جستجوی مقالات مرتبط با کلیدواژه « arid areas » در نشریات گروه « آب و خاک »

Due to the environmental problems caused by wind erosion, it is necessary to stabilize the dust centers with mulches. The objective of the present study was to determine and compare the optimum vinasse mulches based on mechanical indicators for sensitive soil stabilization to wind erosion. In this research, vinasse (0, 100, 200 g) is combined with bagasse (0, 25, 50 g), ash bagasse (0, 25, 50 g), filtercake (0, 12.5, 25 g), and one-liter water (81 treatments). At first, the treatments were determined in the appropriate range of salinity and acidity (35 treatments) and in the next step, the mechanical indicators have been measured after mulching on laboratory trays (2×30×100 cm). Optimum mulches have been determined based on five indicators by mean comparison (Duncan). The mean comparison showed that treatments 33, 30, 34, 32, and 19 show the mean difference between the groups based on layer thickness, impact resistance, compressive strength, and shear strength properly. It can be concluded that vinasse (100 and 200 g) with 50 g bagasse reduces the crack coefficient greatly, and the application of vinasse, bagasse, and filtercake does not affect the compressive strength and impact resistance.

Stability of soil structure is one of the most important indicators of land degradation sensitivity and soil quality. Also, soil salinization is among of the main causes of land degradation in arid and semi-arid regions and the critical factor limiting agricultural production (Arasto and Akhiani, 2018). Soil salinity affects plant growth and in this case, the importance of soil is determined due to increasing population growth and the emergence of new needs for more food (Karam et al., 2018). Drought as a natural disaster and inevitable phenomenon has been seen in a wide range of countries, especially countries located in arid and dry regions of the world (Saeidipour et al., 2018). 

In order to investigate the role of drought in intensifying soil salinity in Kashan Plain, drought periods were studied by standardized precipitation index (SPI) in six time periods in the statistical period 2000 to 2017. The results indicated that the years 2000, 2008, 2015, and 2016 were the reference years with the maximum intensity of drought. Salinity changes in reference years were analyzed using the salinity index (SI) obtained from satellite images, ETM + sensors through ENVI software (version 7.4). Then, the ground reality map of soil salinity was obtained by field sampling, laboratory studies, and interpolation in ArcGIS software (version 10.4.1). According to the root-mean-square error (RMSE) criterion, the inverse distance weighting (IDW) method was selected as the most suitable interpolation method in spatial mapping of drought intensity. 

The results of the correlation analysis showed that there is a significant relationship between the actual and intermediate salinity values ​​at the level of 1% with a correlation coefficient of 0.968. This suggests that the obtained model is a good estimator for soil salinity prediction. The results also showed a significant correlation at the 1% level between drought and EC using the Spearman method. The results showed that increasing drought will increase the salinity amount, although this relationship was found inverse for 2016. 

The characteristic arid zone has a variable climate; so that these climatic fluctuations have made it prone to high sensitivity. Over the past few years, reduced rainfall and increased temperature in the Kashan Region have been the main causes of soil salinity. Along with the occurrence of meteorological drought, over exploitation of groundwater and the entry of solutes through precipitation are intensified the soil salinity over the study area.

With respect to water shortage during the recent decades, subsurface irrigation method has been considered in arid and semiarid zones. Therefore, experimental design was performed as completely randomized blocks with four repetitions in Isfahan University of Technology. Then, the effects of different irrigation intervals of every day, every other day and once a week under the surface and subsurface irrigation on height, collar diameter, chlorophyll content and stomata conductivity of Zygophyllum fabago L. were investigated. The percentage of plant survival was also recorded six months after planting. The results showed that irrigation interval had a significant effect on height, chlorophyll content and stomata conductivity of the tested plant (P<0.05) and the height, diameter of the collar and stomata conductivity decreased by increasing the irrigation interval. While, the irrigation interval didn’t have a significant effect on the collar diameter (P>0.05). The highest percentage of survival (100%) was observed in subsurface irrigation treatment and control treatment had the lowest percentage of viability (70%). It could be concluded that the improvement of growth parameters and survived of Zygophyllum fabago were better with the subsurface irrigation than the surface irrigation.

Water consumption has been rising during the last five decades across the globe because of population growth, higher standard of living, and economic development. Water resources limitations in Iran has led to the emergence of sustainable water resource management. To deal with the complex and interlinked water challenges, we need knowledge about the quantity and quality of water in the watersheds through water balance investigation. Evaluating available water resources is a prerequisite step in the water resources management to avoid adverse environmental impacts. Water balance investigations, as a tool for quantitative evaluation of water resources, is a prerequisite step in water resources management process. However, we have faced to some problems with water balance calculations such as: it is costly and time-consuming to provide reliable data for a large area and the estimation methods of water balance components rely on the methods that would not be appropriate for Iran's meteorological, hydrological and hydrogeological conditions. For example, in many cases, the empirical methods and mathematical models used in Iran were developed in other countries with different climates.

Water balance models have been developed over multiple timescales (hourly, daily, monthly and yearly) and different spatial resolutions and varying degrees of complexity. Water balance models were first developed in the 1940s by Thornthwaite. With the increasing use of water balance models to address hydrological problems, a considerable amount of efforts has been devoted to the development of such models and techniques. A variety of models have been considered, ranging from relatively complex conceptual models to complex physical based models. Previous studies showed that using conceptual water balance models rather than process-based models or data-driven models have some advantages. Process-based models require high resolution, in both space and time, data and data-driven models may not remain valid in changed climatic conditions. Therefore, we focus on distributed and semi-distributed mathematical conceptual models. After evaluation different models, we introduce and classify some models that have relative advantages for being applied in Iran. These models have at least one of the following properties: they are conceptual models, some of them have been used for different regions, and some of them have been used for dry and semi-arid areas, and they use a simple method for water balance calculation, or their code, software or graphical interface are available freely.

To choose and modify an appropriate water balance model for Iran's watersheds, we should consider a simpler one especially when there are usually uncertainties about the model parameters and input data due to sparse data and lack of knowledge about the natural systems. We investigated different models especially models that have a fewer number of parameters for calibration and consider hydrological spatial variability in a water basin. Considering these facts, it seems the model developed by Portoghese et al. could be a good choice for the most arid and semiarid regions in Iran, after necessary corrections and modifications. The modified model was successfully implemented in different watersheds in Razavi Khorasan province. The model results, such as runoff, actual evapotranspiration, and deep percolation were in agreement with other studies, and consistent with the basin hydrological process.

Increasing aridity caused by the drought phenomenon in recent years has led to a decrease in the threshold wind speed for removing dust particles from the soil surface of arid areas. The accumulation of salts on the surface of the soil, due to low precipitation and high evaporation, causes disintegration of the aggregates. Salt particles along with the soil particles are removed by wind and they fall over a distance. If the target area is agricultural land, dust containing salt results in the transfer of salt to the affected area, which leads to a decrease in the yield of the crops. In this research, EM38 electromagnetic induction instrument was used in horizontal orientation in order to provide a cheap and fast map for surface soil salinity (0-30 cm) in the area that are sensitive to wind erosion in northern Yazd-Ardakan plain. The ESAP-95 2.35R Software package was also used to determine the number and location of soil samples in order to determine the regression model and to prepare a map of the salinity pattern in the area. With the transfer of EM38 data to the ESAP-RSSD program, the standard number and soil sampling points for 12 sites were identified. Subsequently, a Multiple Linear Regression model (MLR) was developed using ESAP-Calibrate and using Electrical Conductivity data of the saturated extract (ECe), saturation percentage (SP) and percentage of water content (WC). The results showed that the proposed regression model could model the soil surface salinity from EM38 readings with a determination coefficient (R2) of 0.37 and Root Mean Square Error (RMSE) of 80.55. The results of using the ESAP-SaltMapper program for mapping soil surface salinity showed that the southeast of the study area had higher salinity and the possibility of harvesting salt by the wind was much higher. The results also showed that the use of the EM38 device should be made in areas with homogeneous and standardized moisture at field capacity level and ESAP software can be used to map soil salinity.

Water shortages has always been a great concern as a limiting factor for agricultura l production in Kerman province. Rainfed sowing may be recommended to bypass the problem. Because of high rates of potential evapotranspiration and limited water resources in arid and semiarid areas, it is expected more attention will be paid to study of the effects of rain fed culture on quality of medicinal plants. In order to investigate the establishment, growth and yield of some of perennial medicinal plants (Thymus caramanicus, Elaeagnus angustifolia, Olea europaeain, Thymus vulgaris, Rosa damascena, Thymus daenensis, Artemisia persica, Ferula assa feotida, Glycyrrhiza glabra, Rosmarinus officinalis, Lavandula officinalis, Salvia officinalis, Achillea millefolium ), the study was conducted using a randomized complete block design (RCBD) with 3 repli cations during 3 years from 2012 to 2014 in the Kohpanj mountains in the west of Bardsir city. During the growing seasons, the phonological and morphological events were recorded and finally analyzed by SAS software and the means were compared using Dunca n's Multiple Range Test at 0.05 level. The results showed Thymus caramanicus, Elaeagnus angustifolia and Olea europaeain destroyed in the first summer because of environmental drought. Thymus vulgaris, Rosmarinus officinalis, lavandula officinalis, Achille a millefolium and Salvia officinalis Survived in the first year, but destroyed in the second year. Rosa damascena 85%), Thymus daenensis (60%), Artemisia persica (77%), Ferula assa feotida (100%) and Glycyrrhiza glabra (100%) had the most survival rate am ong the species. With aging, dry weight of the plants were increased. The greatest dry weights were in Thymus daenensis, Artemisia persica and Ferula assa feotida respectively equal 188, 135.6 and 16 g/m 2 . The greatest dry weight of root in Glycyrrhiza gl abra (173.3 g/m 2) obtaind in the third year. The most number of flowers in Rosa damascena (31 flowers per plant) obtained in the third year.

Numerous soil erosion models are developed and are applied in soil erosion studies as an acceptable feature in order overcome problem of lack of the adequate data on soil erosion and sediment yield. The Universal Soil Loss Equation (USLE) is one of the primitive empirical models in estimation of erosion that is used continuously. In this study, the accuracy of USLE model and some of its versions including MUSLE-E, MUSLE-S and AOF are evaluated in event-based in North Khorasan semi-arid regions. For this goal, the sediment due to 20 rainfall event is measured in experimental plots in Sanganeh soil conservation research Institute of Mashhad as a definitive of semi-arid rangelands of Khorasan. Then the erosion amount due to each rainfall event is estimated using selected various versions of USLE. Results obtained from application of each model compared with measured sediment values of selected plots and finally the accuracy and efficiency of mentioned models are evaluated. The obtained results of evaluation from 20 meters plots show a statistical relation and significant correlation between estimated amounts of MUSLE-E and MUSLE-S models and observed sediment. According to non-significant difference between models results and observation amounts of sediment (tMUSLE-E=1.53 and tMUSLE-S=1.63) and also lower statistics of RRMSE, efficiency of these two models in estimating erosion amount is also greater than the others. The USLE and AOF models cannot appropriately estimate observed sediment because they are not in good agreement.