مجله مدیریت بیابان
پیاپی 26 (تابستان 1402)

The impact of dust storms on the ecosystem, human health, and economy is significant in the affected areas. In arid and semi-arid regions, dust is a natural occurrence that covers about one third of the earth's surface. This phenomenon is caused by wind erosion and factors such as the size of soil particles and their adhesion force, surface roughness, weather conditions such as long-term droughts cause it to intensify. To understand the impact of the dust phenomenon on humans and the environment, it is essential to evaluate the spatial and temporal distribution of dust and its changes and effects. Numerous studies have been carried out in the field of evaluating dust changes using different methods. For example, using CMIP5 models, synoptic fog systems are predicted to increase during the 21st century in the Middle East. In addition, using AOD obtained from MODIS and MERRA-2 sensors, researchers showed a significant upward trend in dust changes from 2000 to 2010. A significant upward trend was shown in Iran's winter AOD values during the period 2000 to 2010, and a decreasing trend during the period 2010 to 2018. A point can be spotted by examining various studies in the Middle East and Iran that evaluate the spatio-temporal changes of dust. Statistical tests of time series study, such as Mann-Kendall spatially and pixel by pixel, have been used in limited research to evaluate the trend of dust changes. In Iran, there is a research gap in not using spatial and pixel-by-pixel statistical tests to evaluate the trend of dust changes, as stated. This research aimed to provide a solution and address the problem by analyzing the spatial and temporal changes of dust using the AOD index in the eastern half of the country.

 In this research, in order to evaluate the temporal-spatial changes of dust, the AOD data of the blue band (470 nm) of the MCD19A2 product of the MODIS sensor was used. AOD parameter is known as one of the most key factors in studying the climatic effects of aerosols and atmospheric pollution. In order to extract AOD data, monthly data from 2001 to 2022 were obtained in the Google Earth Engine system by averaging the daily AOD data. Over a 22-year period, the average of each month was calculated. The months that had the highest average AOD values were chosen and their changes were evaluated. In this research, the Mann-Kendall test was used to evaluate the change process. Menkendall's ZM coefficient was calculated for months in the Earth Trend Modeler (ETM) of the TerrSet software to achieve this. In the next step, the intensity of monthly AOD changes per time unit was calculated for 22 years in selected months. To simulate the process of changes, linear regression analysis can be utilized for this purpose. This method is used to determine the linear relationship between all the data of a dependent variable and the corresponding data of the independent index. If the slope is higher than zero, the dependent variable will change in the same direction as the independent variable. The dependent variable changes in the opposite direction of the independent variable if the slope is smaller than zero. The steeper the slope of changes, the greater the impact of the independent variable on the dependent variable. The Earth Trend Modeler (ETM) of TerrSet software also carried out this step.

Based on the evaluation of the monthly average AOD changes in the studied area, the trend and intensity of AOD changes from 2001 to 2022 were assessed in April, May, June, and July. In most areas of the studied area, AOD is increasing with a probability of more than 70%, and the intensity of changes is mostly high and very high in April. It can be concluded that AOD is experiencing a strong increase in April. This is despite the fact that in May, June and July, respectively, a considerable part of the western half, northern half and eastern half is increasing with different intensities with a probability of more than 70%. It can be concluded that the trend and intensity of AOD changes in the above-mentioned months follow a different spatial pattern. The dispersion of dust production centers inside and outside Iran, and the local and regional synoptic conditions governing dust production centers is the cause of changes in the spatio-temporal patterns of dust storms. The unprincipled extraction of water resources by humans, land degradation, soil moisture reduction, and the loss of vegetation due to climate change all affect these factors in turn. The results showed that the monitoring of monthly average AOD changes can help to identify new hotspots and evaluate the results of wind and dust erosion control and management activities. Therefore, it can be suggested that a system based on remote sensing must be designed and presented to monitor dust changes, so that the management of the dust phenomenon in Iran becomes more. We need to pay attention to the factors that influence these changes and evaluate their impact on the dust phenomenon.  On the other hand, by modeling the environmental factors affecting on the trend of dust changes in each region by using methods such as dust evaluation, it is possible to determine the role of each factor and the most important factor affecting the trend of dust changes in each region.

The growth of plants is affected by environmental stresses, particularly drought and salinity, which are the main problems of arid and semi-arid lands. Germination is a crucial stage in the life of most plants. Plant establishment in arid and semi-arid regions requires special tolerance to stresses like salinity and drought during the germination stage. In most plants, increasing salinity and drought stress during the germination stage prevents the plant from germinate. Therefore, knowing the resistance to salinity and drought in different plants can be used in the management of natural environments. Considering the increase in global temperature and the decrease in rainfall in Iran, as well as the soil salinization, it is very important to choose plants with high tolerance to salinity and drought in rangeland. In the southern rangeland of Kohgiluyeh Va Boyer Ahmad province, which are located in arid and semi-arid climates, non-native species such as Atriplex spp. and Prosopis spp. have been used for improvement and restoration in the past decades. The soil and native vegetation of the region are negatively impacted by non-native plants, which have problems like lack of natural regeneration. Identifying suitable native plants that can grow in specific ecological conditions of arid and semi-arid areas, such as drought and salinity, is necessary. The current research aims to identify native resistant species to the mentioned stresses for vegetation restoration in biological and bio-mechanical projects.

In order to identify the species tolerant to environmental stress in the rangeland of Kohgiluyeh Va Boyer Ahmad province, three native species including Zygophyllum eurypterum Boiss. & Buhse, Sanguisorba minor L. and Salsola orientalis S. G. Gmelin (Salsola rigida) were selected. The habitats of the species were identified through field surveys and the cooperation of experts from the General Department of Natural Resources and Watershed Management of Kohgiluyeh Va Boyer Ahmad province. Sampling of plant seeds for experiments was done in range habitats. Seed germination reaction of three species Z. eurypterum, S. minor. and S. orientalis were studied in the laboratory with respect to different levels of salinity and drought stress. The drought stress test included six levels (0, -0.3, -0.6, -0.9, -1.2, and -1.5 MP) which were prepared using polyethylene glycol 6000. The second experiment included 6 salinity levels (0, 50, 100, 150, 200, 250 mM). Sodium chloride was used to create salinity stress. Before conducting the salinity and drought tests, treatments were applied to break the seed dormancy of different species, and after identifying the best treatment for each species, dormancy tests were performed. Germination was done as a factorial experiment in a completely randomized design with 4 replications (20 seeds per replication) in a germinator at a temperature of 25°C. During a period of 20 days, every day the germinated seeds whose root length was more than 2 mm were counted and their germination percentage, germination rate, length of root, stem and seedling and their seed germination index were measured. Using SPSSVer.23 software, analysis of variance and comparison of average data was done.

Variance analysis shows that there is a significant difference between drought and salinity levels in the traits measured in plants (p<0.01). There is a significant difference between plant species and drought-salinity interaction and species(p<0.01). With the increase of dryness, a significant difference was observed in terms of germination percentage in all three species. In this condition, the highest amount of measured traits including, germination percentage and seed germination index was observed in Z. eurypterum. with increasing salinity, the germination rate of all three species decreases significantly. In the condition without salt stress (control treatment), the highest percentage of germination (77%) was obtained in S. minor. But with increasing salinity levels, the highest germination percentage is observed in S. orientalis, and also with increasing salinity levels, the lowest germination percentage is related to S. minor species. Plants responded differently to environmental stresses, as shown by the results in general. The restoration and improvement of rangelands requires knowledge of plants that are resistant to existing stresses in order to manage natural areas. According to the current research, the rate of germination and growth of seedlings decreases as salinity and drought levels increase. Among the studied species, Z. eurypterum is the most resistant to drought and S. minor is the most sensitive. It can be concluded that the highest germination is observed in S. orientalis, when salinity levels increase, and the lowest germination is observed in S. minor species. Therefore, S. orientalis can be considered as a salt resistant. As the species studied are indigenous and native in the south of Kohgiluyeh Va Boyer Ahmad provinces, the results of this research are suggested for use in biological projects.

One of the environmental challenges in the world is desertification. Desertification is land degradation in arid, semi-arid and dry sub-humid caused by several factors such as climate change and human activities. Desertification is a significant phenomenon, particularly in arid and semi-arid regions. In many instances, it is seen as a serious threat to human societies. The desertification process in developing countries is very intense, and this issue can have a significant impact on the future of these countries. Iran is a country that is exposed to the phenomenon of desertification. Due to the geographical location, arid and semi-arid areas cover approximately two-thirds of Iran.  The desertification phenomenon is present in Yazd province. Due to its climate and hydrogeomorphology, this province, which is located in the central regions of Iran, has a high vulnerability potential against land use changes and desertification. Considering the importance of the topic, this research has identified the vulnerable areas of Yazd province against desertification using the DVI index.

In this research, library information, statistical data related to the population of Yazd province, climatic data of Yazd province, as well as the 30-meter SRTM DEM as the most important research data were used. The model used in this research was based on DVI vulnerability index. The DVI vulnerability index was the basis for the model used in this research. The time-spatial changes of vulnerability to desertification in the Banas River basin in India have been investigated using the DVI model. The DVI model uses 9 indicators, which are grouped into 4 groups: demographic indicators, weather indicators, topographic indicators, and soil indicators.

In this research, in order to identify the vulnerable areas of Yazd province to desertification from demographic indicators (population density, population growth and illiteracy percentage), weather indicators (precipitation rate, average temperature, and evaporation rate and dryness index), topographic indices (slope percentage) and soil science indices (soil type) have been used.The slope index indicates that the western parts of Yazd province are more vulnerable. According to the geological index, the northern and eastern parts of this province are highly vulnerable. The northern, central, and eastern regions of Yazd province are highly vulnerable in terms of precipitation, average temperature, evaporation, and dryness indicators. Yazd city has a high vulnerability potential in terms of population density index. In terms of population growth index, Ardakan city has a high vulnerability potential and also in terms of illiteracy index, Taft city has a high vulnerability potential. The location of Yazd province has resulted in a large portion of its area being covered in arid and hyper-arid areas. Due to their high vulnerability to erosion, destruction, and vulnerability, many parts of this province are prone to desertification. The DVI model was used to evaluate the vulnerability potential of Yazd province against desertification in this research. The DVI model results are divided into 4 vulnerability potential classes: low, medium, high, and very high. The results indicate that the class with a high vulnerability potential covers 42.9% of the area, which is primarily concentrated in the northern and central areas of Yazd province. The class with high vulnerability potential covers 41/4 of the area, which primarily encompasses the western regions of Yazd province. The classes with medium and low vulnerability potential are distributed in the central, southeastern, and southern parts of Yazd province, with 14.3 and 1.4 percent of the area, respectively. The vulnerability status of cities in Yazd province has been assessed in this research. Khatam and Bahabad cities have the lowest vulnerability percentage, while Yazd, Meibod, and Ardakan cities have the highest vulnerability potential, according to the results. Many parts of Yazd province, including its northern and central regions, have a high vulnerability potential, which requires special attention and the implementation of long-term programs to prevent vulnerability and increase desertification.

Widespread lands in arid, semi-arid, or dry sub-humid areas of the world have been influenced by the consequences of the land degradation resulting from natural factors and human activities like agriculture, changes in the land use. A large part of Iran is located in arid and semi-arid regions. The degradation of soil can be greatly impacted by agricultural activities, incorrect management, and improper land management. The most suitable solution to reduce the negative effects of land use change on the desert is to choose the best type of land management with the least degradation. The fragile nature of these ecosystems and the large area of arid and semi-arid areas of the country require proper and accurate management. Soil is an important and valuable terrestrial source of OC storage, which plays a significant role in the global C cycle by storing about 1500 billion tons of C. The total C in microbial biomass is 1.4% of the total SOC. demonstrating the significant contribution of this sector to the global C cycle. Land use change can be one of the most important factors of land degradation that affects the quality and quantity of soil organic C, and soil characteristics. The present study was done to investigate the role of different land uses including rangeland as control, abandoned land, Triticum aestivum L. cultivation, Hordeum vulgare L. cultivated lands and Medicago sativa L. cultivation, on some soil microbial indices such as basal soil respiration, substrate induced respiration, microbial biomass carbon, microbial biomass nitrogen, microbial quotient, metabolic coefficient and carbon access index, in Lasjerd , Semnan province in two depths  of 0 to 10 cm and 10 to 30 cm.

The initial step was to select various treatments that included rangeland as control treatment, abandoned land, Triticum aestivum cultivation, Hordeum vulgare cultivated lands and Medicago sativa cultivation. In the second step, soil sampling was performed at two depths of 0-10 and 10-30 cm in five replications. In this regard, one soil profile in the center and four other profiles were dug in the form of a cross, considering the marginal effect. The samples needed for soil biological tests were carried and stored in the refrigerator containing dry ice and biological tests were performed later. The considered factors were measured by valid scientific guidelines and methods. Data related to soil microbial properties were analyzed by a factorial test in the form of a completely random design with five repetitions. All statistical computing was done using SPSS 19 software and the mean comparison tests were performed by Duncan test.

The results of the present study indicated that there is significant impact of the treatments on the properties studied at the two depths, at the first soil layer equals to the depth of 0 to 10 cm, basal soil respiration, substrate induced respiration, microbial biomass carbon, microbial biomass nitrogen, microbial quotient, and metabolic coefficient have been affected by different land uses, as the highest level of basal soil respiration in the abandoned land equals to 0.424 mgCO2g-1dm24h-1 and the lowest in Triticum aestivum cultivation 0.006 mgCO2g-1dm24h-1, as well as the second depth- 10 to 30 cm- basal soil respiration, microbial quotient, metabolic coefficient are affected by different types of land uses. The highest amount of metabolic coefficient was observed in abandoned lands as 0.068 mgCO2 C1MBCday-1 and the lowest was found in Medicago sativa cultivation lands equals to 0.013 mgCO2-Cg-1MBCday-1. Soil microbial indices are sensitive to land use changes. The first top 10 cm of the soil studied, has been most affected by these indices. Due to the failure of soil pedons, the change in land use from rangeland to agricultural lands increases the speed of litter decomposition and decreases the storage of soil nutrients, the microbial population, composition and activity of the soil as an indicator of soil quality, health and fertility. But techniques of no-tillage or minimal-tillage, as well as the principles of sustainable agriculture (such as returning the residues to the soil, proper use of chemical fertilizers, using biological fertilizers, and biological control of pests) cause the destructive process of the biological indices to be adjusted and get balanced in a shorter time period with environment. Considering the changes in the biological indicators of the soil, which have caused the destruction of the cultivated lands in the studied area, it is suggested to rehabilitate the bare lands with native rangeland species of the region, such as Artemisia sieberi Besser, Zygophyllum eurypterum Boiss. & Buhse, and Astragalus tribuloides Delile. Range management plans are the only way to allocate rangelands in the region, and a detailed survey of rangelands in the region is necessary. To prevent land use change, it is important to address the multi-purpose uses of rangelands and the determination of economic units to support the lives of beneficiary households.

Marl formations are one of the most important sources of sediment production in arid and semi-arid regions. Marl lands are highly susceptible to erosion, causing an increase in drinking water treatment costs, reducing the useful life of dams, and significantly decreasing the permeability of floodwater spreading areas.  Different forms of erosion have been shown to have a relationship with the geological characteristics of marls, as evidenced by research. The results of the study of the effect of the physical and chemical properties of marl sediments on erosion in Latshore-Pakdasht showed that the amount of Na+, SO4-2 and silt in the marl lands increased, while the percentage of clay decreased from surface to gully erosion. The form and intensity of water erosion are greatly influenced by changes in soil texture. Gully erosion can be developed by increasing the amount of sand compared to the finer particles of silt and clay. Despite the difficulty of vegetation establishment on marl lands, in some areas, surprisingly, a relatively dense cover of rangeland species can be observed, which can cause erosion control and soil stability. The results of the systematic survey of plant species and their protective role in the marl lands of Ilam, Yazd and Gilan provinces all indicate that rangeland species are one of the most effective and suitable methods to prevent soil erosion by creating a stable vegetation cover on marl formations. The relationship between the physical and chemical properties of the soil with vegetation characteristics including distribution, canopy cover and density is inevitable. In the marl lands of Borujen, the research revealed that vegetation type named Astragalus brachycalyx-Daphne mucronata-Cirsium bracteosum can be established in neutral marl lands, with medium CaCO3 content and minimal presence of Na+ and Cl-. On the other hand, the vegetation type named Astragalus susianus-Daphne mucronata-Amygdalus elaeagnifolia can be established in alkaline and calcareous marl lands with very high amounts of Cl- and can be effective in controlling water erosion in marl lands. Considering arid and desert climate and the occurrence of surface, rill and gully erosions in the marl lands of Kashan region, as well as the importance of protecting and controlling erosion in the marl formations of the region and the lack of detailed vegetation studies in this region, accurate identification of the vegetation of the marl lands and prioritizing native and resistant plant species is necessary for the rehabilitation management of vegetation and biological protection of soil in these areas. Therefore, the aim of the current research is to identify rangeland species and investigate their role in erosion control in the selected marl formations in Kashan. In addition, the physical and chemical soil parameters of marl lands and the vegetation characteristics of plant species in different types of erosion are investigated.

Kashan is one of the marl regions chosen for the current study on the classification and determination of marl erodibility indices in Isfahan province. Two vegetation types named Anabasis setifera-Artemisia sieberi-Salsola tomentosa and Pteropyrum aucheri-Pteropyrum olivieri-Artemisia sieberi have been identified in the selected Marl lands of Kashan. In order to evaluate the erosion condition in three erosion forms of surface, rill and gully, BLM (Bureau of Land Management) form was completed in the same marl units and control areas without vegetation cover. In the next step, three soil samples were collected from 0-20 cm depth in three repetitions in marl units including three forms of erosion. The physical and chemical soil properties including texture, EC, N, P, SAR, OC, CEC, CaSO4 and CaCO3 were measured. For vegetation studies in the study area, after preparing the floristic list of plant species, three 100 m transects were established in a random-systematic method. In each transect 10 plots of 2 m2 were placed and vegetation characteristics including canopy cover percentage and density per plant species, as well as the percentage of gravel and litter were measured and recorded. The statistical analysis of the data was done as a completely random design using SAS software, and the averages of soil properties were compared according to the Least Significant Difference (LSD). Correlation analysis between soil and vegetation characteristics was done by SPSS statistical software.

The results showed that in terms of erodibility, Marl lands with vegetation cover had a better condition than those without vegetation. Based on analysis of variance, the physical and chemical parameters of soil and vegetation characteristics in three types of erosion had significant differences at level of 1% and 5%. In gully erosion, the amount of N, P, SAR, OC, litter and canopy cover were in better conditions compared to other types of erosion. The results of correlation between soil properties and vegetation characteristics showed that the canopy cover had significant correlation with the percentage of sand (r=0.92) and a negative correlation with the amount of CaCO3 at (r=0.97). In terms of the type of dominant plant species, in surface erosion Ephedra strobilacea Bunge. with canopy cover of 1.71%, in rill erosion Anabaisis setifera Moq. with canopy cover of 1.24% and in gully erosion Artemisia sieberi Besser. with canopy cover of 12.3% were identified as the most suitable species for soil protection. In all three types of erosion, bushes had the highest percentage of density in terms of growth form. In surface erosion and gully erosion, shrubs occupied the highest percentage of canopy cover.  In gully erosion, due to better conditions of soil moisture and organic matter, bushes and shrubs were successful in competition with annual and herbaceous plants. They established well due to deep and extensive root system. The results of current research could be considered as a novel achievement in order to prevent soil erosion through establish appropriate species in marl lands with similar climatic conditions.

Sand covers around 20% of the world's drylands, and 97% of it is found in the sandy land of the arid region of the earth. Different landforms are created by the wind in these regions. Sand dunes are a landform that is mentioned in arid lands. Knowing the distribution of sand in these areas is crucial because wind erosion can cause a lot of damage. The significance of studying sand dunes lies in its impact on water and soil resources, plants and animals, human infrastructure, and roads. In Iran, various researchers and related organizations have reported various areas of the sand dunes. Different tools and methods have been utilized by these researchers, including aerial photos, topographic maps, satellite images, and field visits. This study was conducted to improve accuracy and update the existing maps due to the differences between the maps provided by previous researchers. By providing a new map of sand dunes distribution in Iran, more precise information can be obtained. Precipitation, temperature, evapotranspiration, and UNEP aridity index were used to calculate climate characteristics for Iran's sand dunes.

Remote sensing was used to export the sand dunes distribution map in this research using the Google earth engine system. The image collection of the OLI sensor of the Landsat 8 satellite was used. The process of image classification involved introducing 4000 points as training points. The land use map of Iran was exported after verifying and calculating the overall accuracy and kappa coefficient, which were 0.91 and 0.89, respectively. The map's sand dune class was imported into ArcMap. The maps of the distribution of sand dunes obtained from previous researchers were compared with the obtained map. The boundary of sand dunes was modified by drawing 1020 polygons using vision recognition. We aim was always to utilize the most up-to-date satellite images for visual interpretation. Due to differences in tools and study time, and the prepared maps based on different criteria, there are numerous differences between the maps in practice. The research utilized up-to-date satellite images and geological maps, topography, hand-planted forests, residential lands, agricultural lands, and land use as auxiliary maps. In the next step, the long-term climate maps prepared by Jamab's consulting engineers for the period of 1350 to 1390 were used to investigate climate characteristics such as temperature, precipitation, evaporation and transpiration and UNEP aridity index. The mentioned maps were interpolated and classified in ArcMap for this purpose. The distribution of the country's sand dunes was examined in each of the categories mentioned in the climatic indicators.

Based on the result, the updated area of Iran's sand dunes is 5.15 mha which includes the sand sheets and different forms of sand dunes such as barchans, star dunes and nebkas. Based on this, the provinces of Kerman, Sistan and Baluchistan, Isfahan, South Khorasan and Yazd respectively, with an area of about 1000000, 700000 and 590000 ha, have allocated the largest area of sand dunes in the country. There are some differences in the obtained results compared to the previous maps of sand dunes. In Dehlran city in Ilam province, some regions that were previously considered sand dunes have now become agricultural lands, for instance. The border modification resulted in a 366% increase in the area of Qaen city in South Khorasan province. According to climate data, sand dunes are distributed in three climates that are hyper- arid, arid, and semi-arid. The highest and lowest amount of precipitation can be found in Farashband city in Fars province and Hirmand city in Sistan and Baluchestan Province, respectively. The range of precipitation changes is ranging from 6 to 312 mm.  The hottest sand dunes are located in Shahrud city in Semnan province and the coldest sand dunes are located in Buin Zahra city in Qazvin Province. The temperature of sand dunes is in the ranges of 10 to 28.5 °C. the dominant thermal regime of sand dunes is thermic, which covers about 68% of the sand dunes in 8 provinces. Hyperthermic thermal regime dominates 31% of sand dunes in 7 provinces. Only about 1% of sand dunes have mesic thermal regime which are scattered in 3 provinces. The range of changes in evapotranspiration in the sand dunes of Iran is between 1500 to 4000 mm per year. Evaluating the UNEP aridity index showed that 89% of the sand seas are classified as hyper arid and 11% of them is in arid class. The result of this research by determining the location of sand seas and their climate classification, will help the administrators to locate appropriate areas for reclamation and wind erosion control projects, especially the biological project.