فهرست مطالب

Desert
Volume:19 Issue: 1, Winter - Spring 2014

  • تاریخ انتشار: 1393/05/10
  • تعداد عناوین: 10
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  • Mohammadali Zare Chahouki, Asghar Zare Chahouki, Arash Malekian, Reza Bagheri Fahraji, S.A. Vesali Pages 1-9
    Rainfall is considered a highly valuable climatologic resource, particularly in arid regions. As one of the primary inputs that drive watershed dynamics, rainfall has been shown to be crucial for accurate distributed hydrologic modeling. Precipitation is known only at certain locations; interpolation procedures are needed to predict this variable in other regions. In this study, the ordinary cokriging (OCK) and collocated cokriging (CCK) methods of interpolation were applied for rainfall depths as the primary variate associated with elevation and surface elevation values as the secondary variate. The different techniques were applied to monthly and annual precipitation data measured at 37 meteorological stations in the Central Kavir basin. These sequential steps were repeated for the mean monthly rainfall of all twelve months and annual data to generate rainfall prediction maps over the study region. After carrying out cross-validation, the smallest prediction errors were obtained for the two multivariate geostatistical algorithms. The cross-validation error statistics of OCK and CCK presented in terms of root mean square error (RMSE) and average error (AE) were within the acceptable limits for most months. Then the two approaches were compared to select of the most accurate method (AE close to zero and RMSE from 0.53 to 1.46 for 37 rain gauge locations for all months). The exploratory data analysis, variogram model fitting, and generation precipitation prediction map were accomplished through use of ArcGIS software.
    Keywords: Altitude, Central Kavir basin, Cokriging, geographical information system, Precipitation
  • Tayyebeh Mesbahzadeh, Hasan Ahmadi Pages 11-15
    Wind regime data from the Jask meteorological station from a 20-year statistical period 1985-2005) was analyzed using the Fryberger method to investigate sand drift potential (DP) in this area. The resultant drift potential and directional variability of wind were calculated and illustrated. Average annual sand DP was estimated to be 460 vector units (VU), and the sand flux is 51 m3/m.year. Therefore, in view of the wind’s erosive power (calculated by software using the Lettau-Lettau equation) and according to Fryberger’s classification 1979), this area is categorized as a high energy wind environment. Calculating DPt in different seasons showed that the strongest winds blow in summer and winter (158.8 and 152.4 VU), and autumn had the lowest DP. In summer, the wind blows in a southsoutheast pattern which differs from that of other seasons. Autumn also has the highest frequency of winds swifter than threshold velocity. The unidirectional index (RDP/DPt) value is 0.08 for this region, which causes the formation of transverse dunes (barkhanoid) from south-southeast to north-northwest.
    Keywords: Wide regime, Sand drifts potential, Fryberger method
  • Yadollah Yousefi, Jafar Masoompour Samakosh Pages 17-25
    The variability of temperature and precipitation is regarded as one of the main characteristics of the climate. Precipitation and its results, especially results such as droughts, vary on different temporal and spatial scales. The purpose of this paper is to determine the frequency of the inter-annual variability of the driest month in north-west Iran. In order to obtain the best results, we used 11 synoptic weather stations and included 30 years of continuous data records (1977-2006). Initially, the driest months were determined using the Standardized Precipitation Index (SPI); thereafter, the harmonic method was applied for closer examination and demonstration of the frequency of precipitation. The results derived from the harmonic method showed that the highest percentage of variance distribution (approximately 80%) is found in the central sections of the region according to the first harmonic of the Zanjan station. In these sections, the inter-annual changes of in the driest months typically fit a semi-annual pattern during the examined period. In the northern parts, higher harmonics are required to explain variance, which implies a higher variability and a lack of consistency in the occurrence of the driest month in these regions. The lowest PVR1 value (nearly 28%) was registered by the Ardebil station. Therefore, in Zanjan station, the inter-annual changes of the examined component have more homogeneity owing to the high PVR value of the first harmonic, while the level of variability in the driest months was higher in stations like Ardebil. Higher harmonics are required to explain this variance.
    Keywords: Variability, Harmonic, Drought, Variance, North, West of Iran
  • Hamid Abbasdokht, Ahmad Gholami, H. Asghari Pages 26-33
    To study the effects of halopriming and hydropriming in overcoming salt and drought stress in corn (Zea mays L.), two experiments were separately conducted at Shahrood University of Technology. Seed treatments consisted of control (untreated seeds), soaking in distilled water for 32 h (hydropriming), and soaking in 50 mmol solution of CaCl2 for 16 h (halopriming). Germination and early seedling growth were studied using distilled water (control) and osmotic potentials of -0.4, -0.8, and -1.2 MPa from NaCl (salinity stress) and polyethylene glycol [PEG 6000 (drought stress)]. Results showed that in both salinity and drought experiments, germination percentage reduced significantly according to decreased osmotic potential. Hydroprimed and haloprimed seeds achieved the minimum reductions in germination percentage. The maximum reduction in germination percentage was recorded from untreated seeds (control). Minimum reduction percentages of root length (RPL root) and shoot length (RPL shoot) were attained from hydroprimed and haloprimed seeds due to NaCl and PEG conditions (0.4 MPa), and maximum RPL root and RPL shoot were attained from controlled seeds due to NaCl and PEG (-1.2 MPa) conditions. The reduction percentage of dry weight for root (RPD root) and shoot (RPD shoot) increased according to increased osmotic potential in both NaCl and PEG, but RPD for shoot was significantly affected compared with RPD for root. Interaction of seed priming treatment and osmotic potential for the germination index (GI) showed that under 0 and - 0.4 MPa, hydroprimed and haloprimed seeds had higher GI as compared with untreated seeds due to NaCl and PEG conditions. Interaction between the seed priming treatment and osmotic potential significantly affected the vigour index (VI) due to NaCl and PEG conditions, and halopriming significantly increased VI at high osmotic potentials. On average, the VI of haloprimed seeds was higher than that of untreated seeds at high osmotic potentials and was not significantly different from hydroprimed and untreated seeds at low osmotic potentials. It is concluded that under salinity stress, the osmotic effect is more important than the toxic effect in loss of seed germination. Moreover, hydropriming practically ensured rapid and uniform germination with few abnormal seedlings.
    Keywords: Seed establishment, Germination indices, Seedling growth
  • Reza Erfanzadeh, Sayed Hamzeh Hosseini Kahnuj, Julien Petillon Pages 35-43
    In order to estimate the relationship between forage quality and preference value of plant species for Raini goats (Capra aegagrus hircus), a field study was carried out on Raini goats’ grazing behavior in some desert habitats. Crude protein (as the most important factor affecting forage quality) of all plant species was measured at two phenological stages (spring and summer, 2010) in the dry rangeland of Talkhabad, Iran. In addition, the preference value of plant species by free-ranging goats was estimated by visual estimation during the two seasons. One-way ANOVA and paired t-test revealed that forage quality and preference value by goats differed among plant species and between seasons. There was no significant relationship between forage quality and preference value (linear regression and Pearson correlation). Only a few plant species had both high quality and high preference (e.g., Taverniera cuneifolia). An interesting outcome was the importance of minor low-quality feeds such as Ziziphus spina-christ fruit in the goats’ diet. Raini goats were also highly selective feeders, changing their diet from grazing to browsing and vice versa, which highlights the importance of diversified botanical structures and the preservation of shrubs and trees in their desert habitats.
    Keywords: Dry rangeland, Forage quality, Raini goat, Plant phenological stage, Preference value
  • Hassan Khosravi, Gholamreza Zehtabian, Hassan Ahmadi, Hossein Azarnivand Pages 45-55
    Desertification in arid, semi-arid and dry sub-humid regions is a global environmental problem. Considering the increasing importance of desertification and its complexity, the necessity of giving attention to desertification criteria and indices is essential. Models and methods such as MEDALUS, UNEP-FAO, and others have been proposed on local and national scales. In this research, IMDPA was selected from among different existing methods, and desertification intensity was evaluated on the basis of two criteria, soil and water, and 13 indices: soil depth, electrical conductivity of soil, texture, gravel percentage, drainage, sodium absorption ratio, type of geologic formation, slope, groundwater table fluctuation, electrical conductivity of water, color concentration, water crisis index, and water shortage for livestock and wildlife. Each criterion was assessed based on the selected indices which resulted in the qualitative mapping of each criterion based on the geometric average of the indices. Finally, a sensitive map of the region was extracted using the geometric average of all criteria. Thematic databases with a 1:50000 scale resolution were integrated and elaborated in a GIS based on ILWIS and arcGIS. Analysis of desertification criteria in the Kashan region showed that, among the studied criteria, water criterion is a major problem in the study area. It has a geometric average of 3.59 which shows very high class, while soil criterion with a weighted average of 2.12 stands in the medium class of desertification. The results also showed that groundwater decrease and water crisis index with a quantitative value of 3.72 classified in a very high class of degradation and depth with quantitative value of 1.20 classified in a low class of desertification were the most and least effective factors, respectively, among the studied indices on land degradation.
    Keywords: Land Degradation, IMDPA Model, Index, Criteria, Kashan
  • Samira Hossein Jafari, Mohammad Reza Tatian, Reza Tamartash, Ali Akbar Karimian Pages 57-63
    Owing to the importance and necessity of identifying soil properties in arid rangeland management, and the variable effects of different kinds of herbivores on soil, this study compares some of the physical and chemical properties of soil between two regions experiencing livestock and wildlife grazing in the desert rangelands of Kalmand-Bahadoran in Yazd province. The key areas in two regions experiencing livestock and wildlife grazing were selected, and soil samples were taken at depths of 0-30 cm using the systematic random sampling method. All samples were then transferred to the laboratory to determine the desired parameters. Finally, soil characteristics were compared between the two regions. The results indicate that physical properties of the soil such as clay and moisture percentage show no significant differences. Bulk density in the region of livestock grazing reveals a highly significant increase compared to the area under wildlife grazing (P<0.01). Calcium carbonate, acidity and electrical conductivity parameters also saw a significant increase from 18.33%, 8.47% and 1.46% in the region with livestock grazing to 14.91%, 8.36% and 1.35% on the wildlife grazing site respectively (P<0.01). In terms of organic matters there was no significant difference between the two study sites. Overall, changes in soil properties have occurred as a result of wildlife grazing from halophyte and shrub species and from less grazing pressure at the site.
    Keywords: Desert, Livestock, Wildlife, Physical Chemical Properties, Soil, Yazd
  • Mahdieh Ebrahimi Pages 65-73
    In this research a pot experiment was carried out to investigate the remediation ability of E. camaldulensis Dehnh in Lead-Zinc (Pb-Zn) contaminated soil. The study also investigated the effects of ethylenediaminetetraacetic acid (EDTA) and diethylenetrinitrilopentaacetic acid (DTPA) on the phytoremediation efficiency of the plant species, and harvest time as a suitable dose of chelating agents was considered. When the plants had grown for 30 days, the seedlings were harvested to determine the concentration of metals in plant tissues and soil. In general, Pb level decreased in the order of: shoot > soil > root, whilst Zn content decreased in the sequence shoot > root > soil. As a second step, contaminated soils were treated with EDTA (1.5, 3, 6, 9mmolkg-1) and DTPA (1.5, 3, 6, 9mmolkg-1). The results demonstrated that chelating agents enhance metal content in E. camaldulensis. The greatest bioconcentration factor in EDTA treatments (3.94) was observed in 9EDTA treatment followed by 6EDTA treatment (3.41). Similarly this was observed for 9DTPA (2.30) and 6DTPA (2.23) respectively. With respect to non-significant difference between 9EDTA and 6EDTA treatments and between 6DTPA and 9DTPA, low doses (6mmolkg-1) were used in the third step for the highest heavy metal uptake over 30, 60 and 90 days. Results reveal that the concentration of metal soil solution decreases gradually with the passage of time. The results indicate that E. camaldulensis has the potential for the phytoextraction of metal-contaminated soils but should not be used unless the biomass containing such accumulated metals is removed for disposal. Significant improvement over current chelate-assisted phytoextraction of metals may be possible but should be implemented cautiously because of the environmental risks.
    Keywords: Phytoextraction, Environmental Pollution, Lead, Zinc, Chelating Agents
  • Nozar Ghahreman, Mahsa Sameti Pages 75-81
    Evaporation is a fundamental parameter in the hydrological cycle. This study examines the performance of M5 model tree and artificial neural network (ANN) models in estimating potential evapotranspiration calculated by Penman- Monteith and Hargreaves- Samani equations. Daily weather data from two meteorological stations in a semi-arid climate of Iran, namely Kerman and Zahedan, were collected during 1995-2004 and included the mean, maximum and minimum air temperatures, dewpoint, relative humidity, sunshine hours, and wind speed. Results for both stations showed that the performance of the M5 model tree was more accurate (R=0.982 and 0.98 for Penman-Monteith equation and R=0.983 and 0.98 for Hargreaves-Samani equation in Kerman and Zahedan, respectively) than the ANN model (R=0.975 and 0.978 for Penman-Monteith equation and R=0.967 and 0.974 for Hargreaves-Samani equation in Kerman and Zahedan, respectively), but the models’ differences were insignificant at a confidence level of 95%. It also performed better at the Zahedan station using the Penman- Monteith equation. The most significant variables affecting the potential evapotranspiration in the case of the Penman–Monteith equation were found to be mean air temperature, sunshine hours, wind speed, and relative humidity. Similarly, for the Hargreaves-Samani equation, the maximum and minimum temperatures, sunshine hours, and wind speed were determined to be the most significant variables. Further studies in other climates are recommended for further analysis.
    Keywords: ANN, Machine learning, Penman, Monteith, Hargreaves, Samani
  • Zohreh Kheradpisheh, Seyed Ali Almodaresi, Yasamin Khaksar, Lida Rafati Pages 83-90
    Groundwater quality management is one of the most important issues in many arid and semi-arid regions, including Iran. Nitrate (NO3 -) is one of the most common anions contaminating groundwater. This study aimed to range nitrate concentrations in water resources in Bahabad plain in Yazd province. To evaluate the nitrate data in this descriptive study, 260 nitrate samples from 13 wells in Bahabad were assessed from 2003 to 2013. The two interpolation techniques of kriging and inverse distance weighting (IDW) were used to obtain the spatial distribution of groundwater quality parameters by means of Arcview GIS 10 software. The results of this study showed that the kriging method is more accurate than IDW for groundwater quality mapping, based on the lower root mean square error (RMSE) of kriging. Nitrate levels in samples from regional wells were lower than standard levels for Iran and the world. However, nitrate contamination tended to increase from 2003 to 2013. Furthermore, the greatest nitrate contamination was found in the southern part of Bahabad. In conclusion, kriging seems to be an appropriate method for estimating nitrate levels in groundwater in Bahabad. We recommend action be taken in order to stop the increasing trend of groundwater nitrate contamination in this area.
    Keywords: Groundwater, Nitrate, Kriging, IDW, Bahabad plain