مجله مدیریت بیابان
پیاپی 20 (زمستان 1400)

In recent years, droughts, frequent storms, industrial and mining activities have caused a rise in dust in suburbs Tehran, and developing west of the province of Teheran.  The Mallard County is located in the west of the province of Tehran with arid and desert climate and has been selected as the study area. This study aims to determine the soluble metals, minerals and morphology of the original sediments and particulates in Mallard County and to determine the origin of the dust. Dust sediment was collected seasonally at 30 stations using dust collector. Soil and surface sediment sampling were conducted systematically and randomly on 14 pediment and playa facies and a total of 83 samples were taken from the work units. Scanning electron microscope (SEM) was used to determine the shape and size of dust particles, and X-ray diffraction (XRD) identified the minerals found in dust particles. The results showed that most of the chemical compounds in the dust particles consist of magnesium, phosphorus, potassium, iron, chromium, vanadium, nickel, lithium, molybdenum, caesium, scandium, zirconium and titanium. These elements are in the form of quartz, calcite and gypsum clay minerals with a coating of dolomite, hematite and muscovite minerals, with an internal origin that have been transported into the region from close distances or through wind flow. According to the results of the SEM analysis, the particle morphology is angular and semi-circular. Most dust particles can be evidence of the existence of a local and human source and are transported closely.

Mapping of wetlands using remote sensing has faced challenges due to different land cover classes and similar reflectance across land cover classes. Synthetic aperture radar (SAR) data have a special ability to detect phenomena because of their penetration capacity, as well as their independence from time and weather conditionsIn this study, radar data were used to map the land cover of Hamoun wetlands in both wet and dry conditions. For this purpose, L-band capacity has been used to investigate land cover classes. Statistical indicators were used for assessing the separation between land cover classesThe images were classified using the method of the support vector machine. The results of the present study show the capacity of the L-band to separate different land cover classes. The results of the accuracy assessment show an overall accuracy of over 80% in preparing the land cover map of the region. Furthermore, because of the penetration of the L-band, it is possible to detect water in the underlying layer of plants. The results of this study showed that the difference between the reflectance of vegetation that their smaller portion is below the water, and vegetation, most of which is above the water is detectable by the L-band. The difference between their backscatter is 6 dB in the HV and about 2 dB in the HH polarization, which indicates the capaity of the HV polarization to separate these two classes.

One of the ecological crises is the degradation of Nebka's ecosystems that threatens environmental stability and causes many regional and trans-regional impacts, such as increasing the risk of wind erosion. The aim of this study was to investigate the trend of spatial and temporal changes in future land cover with Nebka and accumulated erosive sediments around the phanerophyte species Salvadora persica L. and Alhaji camelorum L. in the Persian Gulf and Oman sea. Thus, Markov chain and satellite images were used to simulate the existing land uses, and trend of temporal and spatial changes. Land cover maps were prepared for the years 2001, 2011, and 2021, using Landsat satellite data and applying maximum likelihood supervised classification method.  After model evaluation procedures, the land cover maps for 2030 and 2040 were predicted using both Markov chain and automatic cell model. Results of land cover changes in 2001, 2011 and 2021 showed that the areas of Nebka have decreased by 1047.9 ha. Predictive maps for 2031 and 2041 with an overall accuracy of 91.4% and kappa coefficient of 0.88%, have high accuracy. The sediment levels of nebka will decrease from 8.67% in 2021 to 4.26% in 2031 and 2.09% in 2041, respectively. The decrease in the area of nebka in the past and predicting the downward trend of changes in nebka land in the future showed that the natural barriers to the movement of suspended sediment were destroyed and reduced.

Due to the importance of halophyte species in the reclamation of saline lands, the present study was conducted to investigating the effects of different levels of salinity on growth traits and enzymatic of Salsola imbricata in a completely randomized design (CRD) with three replications and seven levels of salinity including 3, 10, 20, 30, 40, 50, and 60 dS m-1 at research greenhouse of National Salinity Research Center. Traits of stem length, root length, root-shoot length ratio, collar diameter, number of branches, protein content, catalase, peroxidase, and proline were measured. Results showed that different levels of salinity were significant for all studied traits except peroxidase. Increasing salinity levels from 3 dS m-1 to 60 dS m-1, significantly reduced shoot length at the rate of 20%, root length 30%, root-shoot length ratio 11%, collar diameter 38%, and the number of branches per plant 29%. Increasing salinity from 3 dS m-1 to 40 dS m-1 decreased protein content by 30%, but the protein content increased by 26.7% by increasing salinity up to 50 and 60 dS m1. Results of enzymatic activities showed that increasing salinity significantly increased the amount of catalase, peroxidase, and proline, so the highest of these compounds was observed at 60 dS m1.

Land subsidence is a vertical movement downwards of the Earth's surface. It is difficult to identify or measure because of rapidly depleting ground water. This hazard, as a hydrogeomorphology phenomenon, is revealed in many areas of the country because of the uncontrolled depletion of the groundwater. There are a number of methods for identifying and determining the rate and range of subsidence. Radar interferometry (D-INSAR) technique is known as a robust technique for land subsidence measurement. This method has superior features in terms of cost, accuracy, scale of the study area and time, in comparison with other detection methods, and can provide a precise estimation of the phenomenon. In this study, the Abarkouh plain was studied from January 2016 until February 2018. Sentinel 1 sensor images using radar interferometry technique were used to estimate subsidence. To identify the impact of groundwater extraction in land subsidence, groundwater fluctuations data from 44 piezometric wells, and also land subsidence data were analyzed using regression models. Results showed that the highest rate of groundwater depletion occurred in the town of Mehrdasht and around the agricultural fields, which led to the maximum rate of subsidence up to 12 cm/year. Ccorrelations coefficient between aquifer fluctuations and land subsidence rate is 0.79 that indicated significant relation between these parameters.

It is possible to maintain a stable balance and restore desert ecosystems by growing salinity-tolerant species. In this study, Plantebac moisture absorption plates in establishment and growth Haloxilon ammodendron (C.A. Mey.) Bunge ex Fenzl were used in the Segzi Salt Plain, in Isfahan province from 2018 to 2021. Soil analysis was also conducted before and after the use of plantbac plates. The desired treatments were the irrigation cycle treatment which was considered at two levels of two and four weeks, plant-bac and control treatment. Results showed that the Haloxilon ammodendron seedlings gradually decreased in height, canopy cover and viability.  This decline in growth, size and number of seedlings over the past year compared to the previous years was significant at the level of 1% probability for height and canopy level, and 5% for survival. This is due to unfavourable soil and water conditions in the area in terms of texture and salinity.  The Plantbac plates block the transport of these soil salts to the surface, while irrigation causes the accumulation of salts into the environment around the roots, and thus reduces the growth of Haloxilon ammodendron. The presence of plant-like plates in the soil under the seedlings stopped the capillary flow and as a result, the accumulation of soluble salts in the root zone of the plant, which leads to moisture stress in the plant.