Desert
Volume:24 Issue: 2, Summer-Autumn 2019

This study was an analytical research across 84 meteorological stations, performed in the Mighan sub-basin over a fifty-year study period (1961–2011).This research seeks to answer the basic question of how declining streamflow, increasing temperatures, and fluctuation in precipitation have impacted water resource allocation in the Mighan sub-basin. The research method is analytical based on Mann-Kendall method. Analysis of independent flow measures (discharge and groundwater levels) using the Mann-Kendall trend test suggests evidence for climate change trends for many of the 84 stations. The results highlighted a mix of positive (increasing) and negative (decreasing) trends (monthly, seasonal, and annual) in the Mighan sub-basin. The results showed that during the 10-year period (1961-70), the minimum temperature occurrence in the first decade at -33.5 ° C (1973) and the maximum temperature event in the same decade at 57 ° C (1974) made this decade one of the most volatile decades in a fifty year period. Despite the inter-annual climatic fluctuations, results revealed that the Mighan Sub-basin has encountered many severe fluctuations of precipitation and average annual discharge during the five decades.

The United Nations’ convention on desertification encourages the participating countries to introduce criteria for developing Early-Warning Systems (EWS) in order to monitor and assess desertification. The objective of the present study was to establish an EWS for desertification assessment in Kashan plain, Iran, using the methodology of practical and general applicability. Designing EWS requires a model to identify the influential criteria and areas vulnerable to desertification. The Kashan Plain’s EWS relies on the Iranian Model for Desertification Potential Assessment (IMDPA) to establish desertification thresholds and generate desertification maps with Geographic Information Systems (GIS). The EWS of Kashan plain was designed to calculate hydrologic (groundwater level and electric conductivity of groundwater indices) and climatic (precipitation, Transeau aridity, and drought indices) criteria and assess the degree of regional desertification.  Afterwards, the desertification intensity maps of criteria and indices were produced and overlapped. The EWS was developed in areas most bound to be threatened by desertification. EWS quantifies desertification data and thresholds to issue desertification assessments and warnings for management purposes. In the next step, Client–Server program was designed based on an algorithm defined by Java programming language and implemented as a data collection, analysis, and response management system. Whenever the thresholds exceed the defined limits, warning messages can be sent via SMS or internet to relevant system managers for appropriate action.

Aerosols affect the earth's atmospheric radiative fluxes via direct, semi-direct, and indirect mechanisms. Aerosols also are one of the main sources of uncertainty in climate models. In the Middle East, in addition to climate effects, various problems such as reduced visibility, human health hazards, and air pollution are caused by aerosols. Studying the optical and physical properties of aerosols on local and global scales helps reduce the uncertainties in climate forcing. In this study, aerosol optical properties, including Aerosol Optical Depth (AOD), Angstrom Exponent (AE), ASYmmetry parameter (ASY), Single Scattering Albedo (SSA), and phase function were analyzed. These properties were investigated over five sites in the Middle East during 2013 using the Aerosol Robotic NETwork (AERONET) data. The results revealed an inverse relationship between AOD and AE in all sites. A high AOD value and a low AE value were detected in spring and summer in all studied sites, suggestive of coarse mode dust particles. ASY initially decreased due to the dominance of absorbing type aerosols in the visible spectrum with the increase in wavelength. Afterwards, ASY increased with the increase in wavelength in the infrared region due to the dominance of the coarse mode particles. In most sites, SSA increased, particularly in spring and summer, with the increase in the wavelength because of the dominance of desert dust. In spring and summer, the phase function was high over all sites. High phase functions associated with small scattering angles were caused by the coarse mode particles.

Salinity is a major environmental stress negatively influencing germination and seedling establishment in a wide variety of crops. The objective of this study was to use the organic materials with superabsorbents to improve the emergence rate and seedling traits of Milk thistle (Silybum marianum L.) under salinity stress. A factorial experiment in a completely randomized design with three replications was conducted in outdoor pots. Treatments included: organic coats at two levels (C1= peat moss and C2= vermicompost), superabsorbent polymers at seven levels (A1= without superabsorbent, A2-A4= coats with 2, 4, and 6 g superabsorbent of A200 per kg organic material, and A5-A7= coats with 2, 4, and 6 g superabsorbent of F1 per kg organic material), and salinity (S) stress at five levels (0, -2, -4, -6, and -8 bar). Results showed that organic material and the type and amount of superabsorbent significantly (p ≤ 0.05) affected emergence, emergence rate, plant vigor index, shoot dry weight, leaf area, specific leaf area, relative water content, and total chlorophyll. Application of superabsorbent polymers with organic material reduced salinity stress in the primary growth stage of Milk thistle. Generally superabsorbent A200 is more effective than superabsorbent F1 and vermicompost coats better are than peat moss coats.

Desertification is a serious ecological, environmental, and socio-economic threat to the world, and there is an urgent need to develop rational methods for its evaluation at different spatio-temporal scales. This study aimed to address the main directions of desertification changes in Semnan County, Iran. Monthly precipitation was used to calculate a 12-month SPI (Standardized Precipitation Index) and the normalized difference vegetation index (NDVI) obtained by LandsatThematicMapper (TM) sensor of April month were used for the three years, viz., 1987, 1998, and 2011. Five major categories were identified at level-I and they were subdivided into 11 categories including, 1. Residential areas, 2. Vegetation, 3. Bare and rocky areas, 4. Salt lands and 5. Sand areas. The results indicated that the reduction of the NDVI values was consistent with the changes in land use/land cover. This progress was taken place in some areas with the development of bare soil to salt land, and in some areas with the expansion of sand land, particularly from 1987 to 1998. The results indicated that the salt lands increased 348.24 and 721.57 square kilometers from 1987 to 1998 and from 1998 to 2011, respectively. The results revealed that desertification occurred at a rapid rate, especially towards the east and southeast directions in the study area. That was, towards the Dasht-e-Kavir and Damghan City. The results showed that besides using NDVI and SPI for drought monitoring, the meteorological variables such as temperature, sunshine hours and evaporation could improve the accuracy of interpretation of the results.

Creating water-conserving turfgrasses using superabsorbents in soil is a challenge especially in arid environments because their related soil and plant’s behavior is still less known. This research investigated soil moisture content and physiological characteristics of Lolium perenne L. ‘Chadegan’ (perennial ryegrass) and Festuca arundinacea (tall fescue), in the absence (control treatment) or presence of four superabsorbent types. The superabsorbents were Zeolite (zero and 10% wt), Bentonite (zero and 6%wt), Aquasorb (zero and 6 g/m2) and Boloorab (zero and 50 g/m2). The experiment was factorial based on a randomized complete block design with four replications. A one-month stop on irrigation occurred after the first five-month full irrigation regime to simulate drought stress conditions. The results showed tall fescue had higher leaf relative water content, lower relative electrolyte leakage and lower relative saturation deficit than that in perennial ryegrass after applying the drought stress. However, tall fescue had higher chlorophyll content than this factor in the ryegrass. Aquasorb and then Bentonite were able to improve the fresh weight and dry weight in roots and shoots under drought stress conditions compared to the control treatment. Using Aquasorb was associated with better physiological characters in the turfgrasses and higher water content in the soil. Overall, under drought stress conditions, planting tall fescue in a soil containing Aquazorb promised a better quality turfgrass for urban green spaces.

To understand and manage the natural and human-made ecosystems and develop long-term planning, it is necessary to model Land Use Change (LUC) and predict future changes. Therefore, we used Landsat satellite imagery, Multilayer Perceptron neural network (MLP) and Markov Chain model (MCA) to monitor the regional changes over 30 years in the central arid regions of Iran. In the present research, the stratified maps derived from the object-oriented algorithm were used to detect and map the changes of land use classes from 1986 to 2016. Furthermore, the land use in 2030 was predicted using Land use Change Modeler (LCM). Slop, contour elevation lines, distance from river, road, afforestation, agricultural lands/gardens, barren lands, poor rangelands, residential lands, rocky land, and sand dunes were considered as factors influencing the changes in the ANN. The Cramer's V coefficient was employed to select appropriate parameters with the highest significant correlation. Our results showed that the sub-models performed well (75-85%). Besides, the highest and lowest accuracy of sub-models were related to the distance from barren lands and distance from residential areas (75.23 and 85.91%, respectively). The results of land use change monitoring from 2016 to 2030 revealed that land use such as forest, residential lands, gardens, and sand dunes would be increased by about 0.11, 1.53, 2.36 and 0.56 %, respectively, by 2030 compared to 2016. On the other, the area of barren land and poor rangeland would be reduced by 2.88 and 1.68 %, respectively. Our results can be used in land change evaluations, environmental studies, and integrated planning and management regarding appropriate and logical use of natural resources and reducing resource degradation.

The water, a built environment, and a palm grove are an impressive trilogy making up the formidable oasis, rendering it strong enough to survive the harsh desert climate. Furthermore, the interaction between them creates several natural and physical phenomena. This research discusses the oasis effect, one of the most significant phenomena in the oasis ecosystem; this effect has been treated as a cooling phenomenon in theories and mathematical models. Therefore, we aimed to examine the impact and limits of this phenomenon in regard to the microclimate of oases through digital simulation, using the SPUCAL_oec software (Simulation Platform of Urban Climate in Arid Lands _ Oases Effect Calculator).  Based on an innovative mathematical model, we developed SPUCAL_oec as an innovative vision for this green phenomenon, programmed to predict, calculate, and simulate the behavior and limits of the palm grove on the oasis microclimate. Finally, the results of SPUCAL_oec model showed that the oasis effect impacted the oasis microclimate owing to the existence of the palm grove. This effect could be as large as 6°C of temperature decrease and 12% increase in relative humidity. Furthermore, the SPUCAL software can aid designers and planners in making decisions regarding their design process.

Accumulation of secondary calcium carbonates in arid and semiarid regions is a valuable tool for evaluating the degree of soil evolution, soil age, palaeoenvironmental reconstruction, and soil classification. In particular, laminated pedogenic carbonate pendants are able to provide evidence regarding local environmental and climatic changes. In this study, calcitic pendants from semiarid soils of Rashakan region (West Azerbaijan province, Iran) were investigated. Rashakan region is composed of four physiographic units, including mountains, hills, plateaus, and piedmont plains. A transect of four soil profiles was studied micromorphologically. Based on micromorphic observations, carbonatic pendants are present as mammillary to botryoidally stalactite-like masses, growing downwards from the bottom of coarse fragments. They are multilayered and comprised several light and dark-colored layers, indicating the differences in calcite precipitation conditions. Sequences of light and dark-colored lamina of pendants probably represent climatic changes. We propose that light-colored lamina with relatively pure calcite are precipitated in dry periods that climatic conditions are not favorable for biological activities. However, dark-colored lamina, consisting of calcite mixed with clay and organic impurities, are formed in relatively wet periods with better conditions for biological activities. Therefore, the sequence of light and dark-colored laminae can reflect climatic variations and be employed as a tool for palaeoclimatical and palaeoenvironmental studies.  In the structure of some pendants, there exist some fractures and voids between pendant and skeletal grains. Accordingly, these pendants must be considered for palaeoclimatical and palaeoenvironmental reconstructions.

The main purpose of this study was to analyze the effective factors in sustainable management of forest resources (SMFR) among local communities. Given that forested areas form a major part of Faryab county, the focus of the present study was on natural resources which forested lands of the is located in rural district of Mehruyeh. Statistical population included all the exploiters in Mehruyeh village utilizing forest resources (N=7000). The sample size (173 individuals) was obtained using Cochran formula sampling technique based on simple randomized sampling method. The research instrument was a questionnaire which validity and reliability were confirmed by an expert panel and Cronbach's alpha coefficient (α>0.7). Data analysis was conducted using SPSSwin18 and Lisrel8.54 whose results showed that the most important destructive causes in the village were overgrazing and deforestation to create arable lands; furthermore, most of the studied exploiters followed sustainable management of forest resources at a low level. Also, there was a significant difference between sustainable management of forest resources and variables age, forest working record, education level, and the kind of forest exploitation system. The correlation analysis results showed a significantly positive relationship between political-supporting factors, psychological-training factors, cultural-social factors, economic-supporting factors, and sustainable management. Moreover, regression results indicated that the foregoing factors accounted for 78.9% of variance changes associated with sustainable management of forest resources.

Urbanization is developing unprecedentedly on a global scale. One of the chief repercussions of urbanization, caused by man-made alterations in land-use/land-cover (LULC), is the formation of urban heat islands. Albeit, differences among landscape structures and its accompanied effects on the environment are mostly neglected. Accordingly, the main objective of this study is to survey the various effects of LULC on urban heat island in terms of landscape metrics. For this purpose, Landsat-8 images and land-use maps extracted for the study region (Urmia) were employed. Landscape metrics were calculated from Landsat images with spatial resolution of 30 m for five varying scenarios (residential lands of five-floors and more, residential lands with less than five-floors, administrative-commercial lands, industrial lands, educational and health lands). The metrics were then investigated with respect to two types of land-cover (vegetation and impervious lands). Analysis results indicate that following industrial use, administrative-commercial use is the most significant factor contributing to the formation of heat islands. Results also stipulated the indirect relationship between vegetation and land surface temperature for all scenarios, with the exception of industrial use; in contrast impervious surfaces showed a direct relationship with earth temperature. Study results further determined the effectiveness of human factors in conjunction with LULC as amongst key factors influencing urban LST. Finally, the study specified how different effects of LULC on heat island of Urmia can be well defined with reference to landscape metrics.

The current study was conducted to investigate the effect of tillage methods, residue rates, and forward speeds on the soil-water characteristic curve (SWCC) of Haploustepts soil over the course of one crop year (2014-2015). The treatments consisted of conventional mechanized tillage (CT: moldboard plough+disc) and reduced tillage (RT1: chisel peker+plough and RT2: combined tillage), different surface residues, including three levels of no residue, 40% residue, and 80% residue, and forward speeds at three levels: low (4 km/h), normal (7 km/h), and high (10 km/h). The experimental water retention data were fitted to uni-modal van Genuchten (termed uni-modal vG) and bi-modal Dexter (termed bi-modal Dex) models. No significant impact was observed on different physical parameters, except for parameter n. In the slope at the inflection point of SWCC, 11.8% and 8.9% reductions were observed in CT and RT1 treatments, respectively, compared to RT2. Based on the results,  measured under CT tended to be higher than that of other tillage treatments. Residual covers and higher forward speeds tended to increase both  and . Changes in PSD were more pronounced in larger (macro) and medium (meso) pore diameter classes. The highest value of structural void ratio as transmission pores was observed in RT2. This finding indicates that with respect to , , , and  values, the soil PSD descriptive system is a bi-peak distribution such as H-L; therefore, due to the hierarchical nature of soil structure, van Genuchten equation cannot appropriately describe multi-modal soils inherently.

Hydrological status and water table fluctuations are directly related to land use and/or land cover (LULC) changes in each area. In this research, the impact of LULC changes on groundwater quantity and quality of Khan-Mirza Plain, in the northern Karun watersheds, was investigated. For this purpose, Landsat 5, 7 and 8 satellite images and ETM and OLI sensors were employed to prepare the LULC map of Khan-Mirza Plain for 2006 and 2016 using the artificial neural network algorithm. The neural network algorithm with the general accuracy of 90/29 was classified into six use classes (agriculture, rangeland, residential areas, rocky and bare lands, gardens and lowlands). Analysis of changes indicated that agricultural and residential uses were increased, respectively, by 62.5% and 3.5%. The biggest change was in conversion of the rocky and bare lands for the agricultural use. Another change was in the LULC of rocky and bare lands and rangelands: these have been converted into to the residential areas. A few piezometric wells in the plain were also used to investigate the lowering of the groundwater table during the 2006- 2016 period. The quality parameters investigated were calcium, sodium, magnesium, potassium, all soluble solids, electrical conductivity, sulfate, chlorine, bicarbonate, and water acidity (PH). Investigation of the time variation of the groundwater quality parameters further showed that potassium, water acidity, and bicarbonate followed an upward trend during the studied time. Most chemical parameters of water had the highest concentrations in the central plain area. The results, therefore, showed that increase of degradation and growth of human activities in the region had both caused changes in the LULC, subsequently intensifying the quantitative and qualitative loss of groundwater in the Khan-Mirza Plain. Therefore, the areas with irrigated agriculture, dry farming, and undeveloped agriculture have been increased. One of the main reasons for lowering of water table in 2016 was the excessive exploitation of groundwater as a result of the change in agriculture uses.

Soil and desert varnish are powerful records capable of saving invaluable data regarding environmental factors and processes during their formation stages. The present research was carried out to identify the environmental variations and paleoclimate reconstruction in the central deserts of Iran using soil and varnish micromorphological characteristics. Mantled pediment, alluvial fan, and alluvial plain landforms were selected. A minimum of one representative pedon was described and sampled on each geomorphic surface, amounting to a total of eight pedons. Varnished rocks were further collected from all geomorphic surfaces and studied by petrography microscope. Clay (coatings and micro layers), calcite (nodules, coatings, quasicoatings, and infillings), anhydrite (nodules), halite (coatings) pedofeatures, clay coating-calcite infilling, and anhydrite nodule-clay coating compound pedofeatures were investigated in the thin sections of the soil. Lenticular, vermiform, and platy gypsum crystals were identified as nodules and interlocked plates. Desert varnishes (100-600 µm) were different from host rocks as far as color, texture, and formative components are concerned. According to micromorphological evidence, the area probably experienced two different climates. Coatings and infillings of clay in soils and rock crevices were developed in an environment with more available humidity. Evaporite minerals were formed in soils and clay coatings on rock surfaces in the following period with less available moisture. The study results showed that micromorphology could be a necessary and useful tool in pedology and paleopedology investigations.