Mahbobe Hajibigloo; Mohammadtaghi Dastorani; Abbas Ali Ghezelsofloo; Mohammad Reza Ekhtesasi
Abstract
The morphology of a river system is affected by dominant watershed processes includingclimatic, hydrologic, hydraulic, erosion and sedimentation, geological and topographicalcharacteristics of the river environment and watershed. Understanding the interaction betweenthe river form and dominant watershed ...
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The morphology of a river system is affected by dominant watershed processes includingclimatic, hydrologic, hydraulic, erosion and sedimentation, geological and topographicalcharacteristics of the river environment and watershed. Understanding the interaction betweenthe river form and dominant watershed processes in river systems is necessary for recognitionof river behavior and of importance for developing river environments conceptual models.In this research the aim was to evaluate morphological characteristics caused by dominantwatershed processes in the Firoozeh-shahjoob river of north Khorasan and extract equations inorder to mathematically link between the river physical features and watershed processes. Forthis purpose, the HEC-RAS hydraulic model after doing sensitivity analysis and calibrationprocess was used to simulate the relation between dominant watershed processes and riverphysical factors for 37 reaches of this river. Considering the standard error, level of confidenceand coefficient of determination, compared to simple linear models, second order (quadratic)and third order (cubic) models, exponential models were the most suitable ones to extract themathematical relation between geometrical characteristics and the related dominant processesin this river system.
Mina Bashmaghi; Reza Erfanzadeh; Mahdi Abedi
Abstract
In the current study, the variation of soil seed bank density was evaluated in two different fire severities, i.e. low and high. Soil sampling was done in Sharlegh site, Golestan national park. Therefore, 5 soil samples for both grass patches and shrub patches in each burnt and control sites were selected. ...
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In the current study, the variation of soil seed bank density was evaluated in two different fire severities, i.e. low and high. Soil sampling was done in Sharlegh site, Golestan national park. Therefore, 5 soil samples for both grass patches and shrub patches in each burnt and control sites were selected. In burnt sites, grass and shrub patches were considered as low and high fire severities, respectively. For data analysis, GLMM and T test were applied.The seed germination method was used in green house to identify soil seeds. Altough, the results of statistical R software indicated that avrage soil seed bank density in burnt-site (74.5) had no significant difference compared with unburnt-site (132.3); however, fire had significant effect on plant functional groups. The results showed that soil seed bank density of different plant functional groups were affected differently by fire severities,. Total seedlings of annual forb was increased (1785 to 3543)and decreased (5000 to 1471) in low and high fire severities, respectively. Total seedlings of pernnial grasses were significantly decreased (7114 to 842.9) in low fire severity while high fire severity had no significant effect on perennial grasses seed bank density. Fire severity had no significant influence on soil seed bank richness. Our results indicated that the surface and severity of fire should be included and interpreted in the future studies.
Mohammad Ali Zare Chahouki; Lyla Khalsi Ahvazi; Hossein Azarnivand
Abstract
The aim of this study was providing plant species predictive habitat models by using logisticregression method. For this purpose, study area conducted in north east rangelands of Semnanmodeling vegetation data in addition to site condition in formation including topography, and soil wasprepared. sampling ...
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The aim of this study was providing plant species predictive habitat models by using logisticregression method. For this purpose, study area conducted in north east rangelands of Semnanmodeling vegetation data in addition to site condition in formation including topography, and soil wasprepared. sampling was done within each unit of sampling parallel transects and 1 vertical transectwith 750m length, each containing 15 quadrates (according to vegetation variations) were established.Quadrate size was determined for each vegetation type using the minimal area method. Soil sampleswere taken from 0-20 cm and 20-80 cm in starting and ending points of each transect. Logesticregression (LR) techniques were implemented for plant species predictive modeling. To plantpredictive mapping, it is necessary to prepare the maps of all affective factors of models. To mappingsoil characteristics, geostatistical method was used based on obtained predictive models for eachspecies (through LR method). The accuracy of the predicted maps was tested with actual vegetationmaps. In this study, the adequacy of vegetation type mapping was evaluated using kappa statistics.Predictive maps of Astragalus spp. ( κ =0.86), Halocnemum strobilaceum ( κ =0.51), Zygophylumeurypterum ( κ =0.58) and Seidlitzia rosmarrinus ( κ =0.6) with narrow amplitude is as the same ofactual vegetation map prepared for the study area. Predictive model of Artemisia sieberi ( κ =0.33),due to its ability to grow in most parts of north east rangeland of Semnan with relatively differenthabitat condition, is not possible.
Maryam Asadi; Ali Fathzadeh
Abstract
Understanding of suspended sediment rate is one of the fundamental problems in water projects which water engineers consistently have involved with it. Wrong estimations in sediment transport cause incorrect design and destruction of hydraulic systems. Due to the difficulty of suspended sediment measurements, ...
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Understanding of suspended sediment rate is one of the fundamental problems in water projects which water engineers consistently have involved with it. Wrong estimations in sediment transport cause incorrect design and destruction of hydraulic systems. Due to the difficulty of suspended sediment measurements, sediment rating curves is considered as the most common method for estimating the suspended sediment load. The main purpose of this research is the capability challenge of this method in comparison to some state of the art models. In this study, we selected some computational intelligence models (i.e. K-nearest neighbor (KNN), artificial neural networks (ANN), Gaussian processes (GP), decision trees of M5, support vector machine (SVM) and evolutionary support vector machine (ESVM)) and compared them with their sediment rating model in 8 basins located in Gilan province. Daily sediment and discharge data considered as the input data for 30-years. Evaluation of the results indicated that the Gaussian process model has the lowest residual sum of squares (RMSE) and the highest correlation coefficient (r) than the other models.
Bahareh Jebalbarezi; Gholamreza Zehtabian; ِAli Tavili; Hassan Khosravi
Abstract
Investigation of the effect of plant community on limited water resources of deserts is an important issue in water resources management. Different species of Haloxylon are compatible with desert condition and can use groundwater resources due to deep roots and proper structural condition. The purpose ...
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Investigation of the effect of plant community on limited water resources of deserts is an important issue in water resources management. Different species of Haloxylon are compatible with desert condition and can use groundwater resources due to deep roots and proper structural condition. The purpose of this study was investigation of the effect of Haloxylon planted forests on groundwater resources in Jafarieh plain. For doing the study, at first the number of Haloxylon plants was determined in these forests using satellite images and JMicroVision software. Then using minimum water requirement of each plant, estimated with lysimeter, the number of surplus plants was determined based on their water requirement and rainfall of the region. Then groundwater level status was determined using GMS 8.3 software and MODFLOW model. The results showed that the number of Haloxylon plants in the study area was equal to 3746291 and the amount of groundwater evacuation by these plants was equal to 56.194 Mm3. The reduction of groundwater table was about 0.46 meter in the first study period (1992-2001) and 0.93 meter in the second study period (2002-2012) so that the reduction of groundwater level in the second study period was about 2 times bigger than the first study. This results showed that severe reduction of groundwater table has happened in recent decade because of planting Haloxylon. However the positive effects of these forests on reducing damages of dust storms should not be ignored.
Saeedeh Khaghani; Hossein Azarnivand; Mohammad Jafari; Abdollah Mollafilabi; Ali tavili
Abstract
This experiment was conducted as a split-plot factorial based on a randomized complete block design with three replications in the medicinal plants' farm of Islamic Azad University in 2017. In this experiment, water stress was considered as the main factor in four levels of irrigation including 100%, ...
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This experiment was conducted as a split-plot factorial based on a randomized complete block design with three replications in the medicinal plants' farm of Islamic Azad University in 2017. In this experiment, water stress was considered as the main factor in four levels of irrigation including 100%, 75%, 50% and 25% of the plant water requirement in the main plots. In addition, the application of different levels of zeolite (including no application of zeolite, two, four, six tons per hectare), as well as application of salicylic acid at two levels (0.5 and 1 mM) were considered as secondary factors in the form of factorial on subsidiary plots. The results showed that the effect of different levels of water stress on the traits such as plant height, number of lateral branches, plant wet weight, leaf area index, number of flowers in inflorescence was significant at 1% and on plant dry weight was significant at 5%. Salicylic acid application was also significant on some traits such as flower number in inflorescence, leaf area and dry weight at the probability level of 1%, and on plant volume and wet weight at 5% level. In addition, the effect of different levels of zeolite application was significant on plant height, number of lateral branches, wet weight, dry weight, leaf area index, number of flower in inflorescence at 1% level.
S.M Heshmatol Vaezin; S Ghanbari; ALI Tavili
Volume 63, Issue 2 , September 2010, , Pages 183-14
Abstract
Eremurus and forage are main by-products in the Khazangah rangelands of Makoo region. Eremurus is harvested and used by local people in a period of 30 days during the spring in this region. At this study, Eremurus and forage have been evaluated financially and the data were obtained through field work ...
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Eremurus and forage are main by-products in the Khazangah rangelands of Makoo region. Eremurus is harvested and used by local people in a period of 30 days during the spring in this region. At this study, Eremurus and forage have been evaluated financially and the data were obtained through field work using unstructured interviews as well as direct observation. The harvested Eremurus value was estimated based on harvest costs and by means of market price. The data were analyzed through financial evaluation, annual present net value and infinite present net value or expected value. The results showed that gross revenue, economical rent and economical benefit per household were 4564 and 348 thousand Rials/yr, respectively. The amount of net benefit through harvested Eremurus was also 16748 thousand Rials/ha/yr. The Rangeland Expectation Value per hectare was estimated 670 thousand Rials/yr and 10.5 million Rials/yr from Eremurus and feed, respectively. Total Rangeland Expectation Value per hectare was estimated 11.17 Thousand Rials while the ratio of Rangeland Expectation Value of Eremurus to Total Rangeland Expectation Value was computed 6 percent. The rangelands of this region have much more products. Among them forage and Eremurus have been considered at this study. These products play a main role in local economy of the region.
M. Jafari; A. Tavili; M. Rostampour; M. A. Zare Chahouki; J. Farzadmehr
Volume 62, Issue 2 , October 2009, , Pages 197-211
Abstract
This study was carried out to investigate the effective environmental factors in the distribution of vegetation in Zirkouh rangelands of Qaen. After delimitation of the study area, sampling of soil and vegetation were performed using randomized- systematic method. Vegetation cover was recorded by using ...
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This study was carried out to investigate the effective environmental factors in the distribution of vegetation in Zirkouh rangelands of Qaen. After delimitation of the study area, sampling of soil and vegetation were performed using randomized- systematic method. Vegetation cover was recorded by using Braun-Blanquet combined abundance-cover scale in each sample. Within each sample, one profile was dug and soil samples being taken at 0-20 cm and 20-100 cm depths. Physical-chemical characteristics were determined include texture, lime, organic matter, soil moisture content, saturation moisture, EC and pH. Five vegetation groups were identified after the application of TWINSPAN method and were named after the characterizing species as follows: Salsola richteri-Aelorupes littoralis; Zygophyllum eurypterum-Haloxylon ammodendron; Artemisia sieberi-Zygophyllum eurypterum; Ammodendron persicum-Stipagrostis pennata; Artemisia aucheri-Amygdalus scoparia. The results of PCA showed that environmental factors best related with the distribution of this vegetation are texture, lime, organic matter, soil moisture content, saturation moisture, elevation and slope.
Pejman Tahmasebi; Ataollah Ebrahimi; Nabiollah Yarali
Abstract
هنگاهی میتوان قضاوت درستی در ارزیابی پوشش گیاهی مرتع داشت که طرح آماربرداری انتخاب شده باشد. از اینرو تعیین یک اندازه و شکل قطعه مناسب که بتواند دقت و صحت مناسبی در ...
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هنگاهی میتوان قضاوت درستی در ارزیابی پوشش گیاهی مرتع داشت که طرح آماربرداری انتخاب شده باشد. از اینرو تعیین یک اندازه و شکل قطعه مناسب که بتواند دقت و صحت مناسبی در برآورد متغیرهای مرتعی پوشش داشته باشد موجب افزایش کارآیی نمونهبرداری میشود. در این مطالعه با لحاظ کردن چندین معیار شامل دقت، زمان، نسبت محیط به مساحت و راحتی و قابل استفاده بودن به دنبال تعیین قطعهی خواهیم بود که برآورد قابل قبولی از چندین متغیر شامل درصد پوشش فرمهای رویشی مختلف، سنگ و سنگریزه، درصد لاشبرگ و خاک لخت داشته باشد. برای این منظور با استقرار قطعههای با اندازه و شکلهای مختلف شامل1×1، 1×2، 4/1×4/1، 4×5/0، 2× 2 و4×4 متری درصد پوشش شکل های مختلف رویشی و زمان نمونهبرداری اندازهگیری در آنها شد. برای انتخاب بهترین قطعه از بین گزینههای فوق از روش تصمیمگیری سلسلهمراتبی استفاده شد. همچنین با استقرار 5 قطعه آشیانهای (تودرتو) با ابعادcm 25*25 متر تاm 16*16 و تعیین قطعههای حداقل، کارآیی این روش با قطعههای فوق که چندین معیار را همزمان در خود لحاظ میکند مورد مقایسه قرارگرفت. نتایج کلی نشان میدهد که دقت برآورد متغیرهای مختلف با افزایش سطح افزایش مییابد. با اینوجود افزایش دقت برآورد متغیرهای مختلف با افزایش سطح در قطعههای کوچکتر بسیار چشمگیر بوده و با رسیدن به قطعه 4 متر مربعی تقریباً به سطح ثابتی رسید. نتایج حاصل از تحلیل سلسله مراتبی نشان داد که با در نظر گرفتن معیارهای دقت، زمان، نسبت محیط به مساحت و راحتی و قابل استفاده بودن، قطعه 4 متر مربعی بهترین گرینه انتخابی برای تخمین متغیرهای پوشش گیاهی است. قطعههای آشیانهای مستقر شده قطعه حداقلی با مساحت بزرگتر از 32 متر مربع را تعیین کردهاند. نتایج حاصل از این پژوهش موید این موضوع است که 1) در مراتع نیمه استپی برای برآورد متغیرهای پوشش گیاهی قطعه 4 متر مربعی بهترین است
2) قطعههای حداقلی که در روش آشیانهای تعیین میشوند نمی تواند در مناطقی که پوشش گیاهی ناهمگنی زیادی دارد بهترین قطعهها برای برآورد چندین متغیر پوشش گیاهی باشد 3) بهترین برآورد از متغیرهای بررسی شده در دو برابر حداکثر تاج پوشش گونههای موجود در منطقه مشاهده نشده است و روش استفاده از دو برابر بودن بودن اندازه قطعه از تاج پوشش حداکثر گونهها برای اندازه قطعه در این مناطق صحیح نیست 4) برای انتخاب بهترین قطعه، محقق باید با لحاظ کردن چندین معیار تصمیمگیری از بین قطعههای مورد نظر، یکی را که بیشترین کارایی را در برآورد متغیرهای پوشش دارد انتخاب کند.
Ataollah Kavian; Feryal Hayavi; Mehdi Boroghani
Abstract
Splash erosion recognized as first stage of erosion process that results of bombing soil surface with rain drop. Falling rain drops to soil surface resulted moving soil particles and destructing soil structure. At this research effects of various PAM rate (0, 2, 4 and 6 kg.ha) on splash erosion on three ...
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Splash erosion recognized as first stage of erosion process that results of bombing soil surface with rain drop. Falling rain drops to soil surface resulted moving soil particles and destructing soil structure. At this research effects of various PAM rate (0, 2, 4 and 6 kg.ha) on splash erosion on three soil textuere clay, silty clay and sandy clay loam was tested. Simulations were done with rain intensity of 95 mm/h using a FEL3 rainfall simulator in laboratory. Splash erosion rate were measured using splash cup. Results showed that there is no statistically difference between different soil textures in order to decreasing splash rates. Effect of different applying PAM in splash erosion rate showed that there is significantly differences between control treatment with 4 and 6 Kg/ha treatment in 95% level (Fvalue=4.5, Pvalue= 0.039) in sandy clay loam soil texture. Also the results showed splash erosion rates have decreased by 42.3 and 52 percent comparing to control treatment when applied 4 and 6 Kg/ha treatments. Our findings can be useful for better management of agricultural soils in order to sustainable yield and soil sonservation.
Ruollah Taghizadeh Mehrjardi; Fereydoon Sarmadian; Gholem Reza Savaghebi; Mahmoud Omid; Nourayer Toomanian; Mohammad Javad Rousta; Mohammad Hasan Rahimiyan
Abstract
In recent years, alternative methods have been used for estimation of soil salinity. Therefore, at present research, 600 soil samples collected from Ardakan in central Iran. Then EM38 and terrain parameters such as wetness index, land index and curvature as readily measured properties and soil salinity ...
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In recent years, alternative methods have been used for estimation of soil salinity. Therefore, at present research, 600 soil samples collected from Ardakan in central Iran. Then EM38 and terrain parameters such as wetness index, land index and curvature as readily measured properties and soil salinity (0-30 and 0-100) as predicted variables were measured. After that, the data set was divided into two subsets for calibration (80%) and testing (20%) of the models. For predicting of mentioned parameters, ANFIS, GA, ANNs and MLR were applied. In order to evaluate models, some evaluation parameters such as root mean square, average error, average standard error and coefficient of determination were used. Results showed that the ANFIS model gives better estimation than the other techniques for all characteristics whereas this model increased accuracy of predictions about 17 and 11% for EC30 and EC100 respectability. After ANFIS model, GA and ANN had better accuracy than multivariate regression.
Marziyeh Haji Mohammadi; Aliakbar Nazari Samani; Arash Zare Garizi; Hamidreza Keshtkar; Mahmood Arabkhedri; Amir Sadoddin
Abstract
The SWAT model is widely used to simulate watersheds and evaluate the impact of conservation watershed management practices. In this model, the simulation of the watershed processes is based on hydrological response units (HRUs) which are created by overlaying land use /land cover, soil and slope maps. ...
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The SWAT model is widely used to simulate watersheds and evaluate the impact of conservation watershed management practices. In this model, the simulation of the watershed processes is based on hydrological response units (HRUs) which are created by overlaying land use /land cover, soil and slope maps. Meanwhile, in the HRUs definition steps, these units become conceptual and lose their spatial location and continuously. This approach is a useful and often inevitable way to simulate large and heterogeneous watersheds in terms of computational efficiency. However, if the aim is spatializing and evaluating the effectiveness of management methods on runoff, sediment and other pollutants in medium to small basins, it is necessary to know the exact location of HRUs. The purpose of conducting this study was present a new approach to defining spatial and independent HRUs and compare the simulation results based on this method with the standard form of the model. In the new approach, independent and spatial HRUs are defined through pre-processing procedures in GIS and uniquely named soil units. The model results of both approaches were very similar and no significant difference was observed in the model outputs in Taleghan watershed. The Nash-Sutcliffe coefficient of the simulated runoff and sediment at the outlet with the standard approach was 0.75 and 0.64, respectively. While, it was obtained 0.74 and 0.61, respectively for the new approach. The definition of spatial HRUs by applying the proposed method provides more tangible and practical outputs, which is more beneficial for identifying the critical areas as well as locating conservation practices compared to the conceptual HRUs approach.
Afshin Jahanshahi; Alireza Moghaddamnia; Hasan Khosravi
Abstract
To assessment and preparation of desertification mapping, much research has been conducted ever within and outside the country that has led to numerous regional models. To provide a regional model and quantitative assessment of current state of desertification, ShahrBabak plain with an area of 4112 square ...
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To assessment and preparation of desertification mapping, much research has been conducted ever within and outside the country that has led to numerous regional models. To provide a regional model and quantitative assessment of current state of desertification, ShahrBabak plain with an area of 4112 square kilometers (Km2) located in the Northwest of Kerman province were considered. In this study, to assess the severity of desertification using thirteen indices that five of them based on groundwater and include: electrical conductivity (EC), sodium absorption ratio (SAR), chloride (Cl), drop of groundwater and water table depth and three of them based on climate data and included: annual rainfall, Transeau drought index, drought index and also three of them based on vegetation and included: Conditions, exploitation and restoration of vegetation, water erosion and irrigation methods in format of desertification Iranian model IMDPA to investigation and determine the class of desertification intensity were done in each of work units. The final score of each of work units and then total area were determined using Geometric average from any of the mentioned indices. Finally the current status of desertification intensity classes were estimated in low, medium, high and very high classes. The results indicated that in the regional proposed model, the study area with respect to intensity of desertification is placed in about 61351 ha (14.92 %) in low class and about 138575 ha (33.7%) in medium class, about 117685 ha (28.62 %) in high class and about 93589 ha (22.76 %) in very high class. Also the weight average of quantitative value estimated 2.06 in total area that it indicated the medium desertification class in the total area.
Sadegh Abravesh; shirin mohamadkh; mohammadreza sarvati; manijeh ghohrodi
Abstract
Today, the dust problem has become a regional and global crisis. Dust and sandstorms can be considered as funding sources for the formation of sand dunes. The purpose of this study is to investigate the movement of dust production sources and their role in the formation of sand dunes in the Jalali sandy ...
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Today, the dust problem has become a regional and global crisis. Dust and sandstorms can be considered as funding sources for the formation of sand dunes. The purpose of this study is to investigate the movement of dust production sources and their role in the formation of sand dunes in the Jalali sandy area located in the east of Qom province. The research data includes library information, sampled points as well as information obtained from meteorological stations in Qom province and using the HYSPLIT model. The tools used in the research include climatic data from ArcGIS, WRPLOT, Google earth, Excel and NOAA satellite data. During the years (1987-2019), 89% of dust occurrence occurred in the warm half of the year and 11% in the cold half of the year. The drawn flowers of the three stations of Kuh-e-Sefid, Qom and Kushk-e-Nusrat show the superiority of the east, southeast, west and southwest directions towards Qom city. Dust also emphasizes dominance in the east in hot seasons. Routing and movement of dust in the sampled points at altitudes up to 1000 m and 1000 to 1500 m in reverse using the HYSPLIT model showed the external origin, deserts of Saudi Arabia, Syria and Iraq and the internal origin of the salt lake and plain Abandoned agricultural lands and lands have a more prominent role in the production of dust sources and the formation of glorious sand dunes.Keywords: Dust, Rose, HYSPLIT, WRPLOT, Jalali Sands.
Alireza Daneshi; mehdi vafakhah; Mostafa Panahi
Abstract
Due to problems of Urmia Lake, several strategies have been proposed by professionals to restore it. But it should be noted that the implementation of each plan and project within the watershed requires the participation ofstakeholders and farmers within that watershed. Due to the lack of attention to ...
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Due to problems of Urmia Lake, several strategies have been proposed by professionals to restore it. But it should be noted that the implementation of each plan and project within the watershed requires the participation ofstakeholders and farmers within that watershed. Due to the lack of attention to stakeholders, management of many natural resources and development projects has failed. Therefore, public acceptance and participation of stakeholders including those users who are engaged with farming and gardening was explored in some proposed approaches for restoring Urmia Lake. The study area was Siminehroud watershed as one of the largest Urmia Lake sub watersheds. Research instrument was a questionnaire which was filled by data obtained from interview with stakeholders and achieved results were analyzed using SPSS 17 software. The results showed that shift in irrigation system from traditional type to pressure irrigation system with 91.45% approval rating can be considered as the most successful strategy among poposed strategies. Compensation payment initiative specific to farmers for non-utilization of owned farming lands had the appropriate acceptance with 53.55%. Also 50.25% of stakeholders showed their inclination to the use of species of low water demands instead of those with high water demand providing that government support such scheme. Generally, it was revealed that increasing water charge anticipating subsequent reduction of water consumption will not be effective. Consequently, it can be stated firmly that irrigation system change must be put in executive priority and next priorities will be compensation payment to farmers and change in farming pattern.
Seyyed Morteza Abtahi
Abstract
The purpose of this study was to investigate vegetation dynamics and range conditions considering the climatic conditions and soil properties in Doolat Gharin in the South of Isfahan province of an area equal to 25 square kilometer. For this purpose, after determining vegetation types and associated ...
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The purpose of this study was to investigate vegetation dynamics and range conditions considering the climatic conditions and soil properties in Doolat Gharin in the South of Isfahan province of an area equal to 25 square kilometer. For this purpose, after determining vegetation types and associated species, the type of rangeland utilization, grazing season, the type of livestock and other relevant information, and vegetation data including canopy cover of annuals, perennial forbs, shrubs, total canopy cover, soil moisture and carbon were determined during four years. Data was collected along three transects in each vegetation types. For each transect 10 plots were established. The size of plots was 1 x 2 m, considering the life form of dominant species. Embrothermic diagram was drawn according to the monthly temperature and precipitation data of Semirom station. Data was analyzed of variance and means comparison were made using Duncan method. According to the results, significant differences were observed between years for canopy cover of annuals, shrubs, forbs, grass, soil cover and soil moisture and Bromus tomentellus (P<0.01) and total canopy cover, Poa bulbosa and soil organic carbon (P<0.05). In this site, the amount of vegetation and its variation are affected by precipitation changes.
Mehdi Teimouri; Ali Fathzadeh
Abstract
The discharge data used for hydrological modeling should be the long-term suitable random data without trend and jump which is followed a specific statistical distribution. In this study, the above mentioned conditions were evaluated for 31 years period (1974-2004) of annual mean discharge data of 10 ...
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The discharge data used for hydrological modeling should be the long-term suitable random data without trend and jump which is followed a specific statistical distribution. In this study, the above mentioned conditions were evaluated for 31 years period (1974-2004) of annual mean discharge data of 10 gauging stations of West Azarbaijan province. For this purpose, the non-parametric Spearman correlation coefficient as well as Mann-Kendall method, non-parametric Run-test, non-parametric without distribution test of CUSUM and Kolmogorov–Smirnov test were used to trend, jump, stochastic and distribution analysis of data, respectively. The results showed that data of all stations were stochastic with no jump and trend (except Pol-e-Bahramloo gauging station). Also, data of most of the stations followed the gamma probability distribution function
GH.A Heshmati; M S. Azimi; P Ashouri
Volume 63, Issue 3 , December 2010, , Pages 319-329
Abstract
Rangeland ecosystem contains various patches with different functions. Structural and functional characteristics of rangeland patches are changed by management practices and can be used to interpret management effects. The structural and functional characteristics of fertilized patches in two rangeland ...
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Rangeland ecosystem contains various patches with different functions. Structural and functional characteristics of rangeland patches are changed by management practices and can be used to interpret management effects. The structural and functional characteristics of fertilized patches in two rangeland ecosystems of Ghareh Ghir and Maraveh Tapeh were measured and analyzed in this study. A group of measurable and simple indices of landscape function analysis (LFA) methods were used to evaluate these characteristics. Five structural characteristics such as: the number of patches, total patch area, patch area index, landscape organization index and inter patch length mean on the east and western aspects of Ghareh Ghir and Maraveh Tapeh were measured. On the basis of statistical analysis, the structural characteristics of patches in the east and western aspects of the two areas (Ghareh Ghir and Maraveh Tapeh) were highly significant (P
Fatemeh bahreini; Fatemeh Panahi; Mohammad Jafari; Arash Malekian
Abstract
The complexity of drought phenomenon hinders our full understanding of its impact. Field sampling, Geographic Information Systems, SPI and NDVI, EVI and SAVI indices derived from 16-day interval MODIS images during 2000-2015 were used to better understand the effects of drought on vegetation In recent ...
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The complexity of drought phenomenon hinders our full understanding of its impact. Field sampling, Geographic Information Systems, SPI and NDVI, EVI and SAVI indices derived from 16-day interval MODIS images during 2000-2015 were used to better understand the effects of drought on vegetation In recent study, ground true map was prepared by sampling and field surveys and vegetation cover data was obtained from 32 sampling units in 320 plots over the entire study area. Then, the correlation between field sampling data and vegetation indices was estimated and vegetation cover models were produced for different indices. In this study, precipitation data of 14 stations within and around the study area were used and SPI was calculated at the same time scales with the vegetation indices to study the effect of drought on vegetation. The results showed that NDVI has had the highest correlation coefficient (R2=0.56) amongst the indices so it was selected for vegetation cover percentage mapping. Investigating NDVI rates and drought index in different temporal periods, 9-month SPI was found to have the best correlation with NDVI. On the basis of SPI analysis, it was found that the study area had the most severe drought in 2012 and the best wet condition in 2004. The similar trend was observed in NDVI. The comparison of classified images between 2004 and 2012 (with 42 % changes in poor vegetation) indicates the effect of drought on vegetation in the study area.
Sima Pourhashemi; mehdi boroghani; abolghasem Amirahmadi; MohamadAli Zanganeh Asadi; Mahdi Salhi
Abstract
Due to the drought and land use changes in recent years, dust storm phenomenon in Iran has increased. The purpose of this research is to identify and prioritize dust source areas using bivariate models (probability model of event weight and frequency ratio model) in R software environment and determine ...
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Due to the drought and land use changes in recent years, dust storm phenomenon in Iran has increased. The purpose of this research is to identify and prioritize dust source areas using bivariate models (probability model of event weight and frequency ratio model) in R software environment and determine the importance of each of the environmental factors affecting it in Khorasan Razavi province. To this porpuse, 65 dust extraction points were identified in the study area and a dust distribution map was prepared. Then maps of each of the factors influencing the occurrence of dust including soil maps, lithology, slope, vegetation index (NDVI), distance from the river, geomorphology and land use were prepared. Using the frequency and event weighting models, the weight of each effective factor and the relationship between each of the factors and the points of dust source were determined and, finally, priority maps of the dust source areas were prepared for the case study. Models were evaluated using the ROC curve. According to the results of both models, geomorphology units, land use and slope have the most effect on the occurrence of dust in the region, and both models have a frequency ratio and event weight with a sub-curve of 0.818 and 0.825, respectively. They accept.
Ghobad Rostamizad; Shahram Khalighi Sigaroodi; Mohammad Mahdavi
Abstract
Parameters as interception, infiltration, water storage on surface holes and soil profile, evapotranspiration are factors of loss water in a watershed and avoid from changing of precipitation to runoff. In this study, by use of HEC-HMS model and comparison of results of different methods of precipitation ...
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Parameters as interception, infiltration, water storage on surface holes and soil profile, evapotranspiration are factors of loss water in a watershed and avoid from changing of precipitation to runoff. In this study, by use of HEC-HMS model and comparison of results of different methods of precipitation loss evaluation (Initial and constant, Green & Ampt, SCS curve number, Deficit & Constant and Exponential loss) consider to various purpose function percent error in peak tried to classify the methods. In this way, based on every purpose function, the method with least percent difference of observed discharge to calculated discharge take place in first preference and other methods take place in next preferences. Result show that, Exponential loss method placed in first preference and it selected as optimum method for simulation of runoff and Green & Ampt, Initial and constant, SCS curve number, Deficit & Constant methods placed in next preferences respectively.
Hossein Arzani; javad Motamedi(torkan); Mahmood Hamidian; Zahra Arzani; Majid Akhshi
Abstract
To achieve the desired level of animal performance providing animal food supplies containing mineral elements is essential. For this purpose, mineral elements of 8 important rangeland species, including Ferula ovina, Prangus uloptera, Medicago sativa, Lotus goeblia, Trifolium montanum, Melilotus officinalis, ...
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To achieve the desired level of animal performance providing animal food supplies containing mineral elements is essential. For this purpose, mineral elements of 8 important rangeland species, including Ferula ovina, Prangus uloptera, Medicago sativa, Lotus goeblia, Trifolium montanum, Melilotus officinalis, Sanguisorba minor and Stachys inflate, were measured at different growth stages in the summer pastures of Taleghan. Therefore, at each growth stage 3 samples were taken and for each sample at least five vegetable bases were removed from different vegetation types. Data were analyzed using one-way ANOVA and to see the sources of variation within groups the Duncan test was utilized. Moreover, T-test was used to compare the values of mentioned elements with the critical level to provide the daily requirements of an animal unit in the maintenance mode. The results show that the values of minerals at the early stages of growth are more than those at the final stages of development (seeding stage). Moreover, the mentioned values in each stage of the growth are not uniform among the studied species. In general, the studied species are in good condition in terms of the calcium, iron, copper, cobalt and manganese values for meeting the daily needs of animals. However, they are not in optimal condition in terms of the highly consumed elements such as sodium and magnesium values at different growth stages, especially at later stages of growth, for meeting the daily needs of animals. This indicates that the desirability of grassland forage at different times of grazing is not identical regarding the mineral elements. It is normal that depending on the year’s conditions the values of plant mineral elements may change slightly; however, due to the cost of determining mineral elements, the results can be used to estimate the daily animal needs in different years.
Seyed Hamzeh Hosseini Kahnuj; Reza Erfanzadeh; Hossein Azarnivand
Abstract
This study aimed to investigate the effect of habitat kind on soil seed bank characteristics viz. density diversity, richness and similarity between seed bank and above ground vegetation. Two different habitats (grassland and forest) were selected in Vaz, Mazandaran province. The grassland habitat located ...
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This study aimed to investigate the effect of habitat kind on soil seed bank characteristics viz. density diversity, richness and similarity between seed bank and above ground vegetation. Two different habitats (grassland and forest) were selected in Vaz, Mazandaran province. The grassland habitat located in the upper end of the forest habitat, adjacent to each other. Then in each habitat, 7 transect perpendicular to slope gradient with 25 meter distance between transect were established; 10 1*1 m plots were selected along each transect. In each plot, 10 soil subsamples were collected and divided into two depths: 0-5 and 5-10 cm. soil sampling was done in winter, 2010. Soil samples were then transferred to and spread in the greenhouse. Germinated plant species were identified, counted and then removed. On the other hand, the above-ground cover of plant species in each plot was recorded in the next growing season. Finally, the number of seeds germinated in the greenhouse was recalculated per meter square and then the similarity between seed bank and aboveground vegetation was calculated in each plot using Sorenson similarity index. Non-paired and paired t-test was applied to compare soil seed bank characteristics between the two habitats and between the two depths, respectively. The results showed that all seed characteristics (with the exception of similarity between aboveground vegetation and soil seed bank in depth 5-10 cm) were significantly higher in grassland than forest. The lower seed characteristics in forest habitat could be related to lower seed input to soil, higher litter percentage and moisture in the above ground of forest habitat. These factors particularly soil moisture and litter could encourage the decomposition of seeds before penetrating soil. In total, the seed of only two shrublands species were germinated in the greenhouse.
M. Padyab; S. Feiznia
Abstract
Importance of sediment storage has been expressed as being higher than that of water in floodwater spreading networks. To determine the contribution of each geological formation in sediment input of Gachsaran Floodwater Spreading Station after 12 years of flood spreading, sediment sampling was conducted ...
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Importance of sediment storage has been expressed as being higher than that of water in floodwater spreading networks. To determine the contribution of each geological formation in sediment input of Gachsaran Floodwater Spreading Station after 12 years of flood spreading, sediment sampling was conducted in 16 points and 0-15 cm depth of the field. Using dry sieve analysis, all samples were analyzed for granolumetry. To determine mineralogical composition of sediments, particles on 150 and lower than 62 micron sieves were used. The lithology of formations was identified using geologic maps. The mineralogical composition of samples was also compared with lithological units of upstream watershed. Then percentages of share of each lithological unit in sediment production were determined. By considering the area of each lithological unit, weighted percentage of share of each unit was calculated. The results showed that Pabdeh-Gurpi formations with 55.3 % of the sediment input, has had the most contribution in the production of the largest particle size of 150-300 micrometers, followed by Kazhdomi formation with 14.1% share, Ilam-Sarvak formations with 13.1 % share, Khami formation with 10.8 % and Asmari formation with 6.5% share in the sediment production, respectively. With regard to the particles size less than 62 micrometers, Pabdeh-Gurpi formations with 80% of input sediment, had the largest contribution in the production of these particles. By using erosion control measures and storing sediments of streams on Pabdeh-Gurpi formations, 80% of very fine sediments (less than 62 microns) and 50% of fine sediments (150-300 micrometers) will be decreased.
Hamed Rouhani; Mohsen Farahi Moghadam
Abstract
In the past decades, much effort has been devoted to simulation of the rainfall-runoff process. Hydrological models are simplified representations of the natural hydrologic system. In each case, the choice of the model to be applied depends mainly on the objective of the modeling but also on the available ...
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In the past decades, much effort has been devoted to simulation of the rainfall-runoff process. Hydrological models are simplified representations of the natural hydrologic system. In each case, the choice of the model to be applied depends mainly on the objective of the modeling but also on the available information. The relative performances of two lumped conceptual-based hydrology models (Tank and SYMHYD) were compared based on daily data of Chehel_Chay catchment in the northeast region of Golestan province. As in Tank and SIMHYD models, parameter spaces are high dimensional, it is difficult to obtain optimal parameters using manual trial and error procedure. These parameters need to be estimated through an inverse method by calibration. Therefore, an automatic optimization procedure based on the Genetic Algorithm (GA) was tested for parameter calibration of two models. For testing the applicability of the model in gauged basin, the model was calibrated for a period of 1992–1996 and validated for a period of 2002–2005. The result showed that RMSE of discharge predictions were as low as 0.821 for a Nash-Sutcliffe coefficient of 0.599 for the Tank model, against 0.819 for a Nash-Sutcliffe coefficient of 0.602 for the SYMHYD model in calibration period. When evaluating the model performance in validation period, SYMHYD model is performing most accurately with RMSE=0.490 and E=0617. It was found the RMSE for Tank model is 0.522, which is slightly higher than SIMHYD (RMSE=0.490). SIMHYD is performing most accurately with E equal to 0.602 and 0.607 in calibration and validation periods, respectively.
