utilization of floods in arid and semi-arid regions. The importance of these projects in Iran is mainly due to the excessive use of groundwater resources and recent droughts, which have rapidly decreased the level of underground aquifers. Therefore, in a country like Iran, which is regarded as an arid and semi-arid region, performing such projects is essential for water resources management and flood control. Evaluation of the performance of watershed management projects in different countries worldwide has a history of more than 80 years. Thus, this study sought to determine the long-term effects of this project on flood control and underground water recharges, especially in dry years, through a technical investigation of the Mehriz flood-spreading project.

This study used technical evaluation methods to evaluate the Mehriz flood-spreading project, which was carried out in two ways: statistical analysis and fieldwork. In the first method, all necessary data were collected and analyzed. In the second method, field visits to the project were made, the pros and cons of the note plan were identified, and the technical evaluation of the plan was performed. This way, the discharge of qanats was investigated before and after applying the water-spreading project.

The comparison of average annual discharge in Fakhrabad River's hydrograph before and after the project shows that from July to November, the flow rate in each period was equal to zero, and from December to April, the river's flow rate was less in the pre-project period than what it was in the post-project period. Moreover, the average discharge rate in the month before the project began was lower than the rate reported after the project finished. Also, the average rate of post-project discharge in May and June was less than the rate reported for the pre-project period. The study's results indicate that while most pre-project floods occurred in late spring and early summer, the post-project floods occurred in late winter and early spring.

As mentioned earlier, this study investigated the effect of the Mehriz flood-spreading project on qanat discharge. According to the study's results, Baghdadabad's qanat in pre-project years was less than that of control 1 (Ibrahim Abad) and control 2 (Henza). During the years since the project was implemented, these qanats' discharge rate was higher than that of both control qanats. A comparison of the three-year mean discharge of the Baghdad qanats in May, August, and February in two ten-year periods before and after the implementation of the project showed that these qanats' discharge rate was increased in pre-project years. Therefore, implementing the flood-spreading project has helped increase the volume of water in those qanats. Also, the result of the statistical t-test showed that this aqueduct's flow rate has increased in pre-project years.The changing trend of the Khairabad qanat's discharge in Yazd indicated the positive effect of implementing the flood-spreading project on the qanat's discharge in post-project years. On the other hand, the result of the t-test for Mohammadabad qanat before and after the implementation of the project suggested that the qanat's discharge rate in pre-project years was less than the rate reported for the post-project years. Also, a hydrological comparison of the average quarterly discharge rates of the qanats with those of the control qanats pre and post-project years showed that the discharge rates of Khairabad and Mohammadabad qanats had gone through a downward trend from 1987 to 2007, indicating no effect of the flood-spreading project on increasing the discharge rate, which is considered as one of the drawbacks of the flood distribution plan. This could be attributed to the fact that the project area is located in a place where flood water naturally spreads and nourishes most channels. Moreover, diverting the water of the Fakhrabad channel and spreading the flood water to a particular place prevents some downstream qanats (such as Mohammadabad) from being fed by the floodwater, which, in turn, may upset the floods' balance and negatively affect the behavior of the basin's residents.

Particle size distribution (PSD) is one of the sediments' most important physical properties, affecting other physicochemical properties. Fractals are the objects or processes that show a similar appearance or behavior on some large, spatial, or temporal scale. Each fractal can be divided into several parts, each of which resembles the main body. Many natural phenomena and processes are based on fractal models. Loess particles maintain good self-similar properties even when modified through pedogenesis so that the fractal dimension of their particle size is considered as a new indicator of particle size. The loess sequences, produced by aeolian under the influence of past weather changes, have been transported, deposited, and undergone many changes by pedogenesis, whose information is recorded in loess particles. By studying the PSD loess, which is a natural fractal, one can discover data about the past environment. Therefore, PSD changes can be used to indicate the pedogenesis intensity and process or the soil age.Post-depositional pedogenesis, including chemical and biological weathering, causes further particle crushing, the extent of which may vary in different locations due to deposition PSD and the time and intensity of pedogenesis or some other factors. Typically, intense pedogenesis or poor to very poor sorting occurs in warm and humid climates, while poor pedogenesis occurs in cold and dry climates. Changes in the loess texture reflect its post-deposition conditions. Thus, this study sought to analyze Golestan's loess texture developments via fractal PSD for the first time, which could interpret the extent of tissue changes at different points. The results were then compared to the fractal geometry obtained from the electron microscope images.

This study was conducted in Golestan province. The study area is located at latitudes of 38° 8' to 36° 30'N and longitudes of 53° 57' to 56° 22' E. Based on three types of loess texture, including sand loess, silt loess, and clay loess, sixteen samples were totally collected from three zones. Moreover, the fractals were measured using differential box-counting and PSD. The PSD fractal was calculated by sieve-hydrometric (DbH) and laser (Dbl) methods.

The mean DbH for region 1 was 2.64  and region 2 was 2.30. DbH in region three differed in two values. For two regions S12  and S13, the values of DbH are 2.74  and 2.70 and for S 14, S15 and S16 are 2.62,1.06 and 2.24 respectively. Also, the results showed a mean of 4.37 microns and sorting is very poorly (mean φ = 2.96) for region one, a mean of 14.35  microns and sorting is very poorly (mean φ = 3.17) for region two and  a mean of 49.56 microns with two different sorting values show very poorly sorting (mean φ = 2.28) at S13 and S12 stations and sorting poorly (mean φ = 1.78) at stations S16, S15, S14  for zone three. The average fractal grain dimension in region one is 0.673  in region two is 00.788  and in region three is 0.850.. The fractal dimensions of the grain surface in region one have an average of 0.51  in region two is 0.49  and in region three is 0.50. The average value of fractal geometry of grain density arrangement (DFf) is 1.94  in region one, 1.87 in region two and 1.91 in region three.The average fractal arrangement of pore fabric density (DFp) in region one is 1.47  in region two and 1.5  in region three is 1.59.. The fractal geometry of the cement fabric density arrangement is 1.33  in region one, 1.43 in region two and 1.52 in region three.

The results of examining DbH dimensions in the loess of Golestan province show that the percentage of sand decreases and the clay content increases with the increase of DbH. Comparison of fractal with sediment textual parameters indicate that the number of sorting increases and the sorting of particle decreases with the increase of DbH. This means that the samples have a better gradation of PSD and a larger volume of particle size classes. The kurtosis index decreases with the increase of DbH and the curvature broadening increases as a result of the increase of the particle size classes.The results of examining DbL fractal dimensions in the loess of Golestan province show that the percentage of sand decreases and the silt and clay contents increase with the increase of DbL. Based on the results of laser sizing, the increased silt and clay contents lead to a better gradation of sediments. The negative trend of particle sorting against DbL means that the sorting index decreases and the particle sorting increases with the increase of DbL. The positive trend of kurtosis against DbL means that the kurtosis index increases and the curvature broadening decreases with increase of DbL.Three stations of AlmaGol, AlaGol and Agh Ghala Belt in zone 3 had lower DbH and DbL, better sorting, and the highest median size. This may be due to the differences in the sediments’ origins or forming environment and retransfer. This implies that the fractal values ​​can be useful for identifying the transfer mechanism in different sediments.The fractal geometry changes with the changes in loess texture. Therefore, a higher fractal dimension content indicates a higher soil formation and higher fine particle ratios. According to the results, if particle distribution is well graded, it can be claimed that fractal geometry demonstrates the changes after loess deposition. According to the fractal results obtained from electron microscope images in Golestan loess, the fractal dimensions of the grain increased with the increase of diameter. This confirms that near the source, grains are deposited with higher order and away from the source, the fractal number becomes smaller as the grain size decreases. The fractal dimensions of the grain decrease with the increase of particles roundness from zone 3 (near the source) to zone 1 (away from the source). This implies that the sedimentss order decreases and the texture undergoes less changes with the increase of particles roundness. On the other hand, the fractal grain dimensions increase with the increase of sphericity. Since the sphericity decreases from zone 3 to zone 1, the fractal number of grain dimensions decreases. This means that a higher sphericity leads to a higher initial order of the sediment and less texture exposure to changes.The fractal geometry values ​​of the grain fabric density of the fabric in different parts of Golestan province are not equal. Zones 3 and 1 have a higher order than zone 2. Zone 3, with the fractal number close to 2, has a high order during the deposition due to its proximity to the source. In zone 2, with a farther transfer, the particles have been highly subjected to changes in size and arrangement, and thereby the fractal number and order have been subjected to changes and decline. The highest fractal number is seen in zone 1. This can be due to the humid climate in zone 1, which induces the formation of secondary clay and increases the fractal numbers and sediment order. These results show that the content of clay can determine the order and homogeneity of the sediment texture. It can be concluded that fractal and its related parameters, as an efficient tool in analysis of loess sediment, can justify the zone of texture changes, distance from the main source, pedogenesis and climate and The results of DbH dimensions analysis in Golestan province's loess showed that the percentage of sand decreased, and the clay content increased with an increase in DbH. Comparing the fractal with textual sediment parameters indicated that the number of sorting increased and the particle sorting decreased with an increase in DbH, suggesting that the collected samples had a better PSD grading and a larger volume of particle size classes. Moreover, it was found that the kurtosis index decreased with an increase in DbH, and the curvature broadening increased with an increase in particle size classes.The results of Dbl fractal dimensions analysis in Golestan loess showed that the percentage of sand decreased, and the silt and clay contents increased with an increase in DbL. Furthermore, according to the results of laser sizing, the increased silt and clay contents led to a better sediments gradation. A negative trend of particle sorting against DbL means that the sorting index decreased and the particle sorting increased with an increase in DbL. on the other hand, a positive trend of kurtosis against DbL means that the kurtosis index increased and the curvature broadening decreased with an increase in DbL.Three stations, including AlmaGol, AlaGol, and Agh Ghala Belt in zone 3, had lower DbH and DbL, better sorting, and the largest median size, which could be due to the differences in the sediments' origins or the environment's form and retransfer, implying that the fractal values could help identify the transfer mechanism in different sediments.The fractal geometry would change with the changes made in loess texture. Therefore, a higher fractal dimension content indicates a higher soil formation and higher fine particle ratios. According to the study's results, should the particle distribution is well graded, it can be claimed that fractal geometry demonstrates the post-deposition changes in the loess. Based on the fractal results obtained from electron microscope images in Golestan loess, the grain's fractal dimensions increased with an increase in diameter, indicating that the grains are deposited with higher-order near the source, and the fractal number becomes smaller with the decrease in the grains' size away from the source. It was also found that from zone 3 (near the source) to zone 1 (away from the source), the grains' fractal dimensions decreased with an increase in particles roundness, implying that the sediments' order decreased and the texture underwent fewer changes with an increase in particles roundness. On the other hand, the grains' fractal dimensions increased with an increase in sphericity. Therefore, as the sphericity decreased from zone 3 to zone 1, the fractal number of grain dimensions decreased too, indicating that higher sphericity led to a higher initial order of the sediment and less texture exposure to changes.The fractal geometry values of the grain's fabric density in different parts of Golestan province are not equal. Therefore, zones 3 and 1 had a higher order than zone 2. Due to its proximity to the source, zone 3, with the fractal number close to 2, had a high order during the deposition. In zone 2, with a farther transfer, the particles were highly subjected to changes in size and arrangement, and thereby the fractal number and order were subjected to changes and decline. Moreover, zone 1 was found to have the highest fractal number because of its humid climate, inducing secondary clay formation and increasing the fractal numbers and sediment order.These results suggest that the content of clay can determine the order and homogeneity of the sediment's texture. Therefore, it can be concluded that as an efficient tool in analyzing loess sediment, fractal and its related parameters can justify the zone of texture changes, distance from the main source, pedogenesis, and climate, and determine the model of post-deposition changes.

Changes in land cover and land use effect on natural processes such as soil erosion and sediment production, flooding and soil physical and chemical properties. One of the important impacts of land cover type on processes in watersheds is its role on soil erosion rate. The purpose of this study was to investigate the effect of vegetation changes and conservation factor on soil erosion in Doiraje watershed of Ilam province using GIS and RUSLE model . The results showed that the changes in Landuse/cover  increased the amount of soil loss. Soil conservation scenarios showed that with all factors constant, soil conservation with a correlation coefficient of 0.46% was secondarily important after topography with a correlation coefficient of 0.81% in determining soil erosion. The highest soil erosion under the soil conservation scenario was 2015, with an average of 48.91 ton / ha. Examination of land use / cover change scenarios showed that by keeping all factors constant, soil protection with a correlation coefficient of 0.46% in the second place after topography with a correlation coefficient of 0.81% and vegetation factor in the third degree played an important role in determining the amount of soil erosion. Is. The highest soil loss under the third scenario was in 2015 with an average of 108.94 tons per hectare per year.

The soil's biological crusts increase soil's organic matter, especially in arid and semi-arid regions, performing a special function in the global carbon cycle. Organic soil carbon, which is a mixture of various components, including organic acids, is an important indicator of soil quality. Organic acids increase the solubility of low-soluble nutrients, including soil iron. Therefore, this study attempted to investigate the effect of biological shells in increasing soil organic acids and their participation in iron uptake.

The map of biological soil crusts' distribution in the Sejzi plain was prepared, and soil was sampled under cover of biological soil crusts from lichen-dominated areas. Then, soil's physicochemical properties, including pH, EC, Fe, OC%, CaCO3%, and soil texture, were measured. Next, the Pearson correlation coefficient was calculated to determine the relationship between soil parameters and biological soil crusts. The values of the soil's physicochemical parameters were classified into two classes (soils covered by biocrust and non-biocrust) via PCA (Principal Component Analysis) using Matlab 2013b software. Then, loading charts for the first, second, and third components were calculated at the confidence level of 67.51%, 21.73%, and 6.71%, respectively. Fourier-Transform Infrared spectroscopy was performed, and FTIR spectra were obtained for all collected soil samples to identify the existence of an organic acid agent in the soil.

In the study area, 32 specimens of terrestrial lichens were collected from the Sejzi desert, most of which had been classified as cyanolichens whose photobiont part was cyanobacteria.The Pearson correlation coefficient between the percentage of organic matter and the coating of biological soil crusts was reported to be 0.653, indicating the significance of biological soil crusts in increasing soil organic carbon. Also, the results of the t-Student test showed that the amounts of absorbable iron in biocrust-covered and biocrust-free soils were significantly different.The classification of the relevant parameters via the PCA method revealed that in the Sejzi plain, soil salinity with 67.51% confidence, and at 21.73% level, soil texture and lime percentage were among the most important limiting factors in the establishment of biological soil crusts.Based on FTIR curves, Citric acid and oxalic acid were read from 1400 to 1600 (cm-1) and 1700 to 1800 (cm-1), respectively.

Deserts, arid, and semi-arid ecosystems contain very small amounts of organic matter, and, thus, they are exposed to the destructive effects of physical and chemical agents. Therefore, biocrusts, which play a very influential role in increasing the soil's organic compounds, improve the properties of desertified soils and enhance the desert's health. Moreover, secreting organic acids that form part of the whole soil's organic matter, biological soil crusts act like plant roots and facilitate chemical reactions in arid and semi-arid soils that are considered poor in terms of fertility. According to the study's findings, calcium carbonate, which increases soil alkalinity and affects the establishment of biological soil crusts, was found to be a limiting factor in carbon sequestration in the Sejzi plain. In other words, with an increase in calcium carbonate, the carbon sequestration and the amount of soil's organic carbon decreased.On the other hand, increased pH in the soil reduces the efficiency of organic acids such as citrate and oxalate, and as a result, the plants' absorption of the soil's micronutrients, including the iron, was reduced, and the growth of aerial parts and roots of the plant was disrupted.Furthermore, it was found that the probability of the formation of the lichen-dominated biological crust is 21.73% in sandy and silty soils, which contain more sand and silt than the clay soils. Also, in the Sejzi plain, fewer biocrusts are established incalcareoussoils. Moreover, in deserts, biocrusts increase organic carbon and thus perform different functions compared to other regions. However, they do not increase aggregate soil stability by increasing calcium carbonate. It should be noted that most of the Sejzi desert's biocrusts produce organic matter and increase soil's organic carbon, and a few of them are of calcium carbonate-producing types. Finally, it could be argued that biological soil crusts significantly increased iron absorption, which is considered as one of the most important micronutrients in the soil, by increasing the organic matter, which is among the categories found in the soil's organic matter. An increase in iron absorption was especially significant in the Sejzi plain's soils with high alkalinity (pH 7.5), limiting micronutrients dissolution and subsequently disrupting the establishment of vegetation.

Salinity is an important environmental stressor that affects plant growth. In saline soils, plants are subjected to some toxic ions and water shortages. Crop residues are considered major organic agricultural wastes that can be useful for the soil and the plants. Organic matter has positive effects on the soil's physical and chemical properties. Converting agricultural wastes to Biochar is an appropriate way to achieve a valuable amendment. Biochar is a carbon-rich decomposition-resistant product obtained by heating biomass in an oxygen-free chamber, being used for carbon sequestration by applying large amounts of carbon.Moreover, as a highly stable residue in the soil, it has been proven to store atmospheric carbon for hundreds to millions of years. According to different studies' findings, the application of Biochar can increase the soil's water-holding capacity, microbial activity, and nutrient availability. However, its effect on soil properties depends on its source and the extent of its application.  As the dependency of Biochar's effects on saline soils' properties in such soils has been under-researched, this study attempted to investigate the effect of palm-tree residues' Biochar on the physical and chemical properties of saline soils.

the required Biochar was prepared from palm trees' residues at 500°C under limited oxygen conditions. This experiment was conducted in a completely randomized design with three replications. Biochar was mixed at 0, 0.5, 1, 1.5, and 2% rates with saline soils and incubated with humidity at field capacity for 90 days. Then, the samples were air-dried, and some physicochemical characteristics of the soil were determined. Moreover, the comparison of the means was performed using Duncan's test at a confidence level of 95%.

The results showed that applying the Biochar obtained from palm trees to the soil significantly increased the soil's chemical properties such as electrical conductivity (EC), organic carbon, calcium, magnesium, sodium, and potassium while decreased the sodium adsorption ratio (SAR), and the sodium/potassium ratio. Moreover, while adding Biochar to the soil increased the porosity by 10% and reduced the bulk density by 4%, treatments did not significantly affect pH, available phosphorus, field capacity, and the soil's particle density. Furthermore, adding 2%, Biochar increased calcium concentration in soil by 2.08 times compared to that of the control treatment. It was also found that the changes in the soil's magnesium calcium were similar and that using more Biochar increased magnesium concentration by 2.88 times compared to what was observed in the control treatment (more than the control treatment). Therefore, the study's findings indicated that the available potassium concentration in soil increased significantly following the application of different biochar levels. It was also found that compared to the control treatment, the amount of potassium increased about 12.33 and 18.79 times, respectively, with an increase of bio-dates in 1.5 and 2% treatments. Moreover, the highest increase in sodium was related to applying a 2% biochar date, which was 49.35% more than that of the control treatment. Finally, using 2% biochar reduced the sodium adsorption ratio by 7.6%.

This study showed that palm trees' Biochar improved some saline soil parameters such as SAR, organic matter, and nutrients. Increased EC is due to increased sodium as a destructive factor and other cations such as calcium, magnesium, and potassium as helpful plant nutrients. On the other hand, the sodium to potassium ratio was decreased. Moreover, it was suggested that the potassium was increased more than sodium, and that was why the index was improved. According to the study's findings, Biochar increased porosity due to its high specific surface area.Moreover, using 2% biochar treatment increased the saline soil's organic carbon by approximately three times. Due to the Biochar's low specific gravity, it can be expected that the soil's density is decreased by applying Biochar in soil. However, the increase in Biochar did not significantly affect the soil's particle density, which is probably due to the low weight of biochar particles versus the high weight of the soil's minerals and the amount of Biochar applied. It seems that applying Biochar as an amendment can improve the saline soil's properties and that the size of biochar particles may have different effects on changing the soil's properties, which can be investigated in future researches.

while global Climate Models (GCMs) are designed to assess climate change, they can only simulate large-scale atmospheric circulation model data. Therefore, these models' results need to be downscaled, for which there are different methods such as dynamical and statistical ones.This study sought to investigate the effect of climate change on temperature, precipitation parameters, and drought in 2050-2031 and 2070-2051 periods in Khatam city using two general circulations models, namely BNU-ESM and HadGEM2. Moreover, as using only one downscaling model to achieve a perspective concerning the future climate of the study area with the slightest uncertainty does not seem logical, LARS-WG and Change Factor (Delta) were used as two downscaling models under RCP2.6, RCP4.5, and RCP8.5 scenarios.

The Khatam city is located south of the Yazd province, Iran. In this study, the data obtained from the synoptic station of Marvast were applied. The historical data from 1996 to 2017 comprised the daily temperature and precipitation. Moreover, the data collected from two large-scale models including HadGEM2-ES and BNU-ESM and two statistical downscaling methods, i.e., LARS-WG and Change Factor (CF), were applied to simulate precipitation, temperature, and drought in Khatam city under three scenarios including RCP2.6, RCP4.5, and RCP8.5 in 2031-2050 and 2051-2070 periods. Also, statistical indices such as R2, RMSE, and NSE were used to evaluate the accuracy of the CF method and the LARS-WG model. To assess the drought in the baseline period (1996-2017) and the two future periods, the standardized precipitation index (SPI) was used based on a 24-month scale.

The results of temperature variations regarding 2031 to 2050 and 2051 to 2070 periods indicated that based on the LARS-WG model, the Khatam city would be affected by global warming, with temperature changes suggesting a 1.75, 1.94, and 2.12 °C increase from 2031 to 2050, and 2.07, 2.71, and 3.87 °C from 2051 to 2070 under the scenarios of RCP2.6, RCP4.5, and RCP8, respectively.The results concerning annual precipitation variations based on the LARS-WG model showed that precipitation would be decreased by 6.1, 14.2, and 35.2% from 2030 to 2051, and by 26.8%, 35.5., and 51.5% from 2051 to 2070 under RCP2.6, RCP4.5, and RCP8.5scenarios, respectively. Also, investigating annual temperature and precipitation changes based on the BNU-ESM model suggested an increase in temperature by 1.06, 1.83, and 2.13 °C from 2031 to 2050, and by 1.084, 1.94, and 2.82 °C from 2051 to 2070 under the RCP2.6, RCP4.5, and RCP8 scenarios, respectively.The results of annual precipitation variations based on the BNU-ESM model showed that precipitation would decrease by 14, 22.1, and 32.9% from 2030 to 2051 and 24.2%, 33.9, and 48.1% during 2051 to 2070 under RCP2.6, RCP4.5, and RCP8.5 scenarios, respectively. It should be noted that after determining the climatic parameters for future periods, the SPI values for future periods and three scenarios can be determined.Moreover, the results indicated an increase in meteorological drought based on the HadGEM2 and BNU-ESM models for the two future periods under all scenarios compared to the baseline period. Also, the BNU-ESM showed higher drought compared to the HadGEM2 model.

as mentioned earlier, both downscaling models used in this study had a high accuracy in predicting future precipitation and temperature, which is consistent with the results found by Sadidi et al. (2020) in Kerman province, and the findings reported by Panahi and Khorramabadi (2020) in East Azerbaijan province. The study's findings concerning the two future periods' temperature changes in both models indicated that the Khatam city would be affected by global warming, indicating an increase in temperature from 2031 to 2050 and from 2051 to 2070 under RCP2.6, RCP4.5, and RCP8.5 scenarios, respectively.  Also, results regarding the precipitation changes in both models suggested a decrease in precipitation from 2031 to 2050 and from 2051 to 2070 under RCP2.6, RCP4.5, and RCP8.5 scenarios, respectively, with the greatest decrease, occurred under the RCP 8.5 scenario, that is in accordance with the results found of Givati et al. (2019) in the upstream of the Jordan River. Moreover, the current study's results indicated the possibility of more severe droughts in future simulated periods by the LARS-WG downscaling model and CF method, which is compatible with the findings reported by Lucas and Et al. (2008), Lebedzki (2006), and Saleh Pourjam et al. (2014).  It could be argued that the increase in the severity of drought in future periods is due to the increase in temperature and decrease in precipitation, which is also confirmed by the results found by Node Farahani et al. (2015). According to this study's results concerning the comparison of the two GCM models, it could be said that the BNU-ESM model can predict the lowest precipitation, the highest temperature, and the highest number of years regarding the severe drought compared to the HadGEM2 model.

located in the dry belt of the earth, Iran has more than 164 million hectares of drylands. As the rate of wind erosion has significantly increased in recent years, applying sand dunes' stabilization methods seems essential. Therefore, this study sought to identify the soil bacteria affecting the microbial-induced carbonate precipitation and evaluate different amounts of potash wastewater (SSR400 solution) as a cheap solution for stabilizing sand dunes.

To investigate the possibility of sand dunes' stabilization via industrial wastewater and soil microorganisms, two experiments were designed and performed in 2019 at Yazd University. The first experiment was performed to screen the soil bacteria in those Iran's desert areas with the highest ability to hydrolyze urea. The tested bacteria included four bacterial isolates from the Eshtehard desert, six bacterial isolates from Iran's central desert, and Sporosarcina pasteurii bacteria. The second test was performed to evaluate the stabilization of sand dunes as a two-factor factorial in a completely randomized design with three replications. The first factor included the use of mulch at 0.5, 1, 2 and, 1/3 soil saturation (SP) levels. The second factor was the mulch type that was examined in eight levels: no bacteria, Pseudomonas fluorescens, Sporosarcina pasteurii, Phormidium tenue, Oscillatoria tenuis, b4, distilled water, and potash wastewater (SSR400 solution). Data analysis and statistical calculations were performed using SASV9 and EXCEL software. Also, the mean comparison was performed by the protected LSD test at a 5% probability level.

The results of the urea hydrolysis ability test showed that the bacteria in urea hydrolysis had a significant difference in the level of one percent probability. Comparison of the mean results suggested that Sporosarcina pasteurii with an average of 3223.3 μs/min of electrical conductivity (EC) had the highest ability to hydrolyze urea. In the next rank, the bacteria isolated from the Eshtehard desert's soil (b2) with 2421.3 μs/min of electrical conductivity and the bacteria (b4) with 2072.3 micro Siemens per minute belonged to Iranian central deserts' soil. Moreover, the results of comparing b2 bacterium's 16S rRNA sequence with other bacteria in the NCBI gene bank's database indicated that the ribosomal RNA sequence of the 16S b2 isolate was 99% similar to the sequences of Pseudomonas fluorescens. On the other hand, the analysis of the variance of the second experiment's data showed that the type and amount of mulch application and the interaction of the two had a significant effect at the level of 1% probability on compressive strength and tuber diameter, making the particle's percentage greater than 0.84 mm. Following the application of Sporosarcina pasteurii at the rate of 1/3 soil saturation, the highest compressive strength and the highest percentage of particles larger than 0.84mm were observed to be 4.4 kg/cm2 and 97.5%, respectively. Moreover, the compressive strength of potash wastewater (SSR400 solution) and Pseudomonas fluorescens after applying 1/3 soil saturation was 3.88 and 3.85 kg/cm2, respectively. The highest tuber's diameter at a rate of 5.5 cm was obtained with the application of potash wastewater (SSR400 solution) at a rate of 1/3 of soil saturation. Also, the tube's diameter after applying potash wastewater (SSR400 solution) at the rate of 2 and 1 Lit/m2 was found to be 4.99 and 4.11 cm, respectively. Also, applying Pseudomonas fluorescens and potash wastewater (SSR400 solution) in 1/3 soil saturation led to the creation of 96.4% and 94.4% of particles larger than 0.84 mm, respectively.

The study's results showed that those bacteria with a high ability to hydrolyze urea and deposit calcium carbonate could play an influential role in increasing soil firmness. It was also found that the properties of the calcium, magnesium chloride and calcium nitrate in the potash wastewater (SSR400 solution) increased the adhesion of soil' particles and the soil's stabilization. These solutions increased the surface tension of the soil and strengthened the bond between the soil's particles. Moreover, the calcium ion in potash wastewater (SSR400 solution) effectively softened soil's colloids and reduced erosion.Generally, the qualitative urea hydrolysis test results indicated that while Sporosarcina pasteurii had a high ability in the hydrolysis of urea and the sand dunes' biological stabilization-related traits, Pseudomonas fluorescens was less able in these regards. Moreover, as a mineral mulch, wastewater (SSR400 solution) showed an excellent ability to stabilize sand dunes. However, it should be noted that the very high salinity of this solution can cause many problems in desert lands. Therefore, it is necessary to reduce the solution's salinity before recommending it as mulch. Also, as the application of 1/3 soil saturation increased stabilization in all mulch types, it could be argued that increasing the volume of mulch application per square meter can improve the stabilization of sand dunes. However, due to the limitations of using mulch in desert lands, including water shortages and the difficulty of transporting such solutions to desert areas, applying less amount of the selected mulch may improve soil erosion.

Modeling the allocation of water resources systems in the world has been considered from different perspectives. One of the most important differences in modeling is between linear and dynamic approaches. The term linear refers to a common approach in modeling with a mechanical conception of events that justifies phenomena with unilateral cause and effect relationships. On the other hand, in the dynamic approach, which is also applied in the present study, the system is first broken down into smaller components, the mutual causal relationships between the components are defined, and finally, the combination of their results determines the system's performance. Together with each other, Causal relationships create a Generic Archetype that helps identify the problems and solve them, which could especially be helpful in water resources management. This study sought to simulate surface water allocation in the agricultural sector of Qorveh Dehgolan's basin, dealing with future problems by identifying generic archetypes.

in the study area, drinking water, the water used in industry, and some part of the water used in agriculture are supplied from groundwaters. Thus, the researchers attempted to measure the amount of surface water consumed by the agricultural sector. To this end, first, the model was simulated on an annual scale. Then, after ensuring the model's accuracy, it was implemented on a monthly scale using the Vensim software. Moreover, behavior and condition tests were performed to validate the simulated model, proving the model's high accuracy.

To ensure that the decrease in rainfall does not affect discharge, a comparison of rainfall trends and river discharge was performed in two selected stations, and the results showed that the decrease in river discharge was due to consumption. After that, has been evaluated model in annual scale, we used average values of RMSE and MAE in all stations, results show values equal 0.4 and 0.10 respectively, on the other hand, the test of limit conditions was confirmed high accuracy of the model. In the next stage, the average percentage of computational withdrawals was calculated for the annual scale, and the results showed that the maximum and minimum percentages of water consumption are equal to 27.79 and 19.53 for Dehgolan and Golbalagh stations, respectively. These values ​​indicate a deficit equal to 50% of the water requirement throughout the simulation period. Then, simulations were performed on a monthly scale before and after dam activity. Before operating the dams in the region (until 1390), the RMSE and MAE values were calculated as 0.74 and 0.39, respectively, which confirmed the model's efficiency. Then the impact of dams on the region's behavior and the causes of their occurrence was considered. Despite an intense decrease in discharge, the activity of generic archetypes, such as growth limit, failed fixes, and escalation, have expanded the under-cultivation area in all zones from 1390 to 1395, with the HassanKhan under-cultivation zone being expanded by 4.5 times compared to the previous conditions.

Simulating the dams' post-operation performance model shows that the dams' output can be increased up to 2 times in the best case. An increase in growth-limit patterns failed solutions, and escalation has led to the construction of dams in this region to deal with water shortages crisis and to supply more water, and, thus, to the expansion of under-cultivation areas in all zones with the assumption of the existence of adequate water supplies. Therefore, in addition to the critical decrease in Qorveh and Dehgolan aquifers' water level throughout the 1369-1390 period, the region's discharge rate has dropped by 72% compared to its rate at the beginning of the period (from 1390 to 1395), and by 114% compared to the whole study period due to recent extractions, while according to most of the meteorological station, the precipitation rate has not been decreased so critically.On the other hand, the under-cultivation areas in zones where dams are constructed such as Soral, Sang Siah, and Golbalagh, or under-cultivation areas in areas located downstream of those zones, including Hassan Khan, have been expanded by 2.40, 3.56, 3.93, and 4.5 times compared to the study period's average rate in response to the escalation. As the growth limit and failed solutions have not been applied to these zones yet, this part of the basin has increased the irrigation efficiency from 37% to 45% to maintain the equilibrium. Therefore, considering the observed behaviors, it could be argued that if appropriate measures are not taken to manage water consumption properly, the dams' minimum output and their reservoirs' dryness would be highly expected.