نشریه مهندسی اکوسیستم بیابان
پیاپی 35 (تابستان 1401)

As a complex phenomenon occurring due to a long period of poor precipitation, drought causes water scarcity in the soil and the hydrological system via hydrological, bringing about long-term consequences which may lead to severe economic, environmental, and social problems worldwide. Droughts are classified into four types: meteorological (rainfall), agricultural (soil’s moisture), hydrological (flow and groundwater), and socio-economic droughts. It should be noted that all types of droughts originate from meteorological ones, bringing about social and economic damages. on the other hand, Iran has long been known as a dry country with a low annual precipitation rate. Moreover, the development of spatial and satellite sciences, the application of remote sensing techniques, and GIS together with previous methods have led to more accurate results. Therefore, investigating the relationships between satellite-derived indicators and meteorological droughts could improve our understanding of the response of such indicators to climate change.

This study sought to investigate the relationship between remote sensing indices and the drought index (SPI). To this end, first, the daily precipitation statistics of 103 meteorological stations located in the study area were collected from the Iranian Meteorological Organization’s website for the 2000- 2019 period and their quality was controlled. Then, the SPI drought index was measured for all such data on monthly and annual scales using the McKay method, according to which the total annual precipitation was compared to the fit of different distributions. Then the probability of the observations’ experimental occurrence was calculated based on the relationship between the aforementioned equations. Moreover, after measuring the SPI index in the stations located in the study area, the MOD021KM outputs of the Terra sensor for the 2000-2019 period were obtained from the USGS website, to which necessary geometric, radiometric, and atmospheric corrections were applied. Finally, the NDVI, VCI, TCI, VHI, DDI, NDDI, EVI, NDWI, and SAVI indices were used to assess the drought conditions, and a monthly time series database was created for each of the indices over the past 20 years.

The study’s findings indicated the acceptable efficiency of remote sensing indices in extracting the data required for analyzing the drought in Central and South Zagros via the SPI index. The drought-related data and indicators of the study area were obtained and identified using the KMO and Bartlett index, whose range varies from zero to one. Accordingly, in cases where the index value is close to one, the collected data are suitable for factor analysis; otherwise, the results of factor analysis would be not appropriate for the intended data. In this regard, the results of Bartlett's statistics also suggested that the remote sensing indices affecting the drought in the study area were suitable for factor analysis, indicating that the confirmation of the opposite hypothesis, according to which there was a significant correlation between the variables.

This study sought to investigate nine remote sensing indices affecting the analysis of drought in Central and South Zagros. The results of factor analysis revealed that the drought in the study area was affected by three factors. In the first factor, SAVI, NDVI, VCI, and EVI indices showed the highest correlation. In the second factor, NDVI, DDI, TCI, and VHI were of great significance, and in the third factor, the NDDI index played the most important role. In the next phase, the relationship between the spatial pattern of remote sensing indices and drought’s spatial clusters was examined. Spatial relations analysis is a method to spatially analyze the randomness and non-randomness of the distribution of spatial variables. Furthermore, spatial autocorrelation is one of the most practical and important analytical tools for researching spatial relationships. In this regard, it was found that remote sensing indices and SPI drought index possessed a positive spatial autocorrelation in terms of spatial relationship in eastern, southern, and some parts of the central regions of the study area. Therefore, it could be argued that the areas were more affected by drought in terms of spatial autocorrelation index G *. On the other hand, out of the indices investigated in this study, SAVI and NDVI had the most similarity in terms of regions with positive cluster patterns, possessing the most positive spatial patterns. The results of the impact factor analysis performed on the correlation between the SPI and remote sensing coefficient confirmed that the spatial distribution of drought was of cluster type.

As a dreadful natural disaster caused by a severe reduction in precipitation rate, drought brings about, compared with other natural disasters, far-reaching spatial and temporal consequences, incurring severe damages. On the other hand, in late the 20th century, drought monitoring approaches underwent a paradigm shift, and advances in remote sensing and earth observation technologies allowed observations and monitoring of key drought-related variables over larger temporal and spatial scales than what the then conventional methods had already made possible. There are different remote sensing indices used to assess drought, including the PDI index which has been developed based on the spectral patterns of soil moisture changes in the NIR-Red space using the red and near-infrared bands of the ETM+ sensor. Therefore, as Khuzestan province is suffering from drought consequences, including but not limited to dust storms and economic difficulties, this study sought to identify the spatial and temporal trends of drought in the center of Khuzestan province.

The study area is located in southwestern Iran and the center of Khuzestan province at 31° 0ʹ 17ʺ to 31° 43ʹ 69ʺ N latitudes and 48° 35ʹ 51ʺ to 49° 32ʹ 2ʺ E longitudes covering an area of 7635/36 km2. To conduct the study, some twenty ETM+ remote sensing images of level-1 data taken from 1999 to 2018, (path/row 168/35) were collected from the United States Geological Survey website.After gathering the required data, some 411 random points were selected on the collected images, the pixel values of red and near-infrared bands were extracted and plotted against each other, and the slope of the best-fitted line, known as the soil line, was obtained. Then, the PDI drought index values were calculated using the slope and the values of the aforementioned bands. Finally, by applying a natural break classification method, different degrees were separated, and the drought’s trend of spatial and temporal changes was identified using Mann-Kendall's seasonal trend test at different significance levels.

The results of the spatial trend analysis of drought suggested that the trend was significant only in low drought and non-drought conditions. For the non-drought conditions, the probability of spatial changes was lower than the confidence level at 5% and 10% significant levels, indicating the significance of the conditions at these two levels, and thus, rejecting the null hypothesis at merely the 1% level. On the other hand, as the low drought conditions showed significant spatial changes only at the 10% significant level, the null hypothesis is rejected at the 1% and 5% levels. However, moderate and severe drought conditions revealed no trends in terms of spatial changes due to the higher probability values ​​of 0.28 and 0.3, respectively, which were higher than the determined significance levels. Moreover, the results of temporal trend analysis indicated no trend for the non-drought conditions, considering the fact that the null hypothesis was rejected at all significant levels. On the contrary, in the moderate drought conditions, a temporal trend was confirmed at all significant levels with the probability rate of 0.006 which was lower than all the assigned levels. Also, a temporal trend was found at low and severe drought conditions at 5% and 10% significance levels with a probability rate of 0.023 and 0.014.

The spatial analysis of the drought trend suggested that only the area with non-drought conditions had a significant increasing trend, which could be justified by the increase in the area of ​​irrigated land around water bodies in the area, especially around the Karun River in the west of the study area. The reduction in the area of land in the northeast of the study area with the low-drought conditions could be attributed to the rangeland degradation containing low and moderately dense vegetation.Moreover, the status of drought conditions in some sandy areas has changed from low in 1999 to moderate in 2018 due to vegetation destruction. The decreasing and increasing trends in areas of land with moderate and severe drought conditions, respectively, indicated the worsening of the drought conditions in the study area. Taking the changes in the drought index into account, it could be said that merely the areas with non-drought conditions remained unaffected by any significant increase or decrease in drought conditions, considering the fact that such areas are mainly wetlands, irrigated farms, and fish farms (that are naturally wet).However, the trend of the drought index value was found to be (highly) significant for other drought conditions, especially for moderate-drought conditions, indicating an increase in the severity of the drought conditions during the studied years. The frequent occurrence of dust storms in Khuzestan in recent years suggests that the results of this study correspond to the current reality of the region. In fact, it could be argued that during the last decade, the exacerbation of climate change and drought conditions on the one hand, and the development of construction projects and excessive extraction of water resources, on the other hand, have led to the dryness of many wetlands and wet areas, thus creating small deserts which are regarded as the main sources of dust storms in Khuzestan province within the past few years. Moreover, according to the findings of recent studies, desertification and drought trends have been increasing in recent years, indicating a great increase in the significance level of desertification in number 3 and 4 desertification centers in the east and southeast of Ahwaz, and a significant increase in the severity of drought conditions. This study proved the efficacy and applicability of the PDI drought index in drought monitoring.

in addition to pasture grazing, animals are fed on such sources as manual forage, farm straw, etc. Therefore, due to various socio-economic reasons, overgrazing and forage shortage exert adverse effects on rangelands, leading to their degradation. On the other hand, excessive exploitation of rangelands and changes in their use has led to the expansion of invasive species, altering the rangelands’ species composition and influencing the relevant ecosystem’s functions and services, which, consequently, ends in the destruction of ecosystems worldwide. In this regard, in cases where the invaluable and important species are overgrazed, the improvement of the rangelands containing perennial, high-yielding, and palatable species is recommended to restore the rangeland’s production capacity, reduce the competitiveness of invasive species, and increase the vegetation both quantitatively and qualitatively. Thus, it could be argued that identifying the factors involved in the germination and growth of invaluable species in rangeland ecosystems is required for the management, improvement, and restoration of rangelands.

This study sought to investigate the effect of irrigation interval, water salinity, and the soil’s clay content on the seed germination and the height of germinated seedling of Hedyasrum criniferum which is an endangered, palatable species indigenous to Iran’s rangelands, under greenhouse and natural habitat conditions. To this end, a factorial experiment was performed in terms of irrigation interval at three levels of 7, 10, and 14 days, water salinity at three levels of <1 (0.4), 2, and 4 dS m-1, and added clay contents at three levels of 0, 10, and 20% under greenhouse conditions with three replications, using a random sampling method. Moreover, the GLM method was applied to examine the factors affecting the herbal parameters of the Hedyasrum criniferum species.

The study’s results revealed that out of the three treatments mentioned above, only the irrigation interval had a significant effect on the H. criniferum species’ germinated seedling height and its germination percentage (α = 5%), with the greatest amount of germination (77.77%) and the highest germinated seedling’s height (4.93 cm) being observed in the seven-day irrigation interval based on the comparison of means. According to the species’ response curves, while the species’ height showed an ascending trend in proportionate to the precipitation rate, it had a reverse trend in proportionate to salinity. As for the clay content, it was found that the species’ height decreased up to 25% with an increase in the clay content. However, the trend was increasing for over 25% clay content.On the other hand, the analysis of the species’ response curve in terms of the amount of germination density indicated that while the number of germinated seeds increased with an increase in the precipitation rate, it decreased with an increase in salinity. Moreover, the number of germinated seeds responded to clay content the same as it reacted to the species’ height, getting decreased with up to a 25% increase in the clay content.

as found in this study, irrigation interval is a more important factor than the other two treatments. The tolerance level of germination and seedling growth was found to be at a 14-day irrigation interval, 4 dS m-1 salinity level, and 20% added clay content. Therefore, it could be argued that lowering the irrigation intervals may help the root growth. Furthermore, maintaining the moisture at 40-0 cm away from the soil profile can facilitate root growth and thereby increase photosynthesis. However, increasing the irrigation intervals may disrupt photosynthesis by creating a shortage in the soil’s moisture and decreasing the production of photosynthate materials to be transformed into the plant’s growing parts, checking the growth of the plant’s height. Considering the fact that Hedyasrum criniferum is regarded as a very high-quality forage in Iranian rangelands based on the rangeland classification indices in terms of forage quality, and that the species contains more protein and metabolic energy and higher nutritional value than alfalfa, and also its desirable ability to stabilize the soil’s nitrogen, the species can be used to convert the abandoned rain-fed lands in semi-arid areas to forage-planted lands and restore the destroyed rangelands in natural habitats. On the other hand, it was revealed that in natural habitats, the chances for the growth of the aforementioned species increased with an increase in precipitation rate, reaching its highest points in areas with average annual 650 mm precipitation. It should be noted that the precipitation range of the species’ habitats indicates the possibility of  H. criniferum growth in different climatic regions, including arid, semi-arid, and semi-humid regions. Therefore, it was found that the chances for the species' growth increased with an increase in precipitation rate from arid to semi-arid and finally, to semi-humid regions. Moreover, the study found that based on its optimal precipitation rate, the species prefers semi-humid climates.

Awareness of soil quality in agricultural lands and natural resources is essential to achieve maximum production and environmental sustainability. Although soil quality is not directly assessed, soil quality indicators are widely used today, including the physical indicators which are of great importance in measuring the soil quality, as they directly influence the plant growth and the soil’s chemical and biological properties. Therefore, it is necessary to evaluate the quality of the soil and to take its changes into account when using the land for the intended uses before its exploitation.  On the other hand, applying satellite imagery and GIS to extract the required information and map soil indicators to make optimal decisions has become an integral part of sustainable land management. Considering the changes in the soil's physical, chemical, and biological properties and the human-induced land degradation, it could be argued that the quality of the soil varies in different land uses. Therefore, the soil’s quality index can be measure in each unit through the land use map. In this regard, various studies have been conducted on land use-related soil index via remote sensing techniques, indicating that unscientific and uninformed changes in land use may have negative effects on the soil’s desired physical and chemical properties. Thus, this study sought to investigate the status of the soil’s texture and density in different land uses and assess its quantification using the Google Earth Engine system.

The Rudan basin is one of the sub-basins of the Minab watershed, whose rainfall distribution does not follow a uniform pattern, with roughly 242 mm average annual precipitation, more than 77% of which occurs during the rainy season (Autumn and Winter). On the other hand, the annual minimum, average, and maximum temperature rates of the study area during the study period (1980-2020) are 18.1 °C, 25.7 °C, and 33.02 °C, respectively, and the area’s average annual evaporation rate is 2858 mm. To conduct the study, the intended area was divided into five uses, including the moderate pastures, poor pastures, agricultural lands, garden lands, and canals. Then, a total of 218 samples were taken from all such land uses from the soil's zero to 10 cm surface, and some experiments were performed to determine the soli’s texture, sand percentage, and density using hydrometric and paraffin black methods. Open Land map was also used in Google Earth Engine. To this end, first the location of the study area was identified in the Google Earth Engine system. The data used in this phase included the Landsat series images related to the study period (January 1, 1950 to January 1, 2018) with a resolution of 250 meters. The location of the captured points was then determined using GPS in the Arc GIS 10.3 software. Moreover, variance coefficient analysis, overall accuracy, and kappa coefficient were used to evaluate and validate the obtained results.

According to the validation of the results obtained from the Google Earth Engine service, total accuracy was 95% and the kappa coefficient was 0.93. Furthermore, it was found that the amount of clay and silt decreased and the sand percentage increased with the change in land use over the large area of agricultural lands, which is consistent with the findings reported by Bewket and Stroosnijder (2003), Martinez et al. (2008), and Riahi et al., (2016) who found in their studies that the amount of clay and silt decreased and the sand percentage increased during the change of land use from forest to the agricultural and garden ones. Moreover, as suggested by Aghdami et al., 2019, Zare et al., 2011, and Wang et al., 2012, the soil’s physical properties, especially its texture, is one of the most important determinants in the distribution of plant communities in different land uses. Considering different land uses and agricultural activities in the study area and the fact that most of the area’s residents earn their living via farming, and based on the strategic document of Hormozgan province, the area is considered an agricultural territory (Hormozgan Management and Planning Organization, 2019) that has already experienced a variety of land-use changes. On the other hand, any change in land use may lead to the loss of natural resources and agricultural biodiversity (Rawat and Kumar, 2015; Seyum et al., 2019). Given the importance of agriculture in the region, any change in land use should be considered in the mid-term and long-term planning. Therefore, a detailed, up-to-date, inexpensive, and fast surveys are required to prepare development plans for various types of land uses, relying on the available data collected from the Google Earth satellite engine’s online image processing system. In fact, Landsat satellite images are processed in a fraction of minutes, which are then analyzed for evaluation and planning. This system is a safe and cost-free way to process large volumes of satellite images from various sources, accelerating the processing very well and saving a lot of time.

As the main source of water and life for humans and other creatures, rivers may sometimes bring about destruction and irreparable damage. Therefore, it is necessary to study the hydraulic properties of the flow and the riverbed’s area to set a safe zone for human activities around it. On the other hand, constructions built along the river’s route such as bridges, weirs, superstructures, etc. alter the river flow’s hydraulic behavior, which, in turn, could make changes in the riverbed. Thus, this study sought to examine the implementation of a hydraulic model of the Valian River and its results and to investigate the role of bridges (Chandar, Eskol Darreh, Ajin Dojin, and Velian) in the riverbeds' natural conditions. The study area for designating the river’s bed limit and riparian zone included the upstream of Eskol Darreh village, all the routes which pass along the Eskol Darreh, Velian, Ajin Dojin, Khorvin, and Chandar villages, and finally, the entrance of Kordan River at the downstream of Chandar village. The length of the main river is about 17.5 km, whose upstream coordinates located, according to the UTM coordinate system, at 485090 east and 3990600 north, and its downstream coordinates are located at 481050 east and 3977000 north.

To simulate the river under study, hydraulic parameters were taken into account, including the flood discharge with different return periods, Manning coefficient, the river’s geometry in the form of cross sections, and the data regarding the constructs built along the river’s route. Moreover, the flow’s hydraulic conditions were simulated and the necessary hydraulic analysis over the studied periods was performed using the HEC-RAS model. According to the applicable laws, the flood zone is designated under the river’s natural conditions in terms of 25-year flood discharge. In this study, the final riverbed’s limit was designated by identifying the hydraulic bed and considering the effect of morphological, legal, riverbed land use, and socio-economic studies. The riparian zone is normally located at a certain distance away from the riverbed, which was considered 4 meters for the Valian River. Also, the water surface profile was calculated for the constant flow mode according to the standard step-wise method using the Hec_Ras software. The calculations were performed based on solving one-dimensional energy equations (Bernoulli equation). The Manning equation was also used to calculate the energy loss in successive periods. Furthermore, other types of losses such as the periods’ expansion and contraction coefficients were taken into account, and the momentum equation when applied for periods when fast variable currents occurred (in mixed currents, including a combination of supercritical and subcritical currents, hydraulic jump, the current passing through the bridges’ underpasses and the junction of branches, etc.). In addition, this model can also analyze the effects of river-related constructs such as bridges, culverts, weirs, lateral weirs, and organizing constructs discussed in this study. Taking the possibility of developing a GIS model for the study area, By having and according to the width of the river bank mapping, some cross sections were prepared along the river from the main route and the flood plain, designated at certain distances away from each other based on the mapping of the river’s edges using topographic maps with appropriate accuracy (scale 1: 500) and GIS software, including the GeoRas and the ArcGIS software.

Zoning the floods in the Valian River with different return periods, this study compared the natural conditions of the river before and after the construction of bridges using a one-dimensional HEC-RAS model. The studied river was modeled in its current status under its natural conditions for floods with different return periods, including the 2, 2.33, 5, 10, 25, 50, 100, 200, 500, and 1000-year periods. The study’s results suggested that the constructed bridges had the greatest influence on the water’s cross-section flow and surface width, and the slightest effect on the water’s level and the balance of energy gradient. According to the results of the analysis performed on floods with a 25-year return period, it is recommended that due to its greatest amount of alterations at the cross-section current and the water’s surface width, Eskol Darrah's bridge be considered the highest priority in terms of management decisions and that the Valian bridge be the last priority in this regard.

When trying to designate the final riverbed’s limit for the Valian River in the study area, it was found that the trenching nature of the river’s bank, the alteration of the riverbed’s limit to facilitate the installation of rappers, the narrowed cross-section of the river, and the erosion potential had changed the river’s flood zone under its natural conditions. The results of water level analysis indicated that with an increase in return periods, the river’s flow rate and the flood level increased. Moreover, it was found that compared to natural conditions with a 25-year return period, the river’s longitudinal profile increased at its current status at the bridges due to the increase in the narrowness of the river’s cross-section. On the other hand, as the flow’s section has been narrowed at the bridges, eighter end of the bridges has been eroded and the water level has increased there. Moreover, the comparison of the natural and current conditions of the areas surrounding the bridges revealed that the Froude number has decreased with the changes made in the flow’s velocity and an increase in the water depth. Moreover, the presence of bridges in the flow’s route has led to an increase in free flow’s width and surface, and a decrease in the Froud number and the flow’s velocities in the 25-year return period. However, all of these parameters vary for the Valian bridge. Therefore, considering minor differences between the parameters in natural versus current conditions of the bridge, it appears that eighter the bridge has no influence on the flow’s characteristics or its modeling is erroneous. Taking the slight difference between parameters derived from modeling the bridge under natural and current conditions, the greatest and slightest effect of the bridge on the hydraulic parameters was found in the Eskol Darrah bridge and the Valian bridge, respectively. Furthermore, the highest amount of difference in the flow level was observed in the Eskol Darrah bridge (53.67), and lowest amount water level was found in the Valian bridge.

Emanating from non-whirlwind-based storms, gusty winds are regarded as the most destructive natural threats, causing extensive damage to infrastructure, agriculture sections, trees, power lines, and structures.120-day winds occur during the warm season of the year, typically starting from mid-May in eastern Iran and western Afghanistan and continuing until mid-September. Normally, the velocity of the winds varies sharply, sometimes greatly increasing the intensity of the gusty winds blows. However, the influence of the gusty of 120-day winds on the number of dusty days and the regions where the winds increase or decrease the creation of fine dust has remained unaddressed in the studies conducted on such winds. Therefore, in addition to examining the current status of the gusty winds, this study sought to investigate the role of the gusty winds (as an important element in 120-day winds) in creating dusty phenomena and days in the Zabul region, Iran, and Harat in Afghanistan using satellite images and statistical tests. In other words, this study attempted to answer the following questions:- What is the status of the gusty of 120-day winds in Herat and Zabul stations?- What is the relationship between the characteristics of the gusty of 120-day winds and the occurrence of dust phenomena in ​​Herat and Zabul stations?

This study used the data collected from Herat International Meteorological Station (with the international code OAHR awarded by the International Aviation Organization (ICAO)) located at 34 degrees and 13 minutes north latitude and 62 degrees and 13 degrees east longitude, and Zabol station in Iran. The METAR reports received from the databases of the University of Iowa in the USA and the Ogimet website concerning the Zabol International Meteorological Stations in Iran and Herat in Afghanistan (from 01/01/2012 to 12/26/2019) were decoded using the latest instructions, codes, and methods for Weather Monitoring, mentioned in Annex 3 of the Convention on International Civil Aviation, approved by the World Meteorological Organization. The reports provide some information regarding the area’s weather, including wind direction and velocity, wind direction, horizontal visibility, current weather, cloudy weather, air temperature, dew point temperature, past air pressure, and the weather status for aviation applications at the airport and non-airport stations.Having identified the period range of the occurrence of 120-day winds, the information concerning the gusty winds was extracted from the database. Then, to investigate the influence of the gusty winds on the occurrence of fine dust phenomena and evaluate the gusty winds’ intensity in each Zabul and Herat station individually, the station-extracted quantitative data of the parameter were classified, compared, and measured based on the intensity and quantity of the parameter’s frequency in both stations.

According to the study’s results, 8059 cases of gusty winds were reported to have occurred in Zabol station, whose velocity ranged from 9 to 32 meters per second. Within such a range, the highest frequency belonged to 17 meters per second with 1232 frequencies, and the lowest frequency belonged to 32 meters per second with merely one frequency.The frequency of the gusty winds’ direction in Zabol station was 8059 cases, the highest frequencies of which were found at 330 and 340 degrees with 5629 repetitions. The frequency of the winds’ direction in Zabul was exactly in line with the direction of the prevailing wind, i.e., the northwest. Moreover, the lowest frequencies of the gusty winds’ direction belonged to 120, 150, 170, and 190 degrees with merely one repetition.The frequency of the gusty winds was reported to be in 5700 cases in Herat station, whose velocity ranged from 5 to 32 meters per second, where the highest frequencies were reported as 13, 14, and 15 meters per second with 2342 repetitions, and the lowest frequencies were identified as 5 and 31 meters per second with merely one repetition. Moreover, 5700 cases were identified in Herat station in terms of gusty winds’ direction, whose highest frequencies were found in 10 to 30 degrees directions with 2685 repetitions, and the lowest frequencies belonged to zero and 120 degrees with three repetitions. On the other hand, the frequency of the winds’ direction in Herat was exactly consistent with the station’s prevailing wind direction, i.e., the northeast, just as the case was for Zabol station.Furthermore, a significant correlation was found between gusty of 120-day winds and the occurrence of dust phenomena in Herat and Zabol stations. To test this hypothesis, first, the frequency distribution of the gusty winds and the characteristics of soil phenomena throughout the period when the 120-day winds blew in the stations located in the study area were identified based on the results obtained from the mean test (which was also used for identifying the period when the winds blew). Then, a correlation test was applied to evaluate the association between the gusty of the winds and the dust phenomenon.

As one of the most important characteristics of wind, a gust may cause lots of damage to various infrastructures due to its strong fluctuations in a short moment. These strong blows can intensify the rise of dust in deserts and dry wetlands and expand the range of the dust phenomena to hundreds of kilometers away from the sources of the dust.It can be concluded that the difference in the frequency and intensity of the occurrence of dust phenomena cannot merely be attributed to the existence of a climatic feature such as wind and its gusts, and environmental and geomorphological factors are also involved in this regard. The environmental factor referred to is the dryness of the Hamon wetland and the desert nature of the north of Sistan and Baluchistan, preparing the ground for the occurrence or intensification of the dust phenomena by the wind’s blows.In Herat, the frequency of not-wind-induced soil erosion phenomena inside the station was 391.5% (almost four times) more than that of the wind-induced one. Therefore, it could be argued that due to the mountainous nature of the Herat region and the predominance of transitional soil phenomena, there is no source of dust production in the area. However, the dust transferred to the station from Northern Herat areas (that is, the areas within the range of 120-day wind activity with potential sources of dust production such as the southwest deserts of Turkmenistan) penetrates into Herat, referred to by the DU and HZ codes.

More than 40% of the global lands are covered by arid and semi-arid areas, a quarter of which is covered with dunes, On the hand, wind erosion contributes by approximately 60% to desertification. therefore, additives or stabilizers are used to control wind erosion and decrease its adverse consequences.Soil stabilization refers to process whereby a product is added to the soil to improve its properties. stabilizing agents are typically classified into traditional and non-traditional types. Hydrogel as a non- traditional stabilizer is a hydrophilic polymer with a three-dimensional network. In recent years, researchers have developed a series of polymers to be used for various purposes, including the enhancement of soil properties. In this regard, this study sought to investigate the applicability and effectiveness of co-acrylamide acrylic acid hydrogel and determine its optimal concentration as a stabilizer of sand surfaces. To achieve the optimal concentration, a completely random experiment design was performed in the SPSS environment with three repetitions for all three concentrations of 0.5, 1, and 2%.

Collected from the Siyazgeh desert in northern Isfahan province, Iran, the samples of sand dunes used in this study. To investigate the efficiency of the chemical additives used in this study on the sandy soil’s properties, the polymer was used at three levels (0.5, 1, and 2%) with 3 replications. Accordingly, metal trays with 100 × 30 × 2 cm dimensions were used to administer the wind erosion test and determine the threshold of friction velocity. Then, the control tray and the treatments were tested under different wind velocities (the comparison of the samples’ weight before and after the wind tunnel test showed a weight loss). Finally, the effect of polymers on anti-wind erosion ability was studied in terms of compressive strength, abrasion resistance, impact resistance, and crust diameter.

Determination of wind friction velocityThe effect of three different concentration solutions on the shear strength suggested that all three treatments were resistant to maximum wind velocity (15 m/s, duration time was 20 min) and they didn’t lose weight. On the other hand, the control treatment showed 5 m/s for the threshold of friction velocity.Treatments ResistanceThe results of variance analysis showed that there was a significant difference between the treatments (sig <0.05) and compressive strength in different concentrations, and that increased compared to the control sample. While treatment 3 had the highest resistance (1.61±0.18), no significant difference was found between treatments 1 and 2 (Figure 1).As shown in Figure 2, treatments 3 and 1 had the highest and lower resistance against the sanding (46.67±5.19 and 8.67±0.96), respectively.The samples treated with 2% polymer revealed the highest sheer resistance (5±0.56) (Figure 3). As shown in Figure 4, only treatment 3 was impact resistant.   As shown in Figure 5 most crust diameter revealed in the sample treated with 2% polymer (15.63±1.74).

Considering the results of this study, it could be argued that composite concentration plays a key role in the influence of polymer adsorption on the soil’s particles. on the other hand, it was found that the sand’s strength and stiffness increased with an increase in the concentration of the polymer solutions, which could be justified by an increase occurred in the interaction between sand particles and additive.

The mangrove ecosystem in the coastal desert and sedimentary islands northwest of Qeshm Island off the coast of the Persian Gulf is exposed to industrial pollution, urban effluents and oil pollution. Considering the fact that pollution can affect the ecosystems, any increase in the concentration of metals such as cadmium, lead, zinc, and copper may damage coastal ecosystems. On the other hand, the role of mangrove (as a coastal ecosystem) in accumulating heavy metals can be identified by measuring its transfer coefficient. However, as the heavy metal contamination in Qeshm mangrove ecosystem has still remained unknown, this study sought to identify and evaluate heavy metal pollution in the mangrove ecosystem of the Qeshm coast and to examine the ability of contaminants to accumulate in mangrove by calculating their transfer rate.

At First, ten mangrove stations were identified using Google Earth images. Next, mangrove sediments and leaf were sampled six times in 2019, which were then were encoded in plastic bags and transferred to the laboratory. Finally, the concentrations of heavy metals including zinc, lead, copper, and cadmium were measured using an atomic absorption spectrometer. Moreover, indicators such as CF, BCF, MAI, PLI, RI, and mPELq were used to assess the pollution of mangrove ecosystem in Qeshm.

According to study’s results, the heavy metals’ pattern was found to be Pb> Zn> Cu> Cd in the mangrove forest ecosystem’s sediments and leaves. Furthermore, the maximum and minimum concentration of zinc metal in mangrove’s sediments and leaves were found in stations 1 and 9, respectively. Moreover, while the maximum concentration of lead and cadmium belonged to the coastal station 1, their minimum values were found stations 8 and 5, respectively, both of which are located in the inland sediments of the mangrove ecosystem. Also, the maximum and minimum copper concentrations were identified in stations 2 and 10, respectively.On the other hand, the investigation of Qeshm mangrove ecosystem’ pollution revealed that while cadmium and zinc metals had moderate pollution coefficients, lead and copper metals possessed significant pollution coefficients. Moreover, the accumulation of heavy metals in mangroves were more than 1 in cadmium. However, the amount varied from 0.9 to 1 in zinc, lead, and copper. In general, it could be argued that mangroves can store and accumulate heavy metals in their organs. On the other hand, the MAI index is higher in coastal areas than in sedimentary islands. In fact, while heavy metals are highly accumulated in coastal areas’ mangroves, they are much less accumulated in sedimentary islands. Also, the PLI value is over 1in the whole mangrove ecosystem of the Qeshm island, indicating the island’s polluted state, whose maximum and minimum values belong to the coastal areas and sedimentary islands, respectively. Furthermore, the analysis of ecological risk (RI index) suggested moderate and low ecological risks in coastal areas and sedimentary islands of the Qeshm mangrove ecosystem, respectively. Also, examining the potential hazard level’s coefficient in the Qeshm Mangroveforest ecosystem (mPELq) showed that coastal areas and sedimentary islands had moderate and low pollution risks, respectively.

this study investigated the heavy metal contamination, its accumulation rate, and its transfer from sediments to mangrove leaves. Metal pollution with pollution indices has been studied that cadmium and zinc in the mangrove ecosystem in the coastal desert and sedimentary islands in moderate pollution and lead and copper in the pollution category are significant; However, the transfer rate from sediments to mangrove was high, indicating the ability of the plant to purge the coastal desert ecosystem from pollution. On the other hand, the Ecological and environmental risk indices and the environmental risk probability index suggested low and moderate pollution risks in the mangrove. Generally, it could be said that according to the pollution indicators, the Qeshm island’s mangrove-covered northwestern coastal desert contains higher concentrations of metals than the island’s sedimentary inlands. However, due to the coarser texture of the sediments, and the extensive distribution of coastal mangrove roots, the heavy metals’ transfer rate from sediments to plant organs is higher in these coastal areas than in sedimentary islands, considering the fact that soft sediments in sedimentary islands tend to absorb and accumulate heavy metals. Therefore, the coastal areas of the Qeshm island can be classified within the low pollution category. As mangrove forests possesses a high power transferring contamination from bed sediments to their leaves, they can be used as a new method for purifying the habitats of coastal desert areas, wetlands, and bays.

 Considered the habitat of a large number of living organisms, the soil is regarded as one of the most significant resources for fulfilling the essential needs of human beings, whose destruction brings about lots of damage to various aspects of the organisms’ life. As a natural phenomenon occurring in soils with sparse vegetation where the wind blows at high speed, wind erosion is a highly influential contributing factor to soil degradation, covering one-third of the world’s lands. On the other hand, wind erosion-induced detachment of the surface soil and the movement of quicksand causes enormous damage to various aspects of human life.  Meanwhile, arid and desert areas are more subject to the damage incurred by wind erosion and the influx of quicksand. Various methods have already been used to contain wind erosion and prevent its damage, including biological, mechanical, and soil fixation methods. However, in some areas where biological operations are difficult to perform, mulching is initially used to temporarily stabilize the region. In this regard, petroleum mulching has been the most commonly used method in Iran since 50 years ago.  Nonetheless, some experts believe that petroleum mulching increases soil temperature, raises heavy metals and hydrocarbons, intensifies groundwater and environmental pollution, decreases permeability, and inflicts harm on plants and animals. On the contrary, some other scholars argue that not only does petroleum mulching pollute the soil but also increases vegetation, animal population, and consequently the soil’s microbial population by raising the soil’s temperature and increasing its moisture. However, adding petroleum mulch to soil raises concerns about polluting the soil with petroleum materials and altering the soil’s physicochemical properties.

 This study used the soil samples collected in three replications from the 0-5 cm and 5-10 cm depths of both the control area and Hamidiyeh city’s sand dunes, Khuzestan province, that had been mulched for short-term (less than 5 years), medium-term (5-20 years), and long-term (more than 20 years) to investigate the physicochemical properties of the soil. The samples were then transferred to a laboratory where the soil’s physical properties, including the texture, true specific gravity, temperature, and humidity, and its chemical properties, including EC, pH, chlorine, carbonate, bicarbonate, calcium, magnesium, lime, phosphorus, sodium, potassium, and the sodium adsorption ratio were examined and analyzed using the SAS software.

 The results revealed that while petroleum mulching caused significant changes in the soil’s temperature, moisture, chlorine, bicarbonate, potassium, EC, and pH, it exerted no influence on the soil’s texture, calcium, lime, and sodium absorption ratio. It was also found that due to its black color, petroleum mulch absorbs sunlight and increases the soil’s surface temperature, decreasing the soil’s permeability and moisture with its greasy hydrophobic nature. Moreover, the study found that compared to the control area, petroleum mulching increased the amounts of the soil’s EC, bicarbonate, phosphorus, and potassium, and reduced its magnesium, chlorine, true specific gravity, and sodium in some areas. Taking the above-mentioned results into consideration, it could generally be argued that in addition to influencing the soil’s physicochemical properties, petroleum mulching makes significant changes in the moisture, temperature, true specific gravity, pH, EC, bicarbonate, chlorine, potassium, and phosphorus of the soil. Furthermore, the investigation of the effects of petroleum mulching in the region suggested that most of the restrictive changes made in the region occurred during the short term, with the changes turned towards the improvement of the soil’s quality and fertility and the increase in the soil’s temperature by the establishment, improvement, and growth of vegetation over time. Therefore, if mulching does not helps improve vegetation due to the special conditions of the region (for instance, non-exclosure of the region and preserving it throughout the first mulching years), petroleum mulching is not recommended as it increases the temperature, decrease the moisture, and restricts some properties of the soil in the short-term. However, should there be any chances for the improvement of vegetation, petroleum mulching will increase the soil’s quality.

 Considering the rapid changes occurring in natural phenomena of the earth and their considerable influence on human life throughout time, it is crucially important to thoroughly examine such changes so that one can better understand the natural and human processes involved in those changes. Monitoring and assessing the areas where the aforementioned changes occur are considered as important steps in national development and the management of natural resources. In this regard, remote sensing technology is uniquely applicable in collecting information concerning such phenomena, taking into account various advantages of multispectral satellite imagery, including their availability and interpretability. This study, therefore, sought to investigate the changes made in Arjan wetland using RS and GIS technology. To put it more precisely, the current study examined the changes that occurred in the wetland’s banks, the decline of the area covered by the wetland’s water, and the changes made in the earth’s surface temperature and groundwater level. Throughout the past few decades, remote sensing technology has widely been used by scholars to detect such changes over time. On the other hand, coastal areas, especially inland lakes, have received special attention as ecological environments.

 This study used two types of data: meteorological data including precipitation, temperature (average, maximum, minimum), humidity, evaporation, and transpiration data, and remote sensing data, including the information collected from Landsat and MODIS images to calculate water indices and surface temperature. It should be noted that MODIS satellite images used in this study possessed low spatial resolution and high temporal resolution. Moreover, the NDWI was calculated for the study period (1968-2018) using coding in the google engine system. On the other hand, grace satellite imagery was used to estimate the alterations made in the groundwater level within the study area. Moreover, the data regarding the observed wells within the study area were used to validate the results and zone the aquifer’s water level. To determine the optimal position of the earth's surface and remove hydrological effects, the GRACE satellite (GLDAS model) was used.

 Like other lakes, the Fars province’s lakes are completely dependent on the status of water resources in the related watershed. Having been dried up since 2013, Arjan seasonal wetland, where the water height reaches one meter during high water periods, is currently in critical condition. In winter and spring, the surplus water is stored in the surrounding plain due to the increase in the plain’s surface inflows and the limited irrigation capacity in its eastern part, turning the wetland into a lake. In this study, first, the area of ​​Arjan wetland was examined in terms of climatic parameters. While Arjan Wetland experienced lots of fluctuations throughout the study period (1986-2018), it could be argued that its main crisis started in 2010 when the area of ​​the lake was reduced to less than half, and finally became zero in 2013.According to the obtained results, the wetland had its largest area in 1989 (14.78 square kilometers) when, based on data recorded at the meteorological station, the precipitation rate was 488 mm, which is regarded as one of the maximum precipitation rates throughout the study period. On the other hand, the time series data collected from the GRACE satellite and validated via Piezometric well’s data were used to examine the status of groundwater in the Arjan aquifer during the study period (1986-2018). The time period considered for the investigation of the changes that occurred in the aquifer was from 2003 to 2017. According to the data extracted from the GRACE satellite, the highest amount of groundwater decline occurred in 2018 by 20 cm. Also, the analysis of the general trend of changes shows that the decline rate is more than 8 cm per year.

 The consequences of climate change may be exacerbated in different regions by human activities-induced changes in the climate and the drying up of inland continental lakes. As a climatic hazard, the drying up of lakes is a critical issue to be taken into account, the consequences of which, as shown in this study, will affect the climatic conditions of the region and even the surrounding areas. Arjan wetland is an Iranian seasonal lake with fresh water whose area has been declining in recent years due to climate change and reduced precipitation rate, getting totally dried up recently. As found in this study, the wetland has completely been dried up as a result of a significant decline in its area from 1986 to 2018. It was also found that the Arjan aquifer’s groundwater level has decreased by roughly 20 cm.