نشریه پژوهش های آبخیزداری
پیاپی 111 (تابستان 1395)

According to determine the factors influencing carbon storage in different land uses in Shahriar, different treatments of cultivation, age and land use, also grazing intensities were selected. These treatments included 18-year old Atriplex exclosure, mean and high grazing intensities, 8-year old Atriplex mean grazing intensity, 3-year old Atriplex exclosure and mean grazing intensity, 2-year old Atriplex exclosure, 8-year old Haloxylon exclosure, rain fed wheat, irrigated barley and control treatment (natural rangeland). after specifying the amount of carbon stored in ecosystem, also some soil and plant properties of study area, the most important factors associated with carbon storage, were tested using PCA test and PC ORD software. Results showed that the most important factors influencing carbon storage are clay of the 2nd and 3rd depth and HCO3 of 2nd depth, also N of 2nd depth, EC of 3rd depth, above ground biomass weight and root carbon. Irrigated barely and exclosure of 18 year old Atriplex fields have the most carbon content, which depends on clay and HCO3, on the other hand, Carbon is related to EC and root carbon in exclosure of 8 year old Atriplex fields.

In semi-arid regions water resources systems are more vulnerable due to climate change and human activities, and based on this, knowing the basics of interaction between groundwater and surface water is essential for effective management of water resources in these regions. There are several models to simulate this phenomenon, each of which has its own problems and shortcomings. This study aims to simulate groundwater flow in Gotvand - Aghili plain using the River Package of MODFLOW model. First, aquifer was simulated in steady state. Then, using the data of water table from October 2007 to September 2008 the aquifer was calibrated in the unsteady-state. Next, by using the calibrated model in unsteady-state and data of water table from October 2008 to September 2009, the model was verified. After that, the interactions between aquifer and Karun River in different scenarios including the impacted of two dams Gotvand and predicting the interaction of aquifer and the river during the dry and wet periods was investigated by zone budget method in modflow. Afterward, the Karun river reach in the study area was divided into seven zones and water balance was assessed in each of them. Results indicate that the river is draining the aquifer in the northern and especially central parts of the plain and recharging it in the southern zones. Aquifer – river exchanges are mostly affected by the river water level fluctuations.

Aeolian sediments are in 6 percent of land and 97 percent of them are in arid land. On average, about 20 percent of the arid regions of the world are covered by these. Prevailing winds can shift sand dunes and affect their accumulation. According to sediments have damage and harmful effects on the living then study of this subject is significant importance. In this research with Fryberger method and used of WR PLOT 7.0 and MATLAB 2013 software in order to assessment of wind regime as well as used from anemometer data of five station near Kashan ERG. Results indicate that east-west winds are dominant and each station shows a kind of wind regime. The frequency of calm winds increases respectively in station of Jngalbani (32.77), Qom (40.05), Garmsar (44.83), Ardestan (50.15) and Kashan (77.04). After calm winds in the area, the most of class is 11-7 Knot, while the most effective class is 17-11 knots (992.6 Erode Index) for wind erosion in the region. Jangalbani station with 441.81 VU and kashan station with 40.02 VU are the highest and lowest quantity of sand drift potential in the region. Comparative studies on various stations in the world according to sand drift potential in the area indicated that kashan ERG is not hazardous then in general, could say that it located in the low-middle class. And the formed of linear and transverse dunes near Kashan and Jangalbani station following a global trend. Result show taht there is note full compliance beatwen Fryberger method and Sand Rosr Graph 3.0 software.

In the management water resources science, optimal Operation of existing water systems, such as dams, every day is more important. Due to budget and operational water resources limitations and environmental problems, optimize operation of these systems are gradually replaced by new systems are constructed. Optimal Operation of water resources is a Complex, nonlinear, multi-constraint and multidimensional optimization Problem, so to solve them robust optimization techniques needs are needed. In this study Genetic Algorithm optimization has been used in operation of the Mahabad reservoir Dam in Northwest of Iran. The objective function is minimization of difference between downstream monthly demand and release. Early; Sensitivity analysis of GA model performed by considering of various parameters. Then the method was applied considering the reduce probability of inflow to dam for period 24months in the different scenarios. The results show that, the critical condition of drought could managed by the GA model, the optimized model could satisfy downstream watery demand.

Maximum allowable operating range of plants in different climatic conditions, fertile soils with different months in different seasons and in different degrees, because the pasture health is very variable. The purpose of this study was to determine the extent of utilization of Kordan key and the pastures are important. In this first region and a key area of ​​one hectare in area Kordan and In the first year and was grazed, and fencing. Selected and removed from any of 0, 25, 50, 75% and control is exercised (a basic 10 treatments). Monthly by the clipper and the area is grazing season. Effective utilization of changes in the phenological characteristics, forage and seed production, vitality, mortality and other characteristics of selected plant species is. Finally, the combined analysis of data with a split plot design in SAS software was analysed. Results of studies of the effects on forage production and harvest of Bromus tomentellus species studied showed The effect of different levels, different years, and their interactions on the production level is a significant percentage. This shows that in different years with different weather conditions of production are different. According to the research findings, permissible utilization limit of 50 percent in the aspect of plant health was found suitable in the Kordan region.

Plant cover may be the most important factor in conserving the soil from water and wind erosion. Wise management of plant cover needs accurate and sufficient information from vegetation and soil seed bank capacity. Evaluation of changes in vegetation and soil seed bank after a restoration operation can show the role of land management. The relation between these two, indicates the necessity of study the areas after restoration operation. To determine the species richness and similarity of plants and soil seed bank, sampling was done in ungrazed 18 year old Atriplex cultivated area and natural exclosure non-cultivated area. In the fall of 2010 randomized-systematic sampling of seed bank was conducted along four 200 m transects in each region. Five one-square-meter plots with 50 meter intervals along each transect (total of 20 plots in each region) were deployed. Soil samples from the depth of 0-5 and 5-10 cm were collected using auger and transferred to the greenhouse for planting in the proper beds. Plant cover was also estimated and recorded in the fall and spring of 2011 in each plot. Sorenson’s quantitative index was used to measure the similarity between soil seed bank and vegetation cover in each plot. To compare the characteristics of soil seed bank, containing seed bank similarity to vegetation, seed bank richness, palatability classes and life forms, between two regions, unpaired t-test, and between two depths of each region paired t-test were applied. One-way ANOVA and Duncan’s test were used separately to compare the palatability classes and life forms in each region. The results showed that, similarity of plant cover and soil seed bank, also soil seed bank richness in the depths of 0-5 and 5-10 cm had significant difference between planted and non-planted areas. The results also showed that similarity of soil seed bank and plant cover in the planted area is 60% for the first depth and 24% for the second depth. It’s 84% in the first and 40% in the second depth of non-planted area. All palatability classes showed significant difference between two regions. All kinds of life forms except Hemicryptophytes had significant difference between two areas.

Application of lateral intakes has been always considered by human for water supply. The lateral intake is a structure constructed to divert the water from Meandering Rivers for irrigation, storage and industrial purposes, etc. Given that rivers have curvatures in most of their path and also due to secondary flows, external shore of river bend is a good place for intake. An influent weir is constructed at the beginning of intake channel to control the inflow to lateral intake. In this study, to examine the influent weir discharge coefficient to the lateral intake at the river bend, some experiments were conducted in a laboratory rectangular channel with a 180-degree arc made of Plax glass in clear water conditions and without sediments. In these experiments, the effect of variables to the height of the weir at the upstream depth, catchment area at the bend and the Froude number on discharge coefficient of the flow at the inlet span of the intake was studied. The results show that if the bottom sediments inlet to the intake was not proposed, by increasing the Froude number and weir height ratio to the upstream depth, the intake discharge coefficient decreases. The maximum intake discharge coefficient was also observed at 70 and 100 degrees, and at least in 30 and 120 degrees.

Animals feed on natural pastures has always been faced with shortages of forage quality and quantity. For making progress in rangeland management, a better understanding of factors affecting the choice of preferred forage by livestock is essential. Proper planning requires that the range management in addition to changes in forage quality and quantity in different times and places, the preference value and its changes during the season because they are well aware. In order to check the value of semi-steppe vegetation species preferred by Fashandy sheep timing method was used. The manner in which any one day between one and two hours after the arrival of the cattle to pasture in the equilibrium relative because it is preferably 30 minutes of grazing on species film preparation and transmission of computer time grazing any set. Then the data obtained each year using SAS software in a randomized complete block design experiment consisting in the analysis were analyzed using Duncan's multiple domain averages were compared. It can be generally stated that the mean value of the preferred species are significantly different. Based on these results because Bromus tomentellus in Ordibehesh and Khordam months maximum time allotted to that species, Stipa hohenackeriana and Ajuga chamaecistus no significant difference. Species of Amygdalus lacyioides, Asperula glomerata and Achillea millefolium preference value of approximately "are similar in other species were also in the third group.

One of the strategies to combat water resources deficiency and drought crisis, especially in arid and semiarid region is superabsorbents application. This study investigates the influence of some polymers on moisture behavior of two different soils. For this purpose, the experiments were carried out as factorial based on complete randomized design, with three replications. The treatments were included of two types of polymer (Tarawat and Stockosorb), each in five levels (0, 2, 4, 6 and 8 g/kg soil), and two soil textures (loamy sand and sandy loam). After treatment preparation, soil moisture content was measured at 7 suctions of 0, 0.3, 0.5, 1, 5, 10 and 15 bars. The results showed that for all suctions, the type of polymer, level and soil texture had significant influence (P

The amount of forage in the rangelands at different times during the grazing season and in the same year is different. In current conditions, grazing capacity is calculated once for grazing season which may coincides with the maximum production of the range plants. It causes many more livestock entrance during the grazing season in to the rangelands and the result is damaged pastures. The possibility of measuring rangelands production in different months of every year is not possible. Therefore, it is necessary to estimate the amount of forage production during the months of the grazing season, in a few years In order to calculate the long term grazing capacity of rangelands. The aim of this research is determine the seasonal changes in forage production and utilization of range plant Chrysopogon aucheri in during the growing season of the different years. The study area located at 265 meters above sea level far from about 40 kilometers from Bandar Abbas, in the Jevengane Genou. Vegetation type of area is Gymnocarpos decander-Euphorbia larica. For this purpose, inside the enclosure, the forage production of this species was measured every month in growth season. In outside the enclosure the remain forage production is measured and subtracted it from the forage production of inside the enclosure for estimating of consumed forage. The amount of forage production and consumption, after drying in the open air, was weighed and analysed with SAS soft ware.The results showed that, due to the high variability of monthly and annual rainfall, forage production and consumption of this key species in the study area, at the different months and years, have significant difference with each other.