نشریه مهندسی اکوسیستم بیابان
پیاپی 26 (بهار 1399)

Plant species as the primary producers of ecosystems and important structural components play a major role in the ecosystems sustainability as well as feeding domestic and wildlife livestock. Determining the preference value of plant species is essential to maintain plant health and the balance of livestock in rangelands. Various plant species with different growth and phonological characteristics have different grazing values in rangelands. In addition to plant characteristics, preference value of plant species could also be affected by livestock and regional conditions. Sheep and goat livestock are physiologically different, displaying different behaviors as a result. While many studies in this field have been carried out on the preference value of species in summer rangeland, few researches have so far taken the winter rangelands into consideration. Therefore, this study set out to investigate the preference value of plant species in winter rangelands for sheep and goats in Jiroft city.

The study region is located in winter rangeland of the Baqer-Abad which is 10 kms off the Jiroft city. The Preference value of the plant species was assessed in autumn and winter for different age classes (one-year old ewe, three-year old ewe, and five-year old ewe) of sheep and goats, using filming method. For each age class, three livestock were selected and their grazing time was measured individually within an hour. Then the relative grazing time of the animal was calculated for each plant species. Two-way ANOVA and LSD test were applied to examine the effect of livestock type and age on the preference value of the species. One-way ANOVA was also used to investigate the effect of seasonal grazing on the preference value of species.

The results of the study indicated that the preference values of the plant species differed for sheep and goat animals. To be specific, 64% of the species were the same for sheep and goats in terms of palatability, and 36% of the species were different in this regard. Moreover, it was shown that annual plants and Jaubertia aucheri species had the highest preference value for sheep and goats respectively, and that the Ochradenus ochradeni had a very low preference value for sheep and goats, making them show a slight tendency to consume it during the grazing season. However, as found by the study, the abundance of thorns in Lycium shawii, Acantholimon scorpius and Cornulaca monacantha led to their considerable preference value reduction in such a way that the sheep did not consume Lycium shawii and Acantholimon scorpius. Furthermore, the findings suggested that Cornulaca monacantha had a lower preference value for goats and sheep, and that Rhazya stricta, as a poisonous plant, was not found in the sheep's diet, and the goats had little desire to graze it. According to the results, the type of livestock had no significant effect on the preference value of Hammada salicornica which was somehow palatable for both sheep and goat. On the other hand, although Ziziphus spina-christi was not grazed by sheep, it had a high preference value for goats. In this regard, the three and five-year old goats spent more time on grazing Ziziphus spina-christi compared to one year-old goats. It was also found that Preference value of plant species significantly changed during the grazing season except for Jaubertia aucheri and Ochradenus ochradeni.

The daily diet of sheep and goat in the winter rangeland in Jiroft was mainly comprised of Annual plants. Producing annual vegetation is highly dependent on climatic conditions, especially rainfall which is sharply reduced in October and November. Therefore, young livestock which are not capable enough to graze shrubs need supplemental diets in October and November. The Jaubertia aucheri, which is of high preference value for sheep and goats, has little fluctuations throughout the grazing season, playing a very important role in sustainable production of annual plants in the region. Moreover, as overgrazing may endanger this plant species due to the shortage of one-year-old plants, it should be taken into account in conservation management plans, especially in the beginning of grazing season.

As a serious threat for human societies, especially in arid and semi-arid regions, dust storm is an irreversibly destructive phenomenon with irreparable effects. Being caused by dust storms and the movement of fine soil particles, desertification and wind erosion are two important environmental crises in arid and semi-arid areas which may bring about some social and economic consequences including an increase in migration of people, especially the elites, unemployment, sharp reduction of revenues in various urban and rural jobs, decrease of crops production, tourism downturn, disruption of air transportation, closure of training and recreation centers etc. In this regard, considering the detrimental effects incurred by dust storms on the health and economy of a society and the climate change, it should be noted that understanding the nature, origin and effects of dust storms could play an important role in identifying and setting its control methods. This study, therefore, sought to investigate the causal relationships between the influential factors on dust storms as identified by the DPSIR model, weighing the identified criteria and indices by the experts via the AHP technique, and ranking the specified strategies by TOPSIS in Rigan city, Kerman province.

Based on the review of the related literature and the data collected form field observations, the cyclic causes of wind erosion were examined, using the DPSIR framework. The criteria and indices identified by administering a standard questionnaire were confirmed by experts (selected from those working in departments of Environment, Natural Resources, Agricultural-Jahad, Environmental Health, Urban Planning, and some University lecturers and faculty members). Validity and reliability of the data were measured by SPSS software. The criteria selected for analyzing the data are the same as the four main elements of the DPSIR model: the driving force, pressure, state, and effect, each containing a number of indices which are as follows: the driving force indices include the population growth, inward immigration, land use, natural resources management, increase in water demand, public awareness and, urban development; the pressure indices are health, security, immigration, employment status, income status, investment, agriculture, and the environment; the state indices comprise of the land use change,  environmental degradation, utilization of water resources, rising diseases, inward immigration, social welfare decline, destruction of agricultural products, soil degradation, and air pollution; the effect indices include Destruction of cities beauty, immigration from villages, rise of respiratory diseases, destruction of natural resources, expert migration, landform change, increase of Particulates, drought, and the downfall of agricultural productivity. The criteria and indices were then weighted by AHP method through Expert Choice Software and finally, the proposed strategies were ranked according to TOPSIS method.

Having applied DPSIR model, the cycles of the influential factors on dust storms were examined, followed by the weighing of the identified criteria, and the indices confirmed by the experts, using AHP technique through the Expert Choice software. The results of the study indicated that the driving force with the weight of 0.379 was, from among the four criteria, ranked first, followed in turn by pressure with the weight of 0.257, the state with the weight of 186, and the effects with weight 160/0. On the other hand, the findings showed that out of the final indices weights, Population growth with the weight of 0.75 ranked the first, and increase of water demand, and the environment were ranked second and third with weights of 0.67 and 0.059 respectively. Finally, the TOPSIS method was used to rank the responses whose results were turned out to be as follows: 1-Proper management of water resources (592/0); 2- Preventing dam construction (5/175); 3-Pebble mulch (0, 75%); 4. Not applying inefficient models, especially in agriculture (519/0); 5. Enforcing existing laws regarding environmental protection (494/0); 6- conducting seedling operations (427/0); 7- Increasing public awareness (0.415); 8. Mulching (0.440) 9. Constructing sediment trap (0.339); 10. Using Biological wind-break systems (0.346).

As a potential threat to human survival, dust phenomenon is considered as one of the most important environmental crises in arid and semi-arid regions. Kerman province includes more than 17.6 percent of the Iran’s desert lands, the most significant part of which are located in its eastern regions including Rigan, Fahraj, Norshshir, and Bam that comprise of 1302,000 hectares desert lands, accounting for more than 55 percent of the province's total desert areas. Due to such causes as frequent droughts, seasonal drying of rivers, lack of suitable vegetation, and high evaporation, Reagan city experiences a large number of dust storms annually. In present study, DPSIR model was found to be effective in identifying, from among the various factors suggested by the experts, the most important factors affecting local dust. It is consistent with the results found by Khatibi et al (2015) who emphasized the necessity of using this model in solving environmental problems. In the same vein, Salehi and Zebbardast (2016), with the cooperation of the Tehran environmental organization, identified and categorized the factors affecting air pollution in Tehran city in the current state of affair, using the causative-effect chain model (DPSIR). The findings of the current study showed that the driving force with the weight of 0.397 had the highest weight, followed by the pressure (0.275), state (0.186), and effects (0.160) respectively. In fact, it was found that accurate identification of the driving forces in each region could be a great help in solving their problems which is consistent with the results found by Jafarzadeh Haghighi Fard et al. (2013). As for the final weighting, the findings suggested that population growth with a weight of 0.5 was the most important index, a fact that corresponds with the findings reported by Shahi et al. (2018) and Nemati and Sardari Leather (2017). The results of this study also indicated that the proper management of water resources in different areas and the utilization of nature elements were of high importance.

As a manifestation of land degradation, desertification is regarded as one of the natural hazards that is spreading rapidly due to human interference in and misuse of nature. There are many challenges caused by this phenomenon in most regions of Iran throughout recent years including the loss of fertile lands, reduction of forest populations, biomass of rangeland and fertile plain, decrease of aquifer water level, decline of water quality, poverty, and migration.

North Khorasan Province with an area of 28182 square kilometers is located in northeast of Iran. A considerable part of the province has been suffering from reduced tolerance due to significant land use changes, vegetation degradation, and deforestation. The region is highly vulnerable to desertification because of environmental pressure and extreme equilibrium changes. However, few studies have been conducted so far on desertification mapping and the identification of its main factors in the province. This study, therefore, sought to identify the main destruction criteria in the province, providing a map and assessing the hazards of desertification through the two Iranian MICD and IMDPA models. To end this, the required data including aerial photos, topographic maps, etc. were collected at the first stage. Having converted the collected data to appropriate formats, the initial maps of slope, aspect, DEM, land use, and land units were extracted. As for the assessment of desertification hazards, IMDPA and MICD models were applied, in each of which the desertification criteria were identified and scored. Moreover, the severity of desertification of each land unit and that of the whole area were determined by the two models. Finally, the present desertification map of the area was obtained through the abovementioned methods.

According to the intensity map of desertification hazard extracted from the IMDPA model, the average numerical value of desertification intensity in North Khorasan province was reported as being 2.67, indicating the moderate to severe desertification hazard class in most parts of the province. Based on the model, effective criteria in desertification included climate (3.2), erosion (2.76), agriculture (2.9), geology (2.2) vegetation (2.8) and soil (2.3) respectively. The results of the study showed that based on the MICD model, 80 percent of the province's regions faced with moderate to severe desertification hazards.

Northern Khorasan province includes several species affected by special environmental conditions and two vegetation regions of Iran i.e. Turonian and Hirkani. Land Use Intensive changes and vegetation destruction precipitate the desertification in this region. It results in increasing the risk of flood, decreasing groundwater levels, salinization, poverty and migration of inhabitants. As found by the study, desertification criteria were classified in the following order: climate (3.2), agriculture (2.9), vegetation (2.8), erosion (2.76), soil (2.3) and geology (2/2). Therefore, the climatic factor with the value of 3.2, low rainfall, and potential evapotranspiration indicators (more than 70%) could be regarded as the main factor in increasing the desertification intensity of the region. Moreover, it was found that the destruction of agriculture and vegetation which represents direct human intervention in the environment and resources, was, after the climate, the second highest influential factor on the severity of the desertification of the region, accounting for the excessive exploitation especially in rangelands (in the form of excessive gravel and picking plants). The ecosystems, being subject to overgrazing, constant land use changes, exploitation, and degradation are, according to results derived from the application of both two major models mentioned on vulnerable ecosystems in the province, located in the rangeland landscape. Thus, in addition to being highly vulnerable, they reduce the production of forage and medicinal plants and turn into desert lands.Land use changes in forest ecosystems and their transformation into agricultural lands have played a significant role in changing the face of these ecosystems in recent years. These changes have increased flood conditions at different levels, risking the inhabitants of the area being flooded after every rainfall. Considering the inherent potential of desert ecosystems, high erosion which reflects the low soil capacity against erosion could accelerates salinity, drought and, consequently, degradation of vegetation. Maintaining balance of livestock and pasture, administering some other methods for exploiting the pasture including planting medicinal herbs, beekeeping, ecotourism development, floodwater spreading (which maintains the economic conditions of local communities and preserves vegetation) and controlling flood are regarded as the managerial priorities in the province. Considering the importance of the multi-dimensional phenomenon of desertification in the region, it is, therefore, suggested that preparing the strategic plan for risk management of desertification of the province and introducing appropriate, conservative, aggressive and competitive strategies for various conditions could be an important step forward toward improving the vegetation of rangelands, increasing forage production, controlling water and soil erosion, controlling water and soil, controlling flood and damages, feeding and strengthening  groundwater resources, improving environmental conditions of the areas, and managing the drought consequences.

Groundwater is considered as one of the main resources for drinking water, agriculture and industry. While groundwater is taken as a reserve resource in some areas, in other areas it may be used for supplying potable water due to their easy availability. Moreover, groundwater analysis is an essential factor in maintaining its access. In fact, modeling and predicting the groundwater level play a significant role in preserving the environment, maintaining the balance of the groundwater system, controlling changes in groundwater levels and preventing the escalation of land subsidence. On the other hand, climate change and the decline in groundwater table have been proved to be one of the main causes of land degradation in the past decades. According to Iranian Ministry of Energy, about 7 billion cubic meters of groundwater reservoirs are declining annually. Also, from among 609 plains in Iran, approximately 350 of them are known as the forbidden ones. The increasing number of prohibited plains from 15 wells in 1968 to 199 ones in 2001, and rising the dried plains into 350 ones in 2015 indicate the inappropriate status of water resources in Iran. Meanwhile, the highest amount of water scarcity in underground reservoirs belongs to the second grade Salt Lake as well as the Kerman Plain which has attracted more attentions in recent years as one of the most important plains of this area due to the large decline in its groundwater.

This study set out to model the flow of groundwater in the Kerman plain aquifer under the influence of climate change for the upcoming period, using the GMS model. To this end, HADCM3 model, LARS model and A1B, B1 and A2 scenarios were applied for the investigation of the effects of climate change on aquifer volume and groundwater declines. Finally, having applied four different scenarios, the performance of each management options and the effects of different climate scenarios on the decline of the aquifer were examined.The results of the exponential microscopy indicated a minimum increase in the temperature between 0.59 to 0.86 degrees Celsius and a maximum temperature increase of between 0.56 to 0.85 degrees Celsius. The reported increase in minimum and maximum temperature in the upcoming period is consistent with the results of the studies carried out by Zhang and Nyinger (2005), Mosheh Boani and Merid (2006), Khorshid Doost and Ghavidel Rahimi (2006), Kukchi et al (2006), Yano et al. (2007), and Babayan et al. (2009), where temperature increases have been predicted.Comparison of long-term annual precipitations suggested prospective increase in the rainfall which is consistent with the results of the study conducted by Steel Dani et al. (2008). Moreover, according to the findings of the current study, the lowest amount of precipitation in scenario B1 would occur from 2011 to 2030, which is 10.22 mm more than the base period rainfall. This is while the highest rainfall was expected to occur with a rise of 80/15 mm within the time period of 2011-2030 in scenario A2. As found by the simulation of the groundwater model (GMS), there was an acceptable accuracy for simulating the aquifer of Kerman Plain. In terms of Kerman aquifer quantity, the results suggested, after a steady-state calibration, that RMSE, MAE and ME values were 0.38 m, 0.21 m, and 0.20 m, respectively, showing acceptable accuracy of modeling in the mode was lasting. Having set the proper performance of GMS model, four different scenarios were used to simulate the effect of climate change on the station's level, and its changes were compared with the base period. On the other hand, the decline in water level would be 10.6 -10 in the first scenario. The levels of water decline within climate change scenarios A2, A1B and B1 for were 11.9, 12.36 and 16.22 for the second scenario, 16.41, 16.66 and 17.30 for the third scenario, and 16.65, 16.9 and 18.15 meters for the fourth scenario respectively.

Although climate change directly affects surface water resources changes in major long-term variables such as rainfall, temperature, evapotranspiration and transpiration, it is difficult to determine the relationship between climate change variables and underground water. This study, therefore, attempted to predict the relationship between climate and groundwater levels for the upcoming period. Comparison of long-term annual precipitation indicate in increase in precipitation which is consistent with the results found by Steel Dani et al. (2008). According to the findings of the current study, the calibrated model has acceptable accuracy and the mathematical model can simulate the normal conditions governing the aquifer of Kerman Plain. Having obtained the proper performance of GMS model, four different scenarios were used to simulate the effect of climate change on the station's level, and its changes were compared with the base period. The results showed that an 18-meter water decline would not be expected in such a situation.

water is necessary for human, animal and vegetation lives. Therefore, providing sufficient water is an undeniable necessity for sustaining creatures’ lives. Development of water supplies, thus, should occur in such a way as to keep the hydrological balance and biological functions of all ecosystems which is crucial for marginal lands. Precipitation storage is the general name for all different techniques used for collecting runoff and rain water to be saved in the soil profile or tanks and be used for growing trees and crops and developing them in dry lands. The precipitation storage is applied for afforestation in arid and semi-arid regions whose rainfall rates are not enough to sustain a good seedling or tree growth. Precipitation storage can increase the rate of planting trees in drought regions through the collection of rainfall, and runoff enhancement. Therefore, these techniques could compensate for the lack of soil moisture and help overcome good spells in critical growing stages, securing good water for plant when rainfall is erratic. This study, therefore, sought to investigate the effect of different precipitation storage techniques on preserving soil moisture and some growth characteristics of Acacia oerfota (Forssk.) Schweinf seedlings in Paired watershed of Dehgin, Hormozgan province.

Paired watershed of Dehgin is one of the sub watersheds of Esteghlal dam in Minab, Hormozgan province. Having collected Acacia oerfota seeds in the summer of 2018, they were planted in plastic pots. Collar diameter, stem height and quality characteristics of seedlings were measured. Seedlings were then planted with three replications (three blocks) in four treatments (diamond-shape micro catchment, semi-circular bunds, pitting, and control). following four months and five rainfall events, growth and quality characteristics of seedlings were measured in different precipitation storage techniques and the collected data were analyzed, using two-way analyses at the level of 95%. Soil moisture was measured based on different precipitation storage techniques and control, and the extracted data were analyzed by two-way analyses. The relationship between soil moisture, collar diameter and stem height were also measured via Pearson's correlations.

the results of the study indicated that the seedling vitality with the amount of 2.86 was significantly lower in control than it was in different precipitation storage techniques. Collar diameter of seedlings in semi-circular bunds (1.95 mm) was higher than what it was in diamond-shape micro catchment, pitting and control (0.92, 0.88 and 0.89 mm). Height growth in semi-circular bunds with the amount of 10.12 cm was significantly higher than that in control with the amount of 6.2 cm. These significant differences were due to the function of different precipitation storage techniques. Soil moisture percentage in all treatments was reported as being different (p<0.05). The amounts of soil moisture were 13.46%, 11.95%, 11.5% and 10.34% in diamond-shape micro catchment, semi-circular bunds, pitting, and control respectively. It was also found that soil moisture had positive direct effect on collar diameter and seedling height (p<0.01).

Vitality and establishment of tree seedlings depend on soil conditions and available moisture. As rain water is free of salts and other minerals that may harm plants and prevent their growth, it deemed great for plant growth. Considering the fact that rain water percolates into the soil, it forces salt down and away from root zone, allowing roots to grow better and making them tolerate more severe drought. The construction of diamond-shape micro catchments, semi-circular bunds and pitting in the study region, and collection of rain water and runoff led to the increase in soil moisture by improving infiltration rate, and thus facilitated plant growth. On the other hand, as plants require large quantities of water for growth, water was used during photosynthesis to produce carbohydrate as a necessary element for plant growth. Moreover, it is evident that leaves are important organs for photosynthesis and play an important role in survival and growth of plants. As the findings of the current study showed, soil moisture was higher in control method. It could thus be concluded that lower growth in control is due to lower moisture.The results of this study indicated that precipitation storage techniques were highly crucial for the soil moisture storage to improve vegetation in arid and semi-arid areas and increase their growth and vitality. It was also found that soil moisture content and also growth characteristics of drought-tolerant seedlings of Acacia oerfota, were higher in semi-circular bunds than those in control and other precipitation storage methods. These seedlings have suitable shoots and large green leaves without dieback in dry climate of Dehgin, resulted from the rain water and runoff collected through precipitation storage techniques and absorbed by plants. Moreover, among all treatments, semi-circular bunds were the best precipitation storage methods for afforestation and pasture improvement in the studied region.

Wind erosion is one of the important aspects of land degradation in arid and semi-arid areas. Countries located in arid and semiarid belt of the world including Iran have always been faced with this phenomenon. Wind erosion assessment models use different scores to determine the erosion rate in a given class. However, due to the spatial and temporal complexities and the multiplicity of factors affecting the ecological conditions of the region, it is impossible to fully rely on such results and use them for targeting and prioritizing the areas and providing suitable solutions for their management. Nevertheless, Bayesian Belief Networks (BBN) are based on probabilistic approaches which display the uncertainty in the evaluation of phenomena in terms of probability. These Networks are essentially developed as tools for analyzing decision-making strategies under uncertainty. Accordingly, this study set out to estimate the potential of the BBN as a relatively new and probable means for estimating the wind erosion and, finally, to evaluate the management scenarios for controlling wind erosion in Isfahan province.

To start the process of modeling the Bayesian Beliefs networks with regard to the purpose of the study, suitable variables were selected for modeling the BBN by reviewing the related literature and asking the experts opinions. In the next step, the relationships between the variables were determined, using the impact graph. The impact diagram shows the relationships and effects of the variables on each other and on the output node of the model (the amount of wind erosion). Finally, in order to create a model and formulate the conditional probability tables of model variables, the impact diagram was transformed into a BBN model, using the Netica software. The Bayesian Belief Network Model was validated by sensitivity analysis, the results of the analyses carried out by experts, and the comparison of the obtained map of Bayesian model with the wind erosion map in Isfahan province. The ROC curve characterizes the relative performance of each model. The area under this curve is called the AUC and the model with the highest AUC has the highest relative Function. The AUC equals 0.5 equivalent to the neutral model and the closer this value is to 1, the higher the Function of the model would be.

Having applied the final model of Bayesian’s belief network, the causal relationships between the variables affecting the rate of wind erosion were shown. The target variable in this model was wind erosion. As the findings of the study indicated, geological variables, land management, topography of the area, soil texture, rainfall and frequency of erosive winds were considered as key variables of the model. In order to run the model, information about each of the key variables was taken from the area at the province and fed into the model. Finally, the model was designed to estimate the amount of wind erosion in each sampling point. Based on the output of the model, the probability of wind erosion in each unit was used to zone the probability of wind erosion in the study area. The overall sensitivity analysis of the model also indicated that the wind erosion rate of the area had the most sensitivity to the wind velocity and speed, the frequency of erosive winds, and the protection of the earth's surface. On the other hand, the least sensitivity was reported for such variables as soil texture, geology and topography. Moreover, a high correlation between the results of the two models was found. According to the results of the ROC curve, the area under the AUC curve for Bayesian network model is 0.79, suggesting acceptable model accuracy.

It was shown that the BBN presented the probability of different wind erosion rates for each sampling point in the study area. In BBN, the results are expressed in the probability language and managers are to choose and implement timely and appropriate management decisions to reduce the risk of wind erosion in the region. The designed model in this study could be implemented in all regions. However, depending on the conditions of each region, the number of variables in the model may be increased or reduced. The study used Bayesian belief networks in the critical areas of wind erosion in Isfahan province. This model well demonstrates the importance of implementing wind erosion control projects to assist in sustainable land development to prevent migration, foster agricultural conservation, increase industry development and bio-resources in desert areas with desertification control.

Lack of rainfall and the subsequent drought could lead to changes in rangeland ecosystems. Monitoring rangelands to distinguish climate change from management is considered as one of the favorite research areas among range experts. Several studies have so far conducted on the effects of drought on vegetation in rangelands whose results indicate that vegetation and species density are strongly affected by drought. For instance, Zhang et al (2016) investigated the drought events in China over the period 1982–2012 and examined the impacts of droughts on vegetation productivity. The findings of his study showed that vegetation productivity was significantly influenced by droughts, and that the effects of drought on vegetation productivity varied with vegetation type. It was also found that from among major vegetation types, grasslands displayed the greatest sensitivity to droughts. However, the impact of climate change on biodiversity indicators has been underresearched. In fact, the problem of biodiversity response to changing microhabitat conditions has not been fully elucidated (Jastrzębska et al, 2009). Therefore, Ammodendron persicum reserve was selected for an investigation of trend change of soil physical and chemical properties and plant biodiversity inn response to climate change.

Having studied the region's climate and annual rainfall, soil and vegetation sampling was done at a specified time and place in wet (2007) and dry (2018) years based on Standardized Precipitation Index (SPI), taking a specific framework into account0. Inside the reserve, three points were selected as the known sites, digging 10 soil profiles 100 cm deep in the places that had already been determined. Physical and chemical properties such as soil texture, EC, pH, Organic matters, lime, and soil saturation were identified at the soil laboratory. In order to determine the plot size, a minimal area method was used for sampling. In each plot, a list of plant species, density, the percentage of canopy cover, stone and gravel, bare ground and litter were recorded. As for setting the range condition and its trend, four-factor and scale methods were used (Moghadam, 2009). The total vegetation, litter, soil, rock cover, species density and biodiversity indices such as total richness, average richness, Shannon-Wiener diversity index and Simpson dominance index, were also estimated. Furthermore, physical and chemical properties of soil, vegetation cover percentage, and the number of individuals, richness and diversity of two years were compared by the t-test.

The results of the study indicated that after 11 years, the amount of sand, silt and pH increased and clay, electrical conductivity and soil moisture content decreased significantly. Soil texture had also changed from loamy sand to fine sand. It was found that Amiodendron persicum reserve was changed from the hydrologic group B to the hydrologic group A because of drought. Moreover, differences of density, total richness and Shannon-Wiener and Simpson dominance indices were significant at 0.05 and 0.01 between 2007 and 2018. Also, the percentage of vegetation and rock cover, species density, total richness and species diversity showed a significant decrease, and the range condition changed from moderate to poor. However, there was no change in the soil organic material, lime, litter, and bare soil percentage.

The soil and vegetation of the study area have undergone some changes due to wind erosion and the recent 10-year drought, the first of which seems to be the change in soil texture. Actually, the soil texture has changed from loamy sand in 2007 (as wet) to fine sand in 2018 (as a drought). In a similar vein, Zhao et al. (2006) investigated the effects of desertification on soil and crop growth properties in Horqin sandy cropland in Inner Mongolia, north China, concluding that wind Erosion increased soil pH from 8.66 to 8.92, and that soil clay and average soil moisture decreased by 59.6% and 51.8% respectively.The findings of our study suggested also a slow change in the percentage of litter, soil organic matter, and lime, and that drought, except for the average number of species in the plot (average species richness), had a significant effect on other biodiversity indices including the total richness, species diversity, and species dominance, resulting in a decrease in the number of species (total richness). Furthermore, the shannon-weiner diversity index was found between 2007 and 2018. It could be argued that the area has barely been covered by annual and seasonal species due to drought, and there are perennial species such as Ammodendron persicum and Stipagrostis pennata in most sampling plots, leading to an increase in the dominance of Simpson index in 2018.

Supplying good water quality to meet the growing demands of different sectors is one of the main challenges faced by water planners and managers in Iran. The purpose of this study, therefore, was to investigate the trend of changes in groundwater quality in the long run and to calculate and map the quality index of water and nitrate in Zayandehrood sub-aquifers. To quickly assess water quality, a tool should be used to show the amount of water contamination in a short time. To this end, Water Quality Index (WQI) is used to quickly present the water quality assessment, expressing the water quality without mathematical and statistical complexity. The Iranian Water Quality Index (IRWQI) has been developed with the aim of using the appropriate approach to natural conditions and Iran's water resources issues.

some 2935 laboratory samples collected from wet and dry seasons were examined in terms of several water quality indices including EC, TDS, SAR, pH, TH, Cl, CO3, Ca, Mg, Na, K, HCO3, NO3, and heavy elements such as zinc, copper, lead, cadmium and arsenic. The trend of changes in qualitative parameters was evaluated, using MK and TFPW-MK methods whose results showed a decrease in water quality over time. Different interpolation methods were used to map zoning in ArcGIS software. The average IRWQIGC index was calculated in 7 aquifers of Zayandehrood sub-basin, and nitrate zonation and index were determined through kriging method.

The pH parameter displayed a significant negative trend at 1% level in Damanehdaran, Buin Miandasht, Lenjanat, Najafabad and Kron aquifers, at 10% in the forty house aquifer, and at 5% in the Chadegan aquifer. However, in contrast to the negative pH trend, the TDS, EC, and TH parameters showed a positive trendm being significant in the range of Damanehdaran, Buin Miandasht, Chadegan, Lenjanat, and Najafabad. While the anions and cations had no significant trend in the domains of the Damanehdaran, Buin Miandasht and Chadegan, they displayed significant negative trends in the Chehelkhaneh and Kron and a significant positive trend in the Lenjanat and Najafabad aquifers. The results of the study generally indicated a decline of water quality in Zayandehrood aquifer over time. The amount of heavy elements in the aquifer beneath the southern Zayandehrood Basin was reported as being within the permissible range. It should be noted that water is industrially corrosive and in some cases sedimentary. If considered in terms of overall hardness, water is often hard. In this regard, the findings of the study suggested that the highest average nitrate levels in Damanehdaran, Kron and Najafabad aquifers were 48.08, 50.42, and 63.13 mg / L, respectively, wheras the maximum nitrate content in these areas often exceeded the permitted range. Moreover, the lowest values of water quality index were found in Kron, Najafabad, and Lenjanat aquifers which could be classified in bad and relatively bad classes, respectively.

The trend analysis of Groundwater quality showed that water quality in the Zayandehrood sub-basin aquifers declined over time. The managers and planners are, thus, required to take some practical measures in reducing the contaminations exist in those areas. The lowest values of IRWQIGC index were found in Kron, Najafabad, and Lenjanat aquifers, leading to the lower quality of groundwater in these areas. Most of the average nitrate content was reported in the north and northwestern parts of Najafabad, followed by Kron aquifer and the central part of the slopes. Considering the fact that high nitrate rate in some cases mainly originates from the aquifer below the Southern Basin, it could be argued that the agricultural operations in the area would, due to the use of chemical pesticides and water pollution control activities in the area, be contaminated if measured in future. These areas are essential. The aquifers are located below the Zayandehrood Dam. Groundwater aquifers are seriously under pressure, especially on the downstream of the Zayandehrood Basin where water has been permanently off the middle of the river, and dredgers attempt to compensate for water scarcity by exploiting groundwater resources and drilling. As these wells have to compensate for the shortage of water in the region, the quantitative and qualitative decline of water and its pollution is more evident in these areas. A considerable number of researchers have also used the TFPW-MK test in their studies, and many of them have performed qualitative zoning in GIS and regarded kriging method as a suitable method for zoning mapping because the results of kriging are reliable in terms of spatial variance, location, location and sample distribution and then the other ones. Moreover, researchers have been interested in groundwater studies.