Morteza Shahnori; Maryam Azarakhshi; Mehdi Bashiri; Hasan Rezaee Moghadam
Abstract
Evapotranspiration as an important component of the hydrological cycle plays a major role in the study of water balance in watersheds. The purpose of present research was to investigate the response of Atriplex canescens to different levels of water salinity and the effect of irrigation water salinity ...
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Evapotranspiration as an important component of the hydrological cycle plays a major role in the study of water balance in watersheds. The purpose of present research was to investigate the response of Atriplex canescens to different levels of water salinity and the effect of irrigation water salinity levels on actual evapotranspiration under lysimetric conditions. For this purpose, four treatments inclusive 0, 25%, 50%, and 75% of maximum salinity tolerance of Atriplex canescens with 3 replications were considered which equal as zero, 19.6, 39.2, and 58.8 ds/m of Sodium Chloride. The lysimeters were placed in greenhouse and two Atriplex canescen shrubs were cultivated in per lysimeter. 5 liters of water with mentioned salinities were added to each lysimeter every two weeks. During the vegetative period of the plant, from 6th March to 15th of August of 2019, the measurement of evapotranspiration was done by weighing the lysimeters at intervals of one week. After the end of the experiments, the weights of shoots and roots of each treatment were measured in wet and dry situation. The results showed that evapotranspiration decreased from 3.94 to 2.84 liters with increasing salinity of irrigation water from zero to 58.8 ds/m, and there was a significant difference between control and 58.8 ds/m salinity treatments at 5% level. By increasing salinity from 0 to 19.6, 39.2 and 58.8 ds/m, the dry weight of shoots increased compared to control treatment 20.13%, 41.87% and 11.55% respectively. Therefore, with the conditions of the present researchو Atriplex Canescens was produced the highest amount of dry shoot in 39.2 ds/m salinity.
parisa farzi; maryam azarakhshi; ali rasoulzadeh; mehdi bashiri
Abstract
Characteristics of stones forming the earth's surface contribute significantly to environmental changes such as soil erosion and movements of soil particles. This study seeks to investigate the main and reciprocal effects of geological units and slope gradient on runoff and sediment production in Senobar ...
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Characteristics of stones forming the earth's surface contribute significantly to environmental changes such as soil erosion and movements of soil particles. This study seeks to investigate the main and reciprocal effects of geological units and slope gradient on runoff and sediment production in Senobar watershed using rainfall simulator. To this aim, the geological map was created in Arc GIS 10 software and three dominant units i.e. green tuff, sandstone, marl (Et), Orbitolina Limestone (Kl) and Conglomerate, Sand stone (Ngcs) were identified. Besides, to study the effect of slope gradient, the slope map was provided in three classes: 0-10, 10-30 and more than 30%. Then, the rainfall intensity equal to 0.9 mm min-1 (10- years return period) was created by rainfall simulator. Analysis of variance showed significant differences between geological units for runoff, sediment yield and sediment concentration at 5% significant level. It was found out that there is significant difference between different slope gradients in runoff and sediment production; however, there was no significant difference regarding sediment concentration. The results of interaction between geological units and slope gradient for runoff volume was significant at the 95% level of confidence but regarding sediment yield and sediment concentration interaction effects were not significant. Generally, it was found that the type of geological units and slope of the study area impacted on soil erosion process. Also, the impressibility of runoff variable was more than that of the sediment.
Maryam Azarakhshi; Mohammad Mahdavi; Hasan Ahmadi; Hosein Arzani; Jalil Farzadmehr
Abstract
Plants cover composition, condition, trend, production, and grazing capacity of the rangeland change annually. In this research, the role of temporal rainfall distribution on rangeland production was assessed. This research had down in the rangelands of Ilam (with semiarid to semi humid climate) and ...
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Plants cover composition, condition, trend, production, and grazing capacity of the rangeland change annually. In this research, the role of temporal rainfall distribution on rangeland production was assessed. This research had down in the rangelands of Ilam (with semiarid to semi humid climate) and Qom and Markazi (with arid to semiarid climate) provinces. By attention on plant cover maps in each province 10 main types of plant cover in Ilam, 8 types in Qom and 10 types in Markazi were selected. In these sites, relative factor to plant cover and soil contains: canopy cover, density, production, germination and, soil cover were measured along four 400m transects into 60 plots .the production of the graze able species was measured by clipping and weighting method. The regression techniques and correlation coefficient were used to the relation between production and precipitation. to determination the role of the temporal distribution of rainfall of the rangeland production, the relationship between rainfall and production was calculated in seven time steps contains. The results show that only 4% of the total forage production is explained by annual precipitation but in 96% cases there were related with start of growth season (March) and growth season(early March to late July).this result shows the importance of growth season precipitation on the forage yield in rangelands.
Maryam Azarakhshi; Jalil Farzadmehr; Mahdi Eslah; Hossein Sahabi
Abstract
Climate change is defined as long term and irreversible changes in the climatic behaviorof a region. Many studies have been conducted in different regions of the world on climatechange. The results of these studies show considerable changes in climatic factors especiallyin precipitation and temperature. ...
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Climate change is defined as long term and irreversible changes in the climatic behaviorof a region. Many studies have been conducted in different regions of the world on climatechange. The results of these studies show considerable changes in climatic factors especiallyin precipitation and temperature. In this research, the trend of changes in annual and seasonalrainfall and temperature in 24 synoptic stations over a 50-year data period (1956-2005) wasinvestigated in Iran. The Mann- Kendall test and linear regression technique were used to analyzethe trend of changes in climatic factors. The results showed both increasing and decreasingtrends in annual rainfall at various regions of Iran. Annual rainfall in northern slopes of Alborzand western slopes of the Zagros Mountain as well as in eastern and southeast parts of Iran hada decreasing trend while in the central of Iran the trend of changes was increasing. In southernregion of Iran the rainfall had an increasing trend. The results also showed that temperature inmost of the studied stations over the considered period was increasing. The highest and lowestchanges in temperature were seen in the mean temperature of summer and winter, respectively.Ahwaz and Khorramabad stations had a decreasing trend and over all seasons would go towardmore cooling. The temperature trend in Oromiye was decreasing in autumn and summer whileShahrekord and Bandar abbas had the same trend in summer and winter.
Maryam Azarakhshi; Behnoush Farokhzadeh; Mohammad Mahdavi; Hossein Arzani; Hassan Ahmadi
Abstract
Iran is located in dry belt of the earth and always involved with drought in different sections. Drought has already caused many losses to natural plant cover, agriculture and human society. For drought monitoring, we can use some drought indecies. In this research, the Standard Index of Annual Precipitation)SIAP),Sandardized ...
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Iran is located in dry belt of the earth and always involved with drought in different sections. Drought has already caused many losses to natural plant cover, agriculture and human society. For drought monitoring, we can use some drought indecies. In this research, the Standard Index of Annual Precipitation)SIAP),Sandardized Precipitation Index (SPI) and Palmer Drought Severity Index (PDSI) were used for assessment of drought effects on rangeland plant production. The research area is located in Qom province that contains eight rangeland sites. Plant production and soil factors were measured in rangeland readiness period from 1997-1998 to 2005-2006 annualy. Regression techniques were used between drought indices and total production and also production of different vegetation forms in seven time scales (early March to late July (growth season) and early February to late July (growth season and the previous month), March to June, March to May, March to April and March (start of growth season). The best drought index was then selected based on the highest correlation coefficient and lowest standard error. The result showed that the best drought indices in Qom rangelands are SPI-3, PDSI, SPI-24 and SPI-6, respectively. Also the most significant time step was resulted growth season and specially early stage of growth season.
