نشریه مهندسی اکوسیستم بیابان
پیاپی 33 (زمستان 1400)

As one of the most serious environmental challenges of Iran during the recent decade, the phenomenon of fine dust has occurred due to improper and excessive ecologic use of rangeland ecosystems, drought, and mismanagement of water resources. Knowing this phenomenon and being aware of the required strategies to fight against it play an essential role in reducing the number of dust storms and the way fine dust's hotspots are established. On the other hand, the hotspots of fine dust have been created in large areas of Urmia Lake's saline lands due to the regression of the lake made by a decline in groundwater levels and reduced inflow of water into the lake exposing Western and Eastern Azerbaijan provinces to dust storms. Accordingly, some restoration projects (rangeland seeding) were carried out in 2014 in large areas of the lake to stabilize the soil of the hotspots' beds. Now, five years after the implementation of rangeland seeding projects, the question is whether or not the projects have exerted any positive effect on the structural and functional characteristics of the target habitats? In other words, how have the structural and functional characteristics of the habitats changed as a result of rangeland seeding operations? Have these changes had positive or negative effects on the ecosystem? Therefore, to answer these questions, this study was conducted in the Separghan region in Urmia as a pilot study area and a representative of saline habitats of the western shore of Urmia Lake. Located at 37° 45' 14"N and 45°14'19", the region was identified as one of the fine dust hotspots in 2014 and designated as a priority in terms of protective and conservation operations by competent authorities. It was also introduced as a reference and pilot study area so that the results of the study could be generalized to similar habitats. Therefore, rangeland seeding operations were carried out in the region at a large scale where livestock grazing was prohibited.

24 transects were established in three ecological areas to measure the structural and functional characteristics of the habitats. Moreover, the number, length, and width of ecological patches, the percentage of patches' lengths, and the landscape organization index were calculated for each area by establishing linear transects in each ecological unit. Finally, eleven indices regarding the soil's surface that are clearly associated with the soil's level of stability, permeability, and nutrient cycle were valued and categorized for each patch and inter- patch space within the five measured areas using the LFA guidelines.

the study's results indicated that the indices' mean varied along the salinity gradient, being significantly different in various ecological areas. The highest value of the landscape organization index (0.32) belonged to the first area (further away from the salinity hotspot), and the lowest values of the index (0.10 and 0.06) belonged to the second and third areas (closer to the salinity hotspot), respectively. The average values of the stability index were 44.40, 37.01, and 20.70 in different ecological zones, respectively. Furthermore, the highest values for permeability were found in the first and second zones as 21.50 and 24.90, respectively, and the lowest index's value (13.20) belonged to the third zone. Finally, the values of the nutrient cycle were 11.19, 11.80, and 7.90 in the first, second, and third ecological zones, respectively.

it could generally be argued that the values of structural and functional indices decrease along the salinity gradient. Therefore, the success of rangeland seeding operations would decrease as we get closer to the salinity hotspot. In other words, rangeland seeding operations have failed to realize the goals set for the first step of its executive operation to increase vegetation and reduce inter-patch spaces in areas close to the lake. Viewed from another perspective, it can be concluded that seeding the rangeland with Nitraria schoberi species was hardly successful and failed to achieve its expected results in terms of controlling the fine dust several years after the implementation of the project. Therefore, preserving the area and less manipulating the soil's surface is recommended when rangeland seeding is conducted in such habitats. If prevented from being grazed, indigenous vegetation could be regenerated through the seed bank and thus help prevent soil surface from wind erosion. The results of this study can help seed the rangelands prioritized for being protected against the advancement of saline dust hotspots. The areas prioritized in terms of protection and maintenance of their current situation are those with high structural and functional indices values. Areas where the inter-patch space is large and the landscape organization index is very low compared to other places can also be prioritized for restoring projects.

Wind erosion and thunderstorms bring about significant adverse consequences, including air pollution, reduced visibility, wear and tear of industrial machinery, soil structure destruction, and adverse effects on soil fertility. In recent years, the aerosol pollution caused by sand storms has turned into a serious health threat for Iranian people. In addition to being detrimental to human health, the adverse consequences mentioned above will also cause many problems for ecosystem processes. That is why the fight against erosion has received worldwide attention. The application of mulch is a method widely used to control wind erosion and stabilize sand grit and dust hotspots. Mulch is defined as any natural and artificial material that is promoted and applied to the soil surface together with crop residues, plastic films, asphalt, emulsion mulch, oil, petroleum residue, nano-clay matters, and livestock manure. Therefore, this study sought to examine the chemical properties of soils covered by two emulsion mulches.

This experimental study was conducted in some parts of large desert areas located in Aran and Bidgol counties. The treatment items examined in this study were the type of mulch, time of mulch application, and soil depth. In addition to harvesting soil samples covered with mulch, control soil samples were also collected for comparison. PH, EC, concentration of cations (Ca, Mg, K and Na), and anions (NO3, HCO3, SO4, Cl) were other parameters examined in this study.

The results showed that the application of emulsion mulch reduced the soil's pH and EC. In fact, reducing soil salinity leads to a decrease in soil cations and anions concentration, providing suitable conditions for plant growth and establishment by maintaining moisture and reducing evaporation. It was also found that moisture in soils covered by emulsion mulches was significantly higher than that of the control soil during the study period (12 months), reducing the concentration of cations. Considering the fact that the presence of emulsion mulch in the soil surface leads to a decrease in its concentration of cations compared to that of the control soil, this study's analysis of the dominant sodium cation in soil showed a significant decrease in treatment mulch compared to that of the control mulch. Moreover, the concentration of chlorine and sulfate anions was found to have decreased after the application of emulsion mulch, resulting in the creation of suitable conditions for plant cultivation in the region. In contrast, the study found that bicarbonate concentration in the soil increased due to the presence of carbon in the emulsion mulch structure compared to that of the control soil sample.

There was a significant decrease in the amount of salinity in the soil treated with both types of mulch compared to the control soil that received no mulch, the amount of which increased over time. The main reason for the reduction of salinity in the soil treated with the two types of mulch could be the reduced water evaporation from the soil surface caused by an increase in the soil's moisture. Code 1 emulsion mulch was more efficient in maintaining the soil moisture than the other type of mulch. Increasing moisture affects the soil's aggregation by increasing the adhesion between particles and, therefore, the velocity of wind erosion threshold will be decreased. Furthermore, the study found a decrease in the pH of the soil covered by mulches. This decrease in pH was more evident in surface samples, indicating a relative decrease in pH than that of the subsoil.As soil salinity decreases after mulch application, the concentration of cations is also expected to decrease. Among the cations examined in this study, the soil's dominant sodium cation suggested a significant decrease in treated emulsion mulch compared to that of the control mulch. Possessing a lower sand percentage, Code 2 emulsion mulch was found to have a more decreasing effect on the cation concentration after 12 months of its application. The study's results also revealed a reduction in the concentration of all studied cations, which occurred 12 months after the application of Code 2 emulsion mulch, while the concentration of the cations had not changed after six months of the application of the mulch.  The study also found that chlorine and sulfate anions significantly reduced in the studied anions of the treated soils. The final results of this study suggested that both types of applied mulch could contribute to reducing the effects of harmful cations and anions on plant growth and that the application of the mulches would allow more plants to be grown in such areas. Moreover, the results of long-term tests showed the efficacy of the two applied mulches in terms of their stability.

Salinity is a basic non-living environmental factor that reduces the yield worldwide. In arid and semi-arid regions, the salinity of water and soil limits crop production. Therefore, it is crucially important to assess the salinity tolerance of medicinal herbs if they are to be cultivated in saline areas.

To investigate the effect of water salinity and some saline organic fertilizers on the lemongrass' (Cymbopogon citratus) physiological features and growth, a greenhouse experiment was carried out in the research greenhouse of Hormozgan Agricultural and Natural Resources Research Center through a completely randomized design with four replications at seven salinity levels including non-saline water as a controlling factor, saline water at 4, 10, and 15 ds/m levels, and saline organic fertilizers at three levels including fish meal fertilizer with salinity rate of 5/2, liquid fish manure with salinity rate of 4/9, and poultry slaughterhouse fertilizer with salinity rate of 4/6 ds /m. Moreover, the physiological growth features, including the leaf area, the leaf's fresh and dry weight, the root's fresh and dry weight, the plant's height, the number of tillers, and total chlorophyll were investigated.

The study's results indicated that water salinity and organic fertilizers had a significant effect on all studied features. It was also found that treating Irrigation water with a salinity of 15 ds /m had the most negative effect on all studied features, with the root's dry weight affected the most. On the other hand, treating poultry slaughterhouse fertilizer with a salinity of 4/6 ds/m improved all physiological growth features compared to the control factor except the number of tillers per plant. The results also showed that lemongrass was sensitive to over 5 ds/m salinity but tolerated less than 5 ds/m salinity and that it was possible to use the relatively saline organic fertilizers studied as a food source in cultivating this plant.

Desertification refers to the decreased biological potentials in the ecosystem of hyper-arid, arid, semi-arid, and humid semi-arid regions because of climate change and human activities. The phenomenon occurs due to a combination of direct and indirect factors whose intensity varies according to time and place, making the scientific, replicable, and systematic evaluation of desertification an essential task. Remote sensing technology which is based on spatial information collected at regular intervals by aircraft and satellites plays a prominent role in assessing and monitoring land degradation and desertification on a local, regional and global scale. On the other hand, Change Detection is a process that evaluates spatial changes in various phenomena caused by natural and human factors, using multi-time satellite images. As an effective method for detecting and describing land cover changes, the change vector analysis method provides information on spectral changes in terms of magnitude and direction. Therefore, considering the significance of determining the intensity of desertification in different parts of Iran and evaluating methods for investigating the changes in desertification intensity, the present study sought to evaluate desertification using the change vector analysis for different land-uses of the Gavkhoni basin.

This study used the change vector analysis (CVA) method to determine desertification changes in the Gavkhooni basin based on algorithm-driven classification, producing two components of magnitude and the direction of change. Moreover, to evaluate the intensity of desertification via the change vector analysis method, EVI and BSI were used for examining the study area's vegetation and bare soil. Possessed with 13 layers to assess the land use, the MCD12Q1 product with annual temporal resolution and spatial resolution of 500 m was used as a Level-3 network product in the sine image system to evaluate the land use. In addition, the IGBP standard was also used to assess land cover and land use.

The results of analyzing the changes made in the BSI during 2001-2005 and 2000-2016 indicated that throughout the latter period, BSI values decreased in central, western, northwestern, eastern, and southeastern regions of the study area. On the other hand, the results of analyzing the changes in the EVI revealed that during the same period, the index values increased in the west and northwest of the region, while the index value decreased in the eastern, southern, and southeastern parts of the region. Moreover, the results of analyzing the changes in desertification showed that the number of changes in some areas of the center, west, southwest, and southeast of the region was greater than other areas, which could be attributed to rehabilitation or destruction in the study area. The results of analyzing desertification-related changes in terms of direction suggested that the intensity of destruction in the center, south, east, southeast, and northeast of the region was higher than that of other regions. The rehabilitation has occurred in the northern, northwestern, and southwestern regions. Among the areas that were under rehabilitation process, 14.15%, 12.04%, and 10.31% of the basin area were found to be in the low, medium, and high rehabilitation classes, respectively. On the other hand, in terms of the extent of destruction in the region, 12.02% of the study fell under the medium destruction class, while 8.24% and 8.91% of the study area were placed under the low and high degradation classes, respectively. However, 34.33% had remained unchanged in terms of desertification status. According to the results of analyzing the intensity and direction of changes in each land use, 0.42% of agricultural lands were found to be in the high destruction class. Furthermore, the greatest percentage of high rehabilitation class belonged to grasslands, which covered 5.40% of the study area.  However, 28.5% of the area which comprised of barren lands was divided under the trend-free class. It was also found that 1.88% of non-dense shrubs and 0.36% of residential lands were under the high destruction class.

As desertification is among the serious ecological crises in today's world, it is necessary to well identify and recognize the causes and processes involved in desertification on a regional and global scale. Therefore, this study used the vector analysis method to evaluate the desertification status in different land-uses of the Gavkhoni basin. The multivariate CVA technique was used in the pixel-by-pixel analysis of bands or spectral indices. The changes that occurred throughout two different periods (as mentioned earlier) were identified by placing the quantitative value of the pixels on the two axes of the Cartesian plane, out of which two componential elements, i.e., magnitude and direction were obtained.In general, the results of the present study indicated that while the east and center of the Gavkhoni basin were in a state of destruction and desertification, the bare soil in the western and northwestern regions of the Gavkhoni basin had been replaced by vegetation due to agricultural activities and cultivation and that these regions were in a state of rehabilitation. Therefore, the vector analysis model is recommended to be used for analyzing changes in other basins. In fact, unless a more accurate and better evaluation model is introduced, this model could be used confidently to assess the severity of future desertification.

Dust storm is a major weather event that plays an important role in the Earth’s atmosphere and ocean surfaces. Dust storms affect marine phytoplankton, soil physical and chemical characteristics in entrainment and deposition areas, climate and radiative forcing, economic loss, and human health. They mostly originate from Introduction Dust storm is a major weather event that plays an important role in the Earth’s atmosphere and ocean surfaces. Dust storms affect marine phytoplankton, soil physical and chemical characteristics in entrainment and deposition areas, climate and radiative forcing, economic loss, and human health. They mostly originate from plains and playas across North Africa, the Middle East and Asia. One of the main sources of dust is relatively recent flood sediments deposited since the late tertiary. Asia, with approximately 60% of the population of the world, is an important source of dust that impacts the climate on a global scale. A dust storm is defined by the World Meteorological Organization (WMO) protocol as where ‘strong winds lift large quantities of dust particles, reducing visibility to between 200 and 1000 m’. Therefore, the aim of present study was to investigate the potential of desert dust mapping algorithms using satellite images in the west and western parts of Iran.

The study area has hot and arid climate; therefore, dust storms are usually occurred especially during dry seasons in this region including Iran, Iraq, Syria, Jordan, Kuwait, Saudi Arabia, Bahrain, Qatar, UAE, Oman, and Yemen. Although, some of dust in the study area comes from the Sahara in the Africa. In recent years, the most environmental problem in Iran is the dust crisis in the western half of the country in mountainous regions of Zagros. Zagros Mountains occupy a broad extent of western Iran, covering an area roughly 1300 km by 200 km. The mean annual rainfall is from 400 to 800 mm and mostly in the winter and spring. The average annual temperature ranges between 9°C and 25°C. The most common ecosystems in the region are the forest and semi-steppe areas. Forests with an area of 5 million hectares cover about 40% of Iran’s forests and are the widest forest regions of the country. This region with its semi-arid climate is generally dominated by broad-leaved trees with the dominant species of Quercus brantii that covers more than 50% of Zagros’ forest area. Dust storms from western neighbouring countries such as Iraq have significantly increased in recent years and much of Iran is affected. For example, 20 and 52 dusty days in 2008 with visibility less than 1000 m occurred in Somar and Abadan meteorological stations in Kermanshah and Khozestan provinces, which are the nearest stations to Iraq. Around 31% of Iraq’s total land is desert, which is the main source of soil-derived mineral dust in the region. There are three important sources of dust storms in Iraq: one is centred over Baghdad; the second is centred west of Basrah; and the third is the Southern Desert. Thus, dust cases are common in central and southern Iraq. The major hotspots for dust generation are aeolian deposits south of Baghdad, Karbula, Najaf, Nasiriya, Basrah, as well as Kuwait, and also alluvial deposits of Tigris and Euphrates Rivers from sandy clayey silt (72%) to clayey sandy silt (28%). In addition to the high potential of Iraq’s desert deposits for dust production, recent changes in the region such as war in Iraq, dam construction in Iraq and neighbouring countries, and intense drought conditions have increased the frequency of dust events. Saudi Arabia is rich in fine sediments from dry riverbeds and lakebeds and sand seas, and is another important dust source in the region. Therefore, for mapping this environmental crisis, MODIS level 1 B satellite images were acquired in winter and summer seasons and processed with MCT tool. Then, the BTD, Ackerman, Miller and TDI algorithms were applied to the images and dust regions were mapped with use of appropriate thresholds. The accuracy of the outputs maps were assessed against natural color composites and dust products including Aqua AOD and Aura AI.

Results showed that a single method for identifying different dust plumes cannot be used due to differences in mineralogy and weather conditions of the events and each algorithm needs different threshold based on the event type and characteristics. The algorithms worked best on dense dust, but they performed differently in cloudy regions and over bright desert surfaces. Most of the algorithms examined here misidentified thick cloud cover as dust. Despite the published dust/no-dust thresholds for the methods tested here; results indicated that it was not possible to use a single dust/no-dust threshold for any of the algorithms applied to the studied events. Therefore, it seems that for each dust event an event-specific threshold is needed.

Comparison of the studied algorithms showed that all of them produced almost similar results and, among them, the TDI index had relatively better performance over dust sources and showed its usefulness as an effective approach for dust detection and mapping in the region. It appears that the combination of these simple algorithms is the best way to overcome the limitations of different dust detection methods. By combining several algorithms used in this study, the performance of dust detection and mapping may improve. The finding indicated that free and available dust products are sufficient for assessment and monitoring dust storms in Iran if the maps less than 10 km are not required.plains and playas across North Africa, the Middle East and Asia. One of the main sources of dust is relatively recent flood sediments deposited since the late tertiary. Asia, with approximately 60% of the population of the world, is an important source of dust that impacts the climate on a global scale. A dust storm is defined by the World Meteorological Organization (WMO) protocol as where ‘strong winds lift large quantities of dust particles, reducing visibility to between 200 and 1000 m’. Therefore, the aim of present study was to investigate the potential of desert dust mapping algorithms using satellite images in the west and western parts of Iran.

Climatic components are the vital factors influencing the dust event. It was believed that changes in climate parameters play a crucial role in the occurrence of dust events. Former studies have shown that temperature, rainfall, and wind speed contribute to poor vegetation, providing requirements of dust events. Long-term dust data indicated that climate has a profound effect on dust events and the occurrence of dust storms compared to the desertification process (Zhang and Anastasio, 2003). Monitoring Iran’s meteorological data indicates changes in precipitation and temperature in the last two decades (Rezaei and Ghasemieh, 2019). Alterations in the amount and pattern of rainfall and rising temperature can initiate the changes that cause natural hazards, including dust storms. Hence, in the present study, the trend of changes in climatic parameters in Khorasan Razavi province has been investigated. Note that the climatic parameters are consisting of rainfall, average temperature, wind speed, and frequency of erosive winds.

 According to the objectives of the present study, the monthly precipitation, temperature, and wind speed of seven synoptic stations including, Mashhad, Sabzevar, Sarakhs, Neishabour, Torbat Heydariyeh, Kashmar, and Quchan, were obtained from the meteorological organization of Khorasan Razavi from 1990 to 2016. Hourly dust codes also were extracted to detect the number of dusty days in the study period. The relationship between climatic parameters of precipitation, temperature, wind speed, and erosive wind frequency was inspected by the Pearson correlation coefficient for each station. Later, the trend of dust events and climatic parameters was analyzed using the Mann-Kendall trend test.

 Results of dust codes indicated the local origin for the highest frequency of dusty days. Even though Sarakhs and Mashhad stations had the highest dusty days, Quchan and Kashmar had the lowest one in the study region. The Mann- Kendall test pointed out an increase in temperature for all study stations except Neishabour. Meanwhile, the precipitation had a downward trend in the Mashhad, Kashmar, Sabzevar, Torbat Heydariyeh, and Sarakhs stations and an increasing trend in the Neishabour and Quchan. Raising the frequency of the erosive wind in Quchan, Kashmar, Sabzevar, Sarakhs, and Neishabour stations during the study period could also be stated. In most of the stations (except Mashhad and Neishabour) upward tendency in the number of dusty days is consistent with other researchers such as Mehrshahiand Nekounam (2009) in Sabzevar, Boochani, and Fazeli (2011) in Ilam, Shahsavani et al. (2011) in Khuzestan stated. Hence, the decreasing tendency of dusty days in Mashhad and Neishabour is also in line with Rafiei et al. (2015) in Yazd, Semnan, Kashan, Ramsar, and several other stations. The falling trend of wind speed in Mashhad station can be reflected as the main reason for the reduction of dust events. In addition, the rising tendency of precipitation and possible decline of drought in Neishabour can be considered as the main reasons for the decrease in the number of dusty days. To understand the effect of climatic factors on the occurrence and intensification of dust events, the relationship between the number of dusty days and climatic parameters was determined. The results of correlation analysis between dust events and climatic parameters showed that the temperature directly affects the dust events in all stations except Mashhad. The positive correlation between temperature and dust events was stated in other studies (Bahrami et al., 2013; Amgalan et al., 2017). The correlation coefficient between dust event and precipitation showed a negative relationship between them which was significant at 95% level in Sarakhs station. Other studies (Ali et al., 2016; Broomandi et al., 2017; Amgalan et al., 2017) have also indicated the inverse effect of precipitation on dust events, which is following the findings of this study. The results of correlation analysis between the number of dusty days and wind speed and the frequency of erosive wind showed that the enormous influence on dust events is wind speed. While, at Neishabour station, there is a significant negative relationship between dust and wind speed. Indeed, the inverse relationship between dust and wind speed indicates that with increasing wind speed, the dust emission does not increase and another factor reduces the effect of wind speed. As Kimura (2012) reported the impact of vegetation on reducing the wind speed impact on the dust occurrence.

 It was proven that the number of dusty days is in line with the variations of the climatic parameters. The decrease in rainfall, increase in temperature, and wind speed has been accompanied by an increase in dusty days in the region. In general, correlation analysis of dusty days and climatic parameters in Khorasan Razavi province indicated that wind speed and the frequency of erosive wind have considerable influence on dust events. However, the effect of wind speed on dust events at the Neishabour station reflected the significance of vegetation cover on reducing the transfer of soil particles.

Considering the extensive degradation of Iranian rangelands and forests due to livestock grazing and the land use change in recent decades, rangeland management requires a comprehensive knowledge concerning the ecological characteristics of native plant species and how they respond to environmental factors. Developed from the Fabaceae legume family, Taverniera spartea is an important species indigenous to the Persian Gulf and Omani rangelands of Iran. As a rich source of plant protein, this plant has a high value in feeding animals. Possessing a strong root system, the plant plays an important role in biologically stabilizing nitrogen, increasing soil's organic matter, improving soil texture, and preventing soil erosion. Lack of sufficient knowledge concerning this plant species and the relationship between soil, environmental factors, and the vegetation status is a serious obstacle to using soil for biological regeneration of degraded rangelands and planning for optimal management of existing habitats. Therefore, this study sought to investigate the response pattern of the plant to the slope of soil and topographic factors in its habitats in Hormozgan province using the generalized incremental model.

This study was conducted in Siahoo, Ahmadi, and Bashagard regions in Hormozgan province. Siahoo region is located 55 km north of Bandar Abbas at an altitude of 450 meters above sea level, Ahmadi region is located 95 km north of Bandar Abbas at an altitude of 750 meters above sea level, and Bashagard region is located 135 kilometers east of Bandar Abbas at an altitude of 600 meters above sea level. The average rainfall of Siahoo, Ahmadi, and Bashagard region is 171.54, 183.61, and 193.18 mm, respectively, and their average annual temperatures are 27.34, 25.52, and 28.6 degrees Celsius respectively. Located among the semi-humid hot regions, Siahoo region is a semi-dry hot region with the average minimum and maximum absolute temperature of 21.8 and 32.3 ° C, respectively. Moreover, Bashagard is a hot dry region with the average minimum and maximum absolute temperature of 21.1 and 33.9 degrees Celsius, respectively. A 30 plots were chosen via random-systematic sampling for each ecological unit (90 plots in three study areas). Then, the percentage of canopy cover was measured for each species located inside the plots, and a soil sample was taken from each plot for analysis. Moreover, conventional comparative analysis method was used as a nonlinear method to investigate the relationship between effective and significant environmental variables and vegetation, and forward selection was used to reduce error. On the other hand, the significance of the relationship between species composition and axes obtained from environmental variables was investigated using the Monte Carlo permutation test. Furthermore, a generalized incremental model was used to predict the response of plant species to changes in environmental factors. Finally, the Akaic information criterion was used to rank the variables affecting the performance of the species.

This study found that the soil texture was sandy loam in all three habitats. The amount of electrical conductivity in the three habitats revealed a significant difference. Soil acidity was also higher in Bashagard region than the other two ones. The highest amount of soil lime was found in Siahoo region with 54.3%, and the lowest one was observed in Ahmadi region with 19.3%. It was also found that as the soil clay percentage increased, the species response was decreased and the species presence was reduced. On the other hand, with an increase in soil acidity to 7.5%, the species response increased, and as soil acidity was increased to 7.7%, the presence of the species decreased. Also, the presence and growth of the species increased with and increase in soil acidity. The results also indicated that the presence and growth of species increased with an increase in the amount of soil lime to 55, and that the presence of the species decreased with an increase in soil lime. Moreover, as the percentage of the soil's organic carbon increased, the species response and presence increased. Furthermore, the species response and presence increased with an increase in the soil's nitrogen percentage. Also, as the percentage of uncovered soil (bare soil) increased to 55, the species response increased, and as the bare soil increased, the presence of the species decreased.

The results of conventional adaptive classification showed that seven factors, including the percentage of neutralizing material, altitude, percentage of bare soil, electrical conductivity, soil saturation, litter percentage, and soil silt percentage were the main factors which influenced the distribution of Taverniera spartea. Applying the generalized collective model with Poisson error distribution for each environmental variable showed that soil lime percentage, clay percentage, acidity, soil organic carbon content, soil nitrogen, and bare soil percentage has a significant influence at the level of 0.05%. on the species yield.The study also examined the role of the presence and yield of Taverniera spartea as a valuable rangeland species in forage production, soil and water conservation using environmental factors. It could be said that to rehabilitate the degraded rangeland areas with the required conditions for the establishment of this Taverniera spartea, the species should be planted according to its ecological needs. At the same time, proper and optimal use of the species in rangeland and suitable habitats reduces the loss of capital and time.

As a natural phenomenon that characterizes the climate system, drought exerts devastating effects on agricultural products, including reducing cultivation levels, decreasing crop yield, and changing cropping patterns, thus threatening the food security of humans and other creatures. Moreover, it brings about some social and environmental consequences such as threatening human health security, spreading diseases, increasing malnutrition, increasing the migration of rural residents, influencing the moisture, health, soil erosion, and vegetation, developing desertification, decreasing the water resources quality, increasing air pollution, and affecting groundwater reserves, wildlife, and biodiversity. These disastrous effects have turned drought into the subject of different investigations worldwide. on the other hand, as Iran is located in arid and semi-arid regions of Asia and suffers from inappropriate rainfall distribution, it faces some problems in terms of cultivating agricultural lands. Located in eastern Iran, North Khorasan province is not an exception in this regard, being considered as a region susceptible to different types of droughts, especially agricultural ones, due to its geographical location. Furthermore, recent droughts in the province have led to reduced water reservoirs' volume, severe groundwater depletion, reduced discharge of wells' water, damages to rainfed crops, and reduced irrigated crops in the province. Therefore, this study sought to investigate the relationship between drought and meteorological conditions in North Khorasan province throughout a 19-year period using remote sensing indices.

This study used the data collected from synoptic stations in North Khorasan province, and MODIS imagery data including 16-day MOD13A1 V6 products (500 m spatial resolution) to measure the NDVI index and 8-day MOD11A2 V6 products (500 m spatial resolution) to measure ground surface temperature (LST). Extracted from MODIS images in ARC GIS software, a set of remote sensing indices including NDVI, VCI, LST, VSWI, TCI, VDI, and VHI were also used to monitor the drought. Then, SPI, PNI, MCZI, and ZSI were measured to investigate the relationship between meteorological and remote sensing indices. Finally, Pearson correlations were measured between SPI, PNI, MCZI, and ZSI, and VCI, VSWI, TCI, VDI, and VHI using the SPSS software.

The results of analyzing the Pearson correlation coefficients indicated a strong correlation between SPI, ZSI and MCZI, and VCI, VHI, VDI, and VSWI in Maneh and Samolghan, Shirvan, Esfarayen, Garmeh, and Farouj stations, moderate correlations between the indices in Raz, Jirgalan, and Bojnourd stations, and no significant correlation between the indices in Jajrum station. As for the status of vegetation in North Khorasan province, it was found that the northern, eastern, northeastern, western, and northwestern parts of the province had favorable vegetation, while the province's southern, southeastern, and southwestern regions were covered with sparse vegetation. The results also showed that sparse vegetation played a major role in drought occurrence, with many of the severe and very severe droughts occurring in the southern part of the province according to the TCI index, while the north, west, northwest, east, and northeast regions of the province were in the favorable condition in terms of drought where most of the droughts were of the mild type. Furthermore, based on VCI and VHI, north, northwest, northeast, east, and west parts of North Khorasan province possessed the highest areas with mild drought, with the mild drought, persisted during the 19-year period throughout the province, where the highest area affected by the drought belonged to Shirvan, and Maneh and Samalqan cities in 2000 and 2013, respectively.However, most areas in the south, southeast, and southwest of the province were found to have experienced moderate drought during the study period. According to the VHI (used to displays the combined effects of vegetation and land temperature surfacewhen monitoring the drought), most areas of the North Khorasan province were found to be affected by moderate and mild droughts, with merely the southern regions of the province (Esfarayen and Jajarum counties) experiencing severe droughts. It was also revealed that Farooj, Shirvan, Bojnord, and Raz and Jorgelan were in favorable conditions in terms of drought, VSWI, and VDI. However, the south, southeast, and southwest parts of the province were covered by the most drought areas based on VSWI, and VDI throughout the study period, while normal and optimal conditions were mostly observed in the north, northwest, northeast, west, and east regions of the province.

It could generally be argued that applying various indicators can provide a better understanding of the drought situation, as each indicator examines the drought status based on a specific parameter (such as TCI and VCI) or a combination of several parameters (such as the VHI index). Moreover, evaluation of the correlation coefficients of indicators could be very effective in providing accurate results, considering the fact that some satellite-driven indicators such as the meteorological ones have a direct relationship with the drought status, whose accuracy can better be determined if their relationship with remote sensing indices is investigated. Therefore, considering this study's results regarding the Pearson correlation coefficients between meteorological and satellite drought indices, it is recommended that future relevant studies use VCI, VHI, VSWI, and VDI to monitor the status of drought.

Pediments are vitally important geomorphological units. Desert pavement feature is used for their classification. The characteristics of desert pavements are a function of geomorphological conditions and have unique properties in terms of different granulation parameters. A variety of methods are employed to determine granulation. The most common method is the sieving test, in which the particle size distribution curve is obtained using the cumulative weight of the grains passing through the sieve. Using image processing methods facilitates the identification, measurement, analysis, and spatial distribution of particles. The present study aims to prove that digital image processing is a viable alternative for traditional methods as the results from both procedures are similar.

Yazd-Ardakan plain is located in the range of 15 53 to 50-54 easts and in 31-15 to 45 45 north. In this study, ten points were randomly selected in 40 40 40 square plots in plain areas in Yazd-Ardakan plain basin. Sediment granulation was done by the mechanical sieving method. In order to granulate sediments, the samples were taken and transferred to the laboratory, and placed in a shaker to separate the particles according to their large diameter size by the sieves in the machine. After performing the calculations via Excel software, a graph related to the granulation of each point was achieved. WinArea-UT-11 can measure most physical coefficients of products such as perimeter, area, and the largest and smallest particle diameters. The parameters measured by the device were particles’ length and width.

In this section, the granulation results by mechanical sieving as well as the results obtained from the Win Area machine are presented. The following table, Table 1, is an example of calculating the weight percent and the percentage of cumulative frequency of particles in a mechanical sieve.Sizing by mechanical sieving was followed by placing the collected samples on the Win Area device, and photography was performed. The information obtained from the pebbles was saved in Excel software after shooting. A rectangular shape for each pebble is assumed. According to the length and width of the pebble device, the Pythagorean equation was used to calculate the particle diameter. Table (2): Weight and cumulative percentage of length, width and diameter of the machine using sieve diameter  Diameter (mm) Frequency percentage  Cumulative frequency percentage Frequency percentage of device length Percent cumulative frequency of length Frequency percentage of device width Percent cumulative frequency of widt Percentage of frequency of device diameter Percentage of cumulative frequency of device diameter According to the results obtained from the Pearson test in SPSS software, the correlation between the results of the cumulative frequency percentage of the parameters of length, width, and diameter of particles with the percentage of cumulative frequency calculated by the particles’ diameter in the mechanical sieve is above 70%. Additionally, the mean level particle content in all three parameters of particles’ length, width, and diameter is less than 0.05.

The results of the granulation diagram of each of the parameters of particles’ length, width, and diameter visually show that the graphs are almost correlated and coordinated with each other. Among these, the correlation between the mechanical sieve granulation diagram and the particles’ width is more consistent than the particles’ length and diameter granulation diagram. According to the grading results of each parameter in comparison with the mechanical sieving method, if a few number of grading diagrams of length, width, and diameter are shifted, the diagrams will completely match. Pearson test, obtained by importing the percentage of cumulative frequency of particles’ length, width, and diameter, shows that in samples 1, 2, 3, 4, and 5, which are related to the pediments, the grading diagram of a mechanical sieve is more similar to Particles’ width grading diagram. In samples with higher mean diameters, the similarities between the grading values of the mechanical sieve are approximately the same as the granulation of particles’ width and length.This study illustrates the similarity between the grading curve drawn from the mechanical sieving and the results obtained with the win area machine, and the drawn curves are visually matched with some shifts. Also, according to the results of comparing image processing methods with traditional methods, it is found that there is a significant correlation between the two methods, meaning that the results of digital image processing methods are similar to conventional methods. Therefore, the digital image processing method can perfectly replace the traditional methods.

Climate change conditions have been deteriorated in recent years due to increasing emissions of greenhouse gases, whose negative effects on human societies are one of the major concerns in 21st century, leading to introduction of several scenarios for predicting the climate parameters affected by increasing emissions of greenhouse gases. Therefore, this study sought to investigate the effects of climate change on prospective drought in Tehran province using the Standardized Precipitation and Evapotranspiration Index (SPEI). To this end, daily climate parameters (T-min, T-max, T-mean, and precipitation) of eight synoptic stations were predicted in for the study period (1996-2017), using GCM-based emission Scenarios (RCP2.6, RCP4.5, and RCP8.5) extracted from the IPCC's Fifth report until 2112. Then, the drought's SPEI was calculated based on the predicted parameters, followed by the evaluation of the spatiotemporal characteristics of the drought. A general review of the results showed that the most severe drought would occur in Abali station in July 2073, which would be almost unprecedented in its kind. Moreover, Tehran city would experience more drought stress than other parts of the Tehran province in the coming years. It should be noted that according to the analysis of future drought's time series, "Very dry" months in future would have a 4-month displacement to the backward and would be shifted from September to May than what had been recorded in terms of time period.

This study attempted to predict the precipitation and temperature data at the synoptic station level based on climate change scenarios using SDSM exponential microscopy technique. The section 2 of the article introduces the study area and the stations concerned, the climate change scenarios, the SDSM microscopy model, SPEI drought index, and regional zoning model. In Section 3, the regional drought will be calculated and spatially analyzed based on SPEI index using the predicted data. Finally, the last section of the study is devoted to the summary and general conclusions. Based on the monthly average observational charts and forecasts at each station based on each scenario, it can be claimed that the drought phenomenon is moving backwards in the coming years. In other words, most of the stations are predicted to experience their driest year from September to October. However, according to climate change scenarios, May, June, and July are symbols of high drought months in the coming years.

Temporal Analysis As one of the dimensions of drought characteristics, the detailed drought analysis offers very useful information regarding the intensity, duration, and frequency of drought. According to average monthly observation charts and forecasts prepared for each station in each scenario, it can be argued that the drought phenomenon is moving backwards in the coming years, according to which most stations are predicted to experience their driest years, especially in September and October of each year. However, the climate change scenarios revealed that May, June, and July would be the symbols of high-drought months in the years to come. Spatial analysis based on scenario 2.6 At first glance, it could be said that in all months of the year, the Tehran city would suffer water stress and drought crisis. On the other hand, according to the images obtained, the drought would have a moving trend from January to July, shifting from the west to the east of the province. However, the trend would be concentrated in the west of Tehran province from August to January, except for the December. Spatial analysis based on scenario 4.5 per month Scenario 4.5 reported more severe climate change than Scenario 2.6. The remarkable point in the obtained images was the frequent continuation of drought in the center of Tehran province, i.e., Tehran city. Spatial analysis based on Scenario 8.5 per month Scenario 8.5 shows more different changes in the distribution of drought-prone areas in the coming years than previous climate change scenarios. One of the points to consider in this regard is the significant reduction in the frequency of droughts in the west of Tehran province, which is even lower than those of the center and east parts of the province, being almost the opposite of what was found in the 2.6 scenario.

The comparison of data found for the observation years and the what was predicted for the upcoming years based on different scenarios shows that the frequency of droughts in the coming period. Therefore, if looked more closely, it could be found that the most severe and frequent droughts have occurred throughout the 7th decade of the 21st century, for which proper measures should be devised. The study's results also indicate that the probability of drought in the observation months will change more than what is anticipated, suggesting a seasonal retreat both in drought and wet season. Finally, according to the spatial analysis, it could be said that Tehran city will have higher temperature and precipitation stress (drought) than other parts of Tehran province. On the other hand, with the increase in altitude and the decrease in temperature, the severity of drought will decrease, whose effect on high altitude stations in this study was totally evident.