DESERT ECOSYSTEM ENGINEERING JOURNAL
Year:2017 | Volume:6 | Issue:15 |Papers Count:10

Temperature is an important environmental factor in plant distribution and the most important factor in determining the success or failure of seedling establishment. The aim of this study was to investigate the effects of different levels of gibberellic, salicylic and ascorbic acid on improvement of germination indices of Zygophyllum atriplicoides under temperature stress in laboratory. Factorial test in the completely randomized design with four treatments was used for data analysis. Chemical stimulators used in this study include: 3 levels of gibberellic acid (125, 250 and 500 ppm), 3 levels of salicylic acid (100, 200 and 300 mg/l), 3 levels of salicylic acid (100, 200 and 300 mg/l) and 6 levels of temperature treatment (5, 10, 15, 20, 25, 30°C). The results showed that with increasing temperature, specifications for germination (germination percentage, speed of germination, root length, shoot length, seedling length, vigor or seed) also increased. When the temperature reached 25°C, the maximum amount of chemical stimulators is obtain and decreased with increasing temperature from 25 °C. All chemical stimuli increased germination compared to the control treatment. Chemical stimuli used in 250 ppm gibberellic acid was the most effective acid concentration to modulate the negative effects of temperature stress on Z. atriplicoides and is recommended.

Today, climate change and global warming caused by the emission of greenhouse gases is a big challenge to the world, especially in arid and semi-arid area. Afforestation is the most effective strategy to absorb carbon dioxide in terrestrial ecosystems and reduce global warming of the earth. The purpose of this study is to evaluate the effects of planting Eucalyptus camaldulensis and Amygdalus scoparia on carbon sequestration and some soil properties in Dashte Mazeh forest park of Dehdasht, southwest of Iran. For this purpose, soil samples were taken by the systematic-random method from depths of 0-15 and 30-15 cm. After measuring the soil chemical and physical properties inclusive of clay, sand, silt, pH, electrical conductivity, phosphorus, potassium and organic carbon in the laboratory, the data were analyzed with Orthogonal Comparisons method, using statistical software SPSS 20. The results showed that the soil carbon sequestration in forested area and non-forested area was estimated to be 20.8 and 8.73 t/ha, respectively (P<0.01). In addition, the rate of carbon sequestration, soil organic carbon and potassium in the Eucalyptus stand was more than that of Amygdalus stand (P<0.05). The results have shown that soil depth had no effect on carbon sequestration and other soil properties. The results of correlation analysis showed that there were positive correlations between soil organic carbon with percentage of clay, silt and potassium and negative correlation with sand.

Sand dunes in central Iranian habitats contain endemic shrub species and adapted shrubs of the family Fabaceae, known as Smirnovia iranica Sabeti. Not only are these very important for forage production and soil conservation, they also help create beautiful landscapes. They also possess medicinal value. This cytogenetic study was carried out on four sites in the sand dunes of Kashan within a distance of 30 km. From each habitat, a plant was selected, and the seeds harvested. Seeds and root samples were prepared for examination with high-resolution photos to view the mitotic metaphase chromosomes and measure the karyotype parameters, using Micro measure 3.3 software. The results showed that this plant is diploid (16=x2=n2). The largest chromosome was Chromosome 1 of Camp 1 site (15.6 m) and the smallest was Chromosome 12 of Camp 2 site (12.2 m).

Environmental crisis and the consequent loss of natural resources are the main reasons which force managers to pursue methods to manage risks and solve environmental tensions. This study was conducted in Samad-Abad as a center of wind erosion located in the southern part of Sarakhs region, Islamic Republic of Iran, near the Turkmenistan border and the Tajan River. Following field investigations and satellite imagery analysis, the study area was determined. Using 6 transects (3 upwind and 3 leeward), each 100 m long, we measured nebkhas’ morphometric characteristics (including height, length & volume) and plant characteristics (including height, perimeter & volume). Fourteen nebkhas were analyzed for each species (Stipagrostis, Alhagi and Peganum). In a comparative analysis of nebkhas associated with Stipagrostis, Peganum and Alhagi using TOPSIS model, the final weight was calculated as 0.434, 0.521 and 0.055 for Alhagi, Peganum and Stipagrostis, respectively. Therefore, as clearly explained by the TOPSIS model, Peganum is revealed to be the most suitable plant species for stabilizing moving particles in the region followed by Alhagi and Stipagrostis. Regarding nebkhas’ morphometric characteristics and plant morphological features as the input criteria for AHP model, the results showed Peganum to be the most suitable species for stabilizing moving sands followed by Alhagi and Stipagrostis. Stipagrostis nebkhas, with an average weight of 0.073, showed the least efficiency and desirability. Therefore, it was concluded that the observed result was due to this species’ undesirable morphological traits compared with the two others species in the study. Consequently, developing the landscape cover by this species is not advised.

Wind is one of the important natural phenomena in arid and semi-arid ecosystems of the world. Although several studies have been conducted using the wind speed and direction to provide wind rose in each area, only a few of them investigated the possibility of wind speed at different return periods. Analysis of the maximum wind speed at different return periods, in a variety of projects such as the construction of high-rise buildings, windbreaks, billboards along highways and all structures that are expose to wind, will be used to calculate risk-taking. In this study, using data from maximum wind speed of 22 synoptic stations in Iran in the centrality of Yazd province and by using the P10 software, maximum wind speed was estimated in the return periods of 2, 5, 10, 25, 50 and 100 years. By examining the Normal, Lognormal, Pearson, Log Pearson and Gamble statistical distributions, it was found that the Gamble distribution in 56% of stations have the lowest standard error and so it is more efficient. Then, with the method of ordinary kriging interpolation on Surfer 13.4 software, maps of wind speed at different return periods were prepared. The results revealed that the strongest possible winds in 100 years return period belong to Eghlid (59.9 m/s), Sirjan (47.3 m/s), Shahreza (43.1 m/s), Kabootarabad (42.8 m/s) and Natanz (41.6 m/s) stations. On the other hand, wind speed at different return periods in the west areas of the region has more intensity and the main reason can be described by synoptic conditions and local topographic corridors. Also, relations governing the temporal distribution of wind speed, indicated logarithmic relationship between speed and different return periods.

Today, degradation of soil and water resources are the most important factors of desertification in arid and semi-arid areas as a result of mismanagement and improper human behavior. Enforcement measures in relation to desertification control have to be based on knowledge of the current state of desertification risk and its severity. In the present study, to evaluate the risk and severity of desertification in Bostaq Plain in Southern Khorasan Province, two key criteria of water and soil were used in the IMDPA model, each having four indices. To this end, indices were scored and then averaged (geometric mean) to form the final desertification map in Arc GIS 10.2. Results of the study showed that in terms of water criteria, electric conductivity (EC) with geometric mean of 3.33 and in terms of soil, surface stone cover with mean of 2.69 were the critical desertification indices in the region. Total desertification status could be further divided into two classes of 96.29% (22111.74 ha) as medium and 3.7% (849.63 ha) as severe. Generally, Bostaq Plain with geometric mean of 2.13 was in the medium desertification class and is due to protection and development of desertification management strategies which can reduce the effects of desertification and should be implemented in managerial practices in the Bostaq plain.

Recently, scientists are concerned about nuclear waste landfill sites. Because salt pans, salt marsh and salt domes are non-porous environment, with no stubble thickness of salt and the plant communities, less humans and animals can be found around them, so it can be used as a nuclear waste landfill. In this study, 24 environmental criteria are investigated with emphasis on hydrology, watershed management, geological structure and socio-economic situations that included: slope, drainage density, maximum instantaneous discharge, drainage class and other parameters. Then, the criteria were evaluated using questionnaire and consultation with experts. The lowest and the most important criteria were related to maximum instantaneous discharge and distance from residential areas with 0.031 and 0.052 value, respectively. In ELECTRE model, all options were evaluated by non-ranking relations and in this way, non-effective options were eliminated. At first, by calculating numerical values, all criteria were given in the form of a matrix, which is called decision matrix. Then data of the decision matrix values which are non-scaled and criteria values were entered in the matrix. Thereafter, the effective coordinated and uncoordinated matrixes and consistent matrixes were obtained and finally, final matrix is formed. According to ELECTRE model results, it could be possible to prioritize three salt domes of southwestern Hormozgan for burying nuclear waste. Gachin salt dome, with most indices (1), as the most suitable option and Angouran salt dome, a numerical index (0) and Pol salt dome, with an index number (-1), ranked second and third, respectively.

Drought monitoring is one of the key factors in drought risk management and the use of drought indices such as the standardized precipitation index (SPI) is a useful tool in this regard. The aim of this study is to evaluate and zone drought risk in different years and return periods in Karkheh basin. For this purpose, Standardized Precipitation Index (SPI) as a selected index was used to assess drought in 33 stations inside and outside the basin in five timescales. The results showed that the lowest values of SPI, the most severe drought continuity of the large and the longest continuity were related to Govar stations of Kermanshah province, Biderood station of Khoozestan province and Jokar station in Hamadan province, respectively. Extensive drought risk maps for different return periods showed that in return period of 5 years, northern (Bavane station of Kurdistan province), northeast (Hamadan station) and northwest (Kermanshah) areas were more at risk of drought. This condition for a return period of 10 years was mostly related to northern (Bavane station of Kurdistan province), northwest (Kermanshah) and central areas. Drought risk for 20-year return period affected the northern (Bavane station of Kurdistan province) and Northwest (Kermanshah) areas more, while for 50-year return period, in addition to northern (Bavane station of Kurdistan province) and northwest (Kermanshah), it also affected the northeast (Hamadan station). The overall result showed that the periphery areas, especially areas of northwest, north, northeast and some parts of eastern and southeastern areas are the most susceptible areas affected by drought and with increase in the return period, the severity of drought risk can be reduced.

Monitoring of Meteorological and groundwater droughts and determining of the lag time between these two types of droughts in spatial various locations can help in consumption management and protection of the groundwater resources. In this study, spatial and temporal changes of droughts were analyzed using the Standard Precipitation and Groundwater Resource Indices (SPI & GRI) in the northern Mahyar plain located in Esfahan province. The results showed that groundwater drought in most areas of the aquifer have occurred with a longer lag time (48 months). This is due to increase of groundwater depth and probably due to decrease permeability and blocking pores of the alluvium formations as a result of high number of exploitation wells and heavy withdrawal of groundwater resources in the area. In the western part of the aquifer, particularly around the Ajrakh piezometer, there were high correlations between meteorological and groundwater droughts in lag time of 24 months with R2 value of 0.62. In this part of the aquifer, the factors that make relatively fast response of groundwater level to precipitation fluctuations were the high permeability coefficient, input flows from the adjacent aquifer, lateral recharge caused by permeable limestone formations close to the plain, keeping of aquifer effective porosity and control of subsidence phenomenon due to transferred water from Mahyar channel. Also, the results of spatial mapping of meteorological and groundwater droughts showed increase in the amount of lag time between meteorological and groundwater droughts and expansion of drought severity in most parts of the aquifer over time.

Evapotranspiration process is a key element in hydrological simulation of water supply, rainfall-runoff models, infiltration calculations and drought prediction models. Recently, several equations were used for estimating annual, monthly and daily evapotranspiration in the world. In this study, the potential evapotranspiration of Taleghan watershed was estimated by three methods in the SWAT model including Priestley Taylor, Penman-Montieth and Hargreaves methods. The influence of applying these methods were evaluated on simulated stream flow of the Taleghan watershed in the calibration (1998 - 2003) and validation (2003 - 2005) periods, using determination coefficient (R2), root mean square error (RMSE), Nash–Sutcliffe performance coefficient (NS) and skew index (PBIAS). Results revealed that the maximum and minimum values of simulated evapotranspiration and consequently, simulated runoff were related to the Hargreaves and Priestley Taylor methods, respectively. Moreover, investigation of statistic coefficients showed that there is no much difference among the three methods. Results of ANOVA also confirmed that there was no statistically significant difference at the 99% level among the simulated mean monthly flow using the three methods. In conclusion, the Hargreaves method provided better results than the two other methods during calibration and validation periods.