Watershed Management Research
Year:2012 | Volume:24 | Issue:4 (93)|Papers Count:10

Recognizing the susceptible areas for natural hazards is one of the primary steps in natural resources management and Development program schematizations. Assessing existing and future of disaster states can facilitate the design of disaster management organizations. Liquefaction is an important geotechnical phenomenon that usually takes place in saturated loose sandy soils due to increasing pore water pressure and decline soil resistivity. In this research liquefaction hazard potential in west of the Golestan province was evaluated. After processing data and base maps in GIS environment, SWM model was used for producing hazard maps with (20×20m) pixel size, for existing condition.Considering alterations in future water level and seismic acceleration, 7 different scenarios were developed, and hazard maps for these scenarios were obtained. Then area percent around five towns in hazard classes was calculated. The results of statistical comparison show that significance different exist between the hazard classes in different scenarios.The results indicates that the minimum and maximum Liquefaction hazards after earthquake event respectively occurs in 1 and 8 scenarios in Bandar-Torkaman and Bandar-Gaz areas that are in proximity of surface earthquake center and Caspian Sea coasts.

Determination of forage quality of available species is one of the fundamental factors for the management of rangelands.The forage quality of rangeland species in variant site and time was different. Because various factors affect in quality and nutritive value. From this factors can be mentioned to various stages the phonological in vegetation growth. The present search was conducted to evaluate the forage quality of Frankenia hirsuta at saline and alkaline habitats of inched-borun area in Golestan province. The study area has -4 m elevation and 304 mm annual rainfall. During the study samples were collected for Frankenia hirsuta in three phonological stages of vegetation growth, flowering and seed ripening stages in three replications, the quality indices of dry matter digestibility (DMD), crude protein (CP), crude fiber (CF), metabolic energy (ME) and slage were measured. Then these quality indices in three phonological stages compared with ANOVA and Duncan analysis. The results showed that in these species, forage quality in stage of vegetation growth was higher than flowering and seed ripening. The rate of crude protein (CP) and metabolic energy (ME) at vegetation growth stage higher than two stages. With regard to nutritive value and palatability this species, can be used of this plant at forage production programs.

The allelopathic influence of aqueous extracts of Thymus kotschyanus on Bromus inermis and Agropyron elongatum germination (%), germination speed and seedling growth was examined. In other to this, at first extract from shoot and roots of Thymus kotschyanus was prepared. The extract was diluted by adding distilled water to 5, 25, 50 and 75 percent. The effect of the above concentrations, as well as distilled water as control were studied on seed germination using a completely randomized design. Results indicate that there were significant differences among the treatment for germination percentage and speed, length of root, length of shoot, length seedling and vigority index (p<1% and p<5%). Comparison of means indicated that the most amounts of germination speed and percentage and other studied indices related to control treatment and the lowest amounts belonged to treatment with 75 concentration percentage of Thymus kotschyanus. The increasing of concentration of the Thymus kotschyanus extract significantly decreased germination and seedling growth in both species and Bromus inermis had more sensibility than Agropyron elongatuminrelated to allelopathic effect of Thymus kotschyanus.

The purpose of current study is to investigate the effects of some of environmental factors on erosion value, to find the most important governing factors and the relation between erosion of working units and environmental factors (soil characteristics, slope, aspect, elevation, lithology, geomorphology faces and vegetation cover percentage).Working units map was prepared using geomorphology method. This map was derived by overlaying slop, aspect, elevation, lithology and geomorphology faces maps. In order to study plant cover random-systematic sampling in each working unit was conducted in 10 plots. Regarding the species type and distribution the area of each plot was determined based on the minimal area method. Canopy cover of species was determined in each plot. Furthermore, 5 profiles were sampled within the working units to study soil characteristics in 0-50 cm depth. Subsequently, the texture, percent of lime, organic matter, gravel, pH and EC were measured. Erosion value was determined in each working unit using E.P.M. method. Statistical analysis was done using the Principal Components Analysis (PCA) through PC-ORD4 software program. The results showed that among environmental factors, vegetation cover, slope, stone resistance, organic matter and aspect as the first set of factors determine the change in erosion value by 54.35% while the second set of factors, including loam and clay percentage play contributes to the change by 26.96%. These two sets of factors altogether explain 81.31% of erosion value variation in Ghara aghaj basin.

Ground cover and plant density data are required for many management plans in rangeland utilization. Introducing a proper method with low field work and costs and expert biases in addition an adequate accuracy, is important. In this study according to development of usage of new softwares for digital image analysis, possible use of photographic method for measurement of ground cover and plant density was investigated. To conduct this study four vegetation types (two grasslands and two grass- shrub lands) in Taleghan region were selected. In other to measure ground cover, ocular and photographic methods and for plant density measurement direct (counting) and photographic methods were used. Data were collected within 60 plots of 1 m2 along 6 transects 200 m in each sites. Interpretation of pictures of plots was done using Arc View software. Data analysis was done by SPSS software using paired t test. Generally, the results of this study showed that photographic method for measurement of ground cover in grass-shrub communities is applicable. But in grassland communities for measurement of canopy cover, based on variance between two methods and precision and aim of research, application of photographic method should be with care. In addition the results showed that, there were not significant different between density estimated by two methods (P<0.05). Then photographic method could be used for density measurements in similar vegetation communities.

Watershed management structures are expensive projects that are built with purposes of erosion and sediment reduction and flood control in watersheds. Quantitative assessment of watershed management activities in order to analyze their impacts and making basic decision for implementation of these activities are necessary. As building any structure on bed of dry rivers can effect on river behavior, then, this research was done with aim of investigating the effect of check dams on flooding in Manshad watershed. Therefore, the HEC-HMS model was used for comparison of discharge variations with/without checkdams construction. To determine the effects of check dams, the concentration time (after building the structures) was computed and by changing the input parameters, the flood behavior was simulated. Moreover, model was validated and calibrated by six observed event and flood hydrograph was simulated for return periods of 2 to 100 years before and after the structures operation. To evaluate the effect of checkdams on flooding, the peak discharge and flood volume indices were determined for two conditions (before and after the structures operation).Based on the simulation results, the effect of structures on reduction of peak discharge and flood volume were 9.82 and 7.75%, respectively. On the other hand, by increasing the return period of flood, the structures effects on the reduction of peak discharge and flood volume have been decreased as the rate of variations in return periods of 2 to 100 years have been 14.14 till 6.95.

The purpose of this study was to investigate the effects of different treatments on seed germination in; Atriplex canescensand Atriplex lentiformis. An experiment was performed using 12 treatments and 4 replications in a completely randomized design. Treatments included KNO3 with concentrations of 0.1 and 0.2 percent for 72 hours, sulfuric acid (60%) for 5 and 10 minutes, immersion in hot water for five minutes, acetylsalicylic acid 100, 200 and 300 mg L-1, pretreatment with thiourea (SC (NH2) 2) 0.1 and 0.3 percent for 72 hours and prechilling for 20 days. distilled water was used as the control. Germination properties included germination percentage, germination rate and mean germination time. Our findings indicate that 0.1 KNO3 and 100 mg L-1 acetylsalicylic acid were the most effective treatments for improvement of seed germination percentage inA. lentiformis and A. canescens, respectively.

In order to determination of a rangeland ecosystem function and potential, studying the effect of relation between plant and soil is essential. Soil features directly effect on vegetation. The other hand factors such as plant species, growth form and vegetation density effect on soil features. So, the aim of this research is studying the effect of plant with different growth forms on soil surface features in semi-steppe rangeland in Golestan National Park. Using Landscape Function Analysis (LF (, 11 soil surface features in three growth forms including shrub, wheat grass, forbs and mixture of shrub and wheat grass in five replications were measured. Then according the three indices of stability, permeability and nutrient cycle, for each growth form they were classified. The results showed that shrub form more increase soil surface stability to others forms.Permeability showed no significant differences among the three growth forms. The soil surface of wheat grasses had the higher percentage of nutrient cycle, but the difference with others was not significant. Due to high stability of soil in shrubs and mixture of shrub-wheat grass, these species can be used for breeding operation in semi steppe rangelands.

Particle size distribution (PSD) and aggregate stability are dynamic soil properties, which changes with time. This study investigates the effect of different organic matters on PSD variability. The experiment was carried out using factorial method in a randomized complete design with two treatments of organic matter (straw stubble and pistachio residue), three levels of 0, 1 and 5 %w, three time steps (40, 80 and 120 days) and three replicates. In addition, soil PSD was measured in two manners of dry (DPSD) and wet (WPSD). The results indicated that studied treatments had different influence on the PSD, which depends on type and amounts of added plant residue macro aggregates frequency increased. Also, the control and straw stubble (5%) treatments with median sizes of 0.228 and 0.394 mm, resulted in the least and highest effect on DPSD, respectively. The results of DPSD variability showed that for all of the treatments, the frequency of smallest particles (<0.125 mm) decreased significantly, while the WPSD had no changes with time. In comparison with the DPSD which 0.125-0.25 mm particles were the most frequent, for the WPSD this range shifts to the fraction of <0.125 mm. This finding indicated that the DPSD and WPSD have not the same trend. In addition, Nitrogen utilization led to some changes in DPSD, whilst this effect was insignificant for the WPSD. The findings of this study reveal that following application of any type of organic matter, a range of particles size is most influenced. Taking into account the influence of time in aggregate studies is suggested.

Rain-gauge networks are often installed to provide measurements that characterize the temporal and spatial variations of rainfall, thus accurate and efficient design of them are necessary. The main objective of this research is to evaluate the rain gauge network installed and administered by the Ministry of Energy in the Golestan province (39 rain gauge stations during 12 years), using spatial correlation technique. Considering the effects of topography on precipitation pattern, the Golestan province has been divided into two homogeneous areas. In each area the correlation functions based on correlation between monthly rainfall data and distances of stations have been determined and the accuracy of spatial rainfall estimation with the running rain gauges have been evaluated using two accuracy criteria (Ac1 and Ac2). Then, depending on the desired level of accuracy, the required number of rain gauges and their distances and spatial pattern were estimated in both homogeneous areas. Results showed that the present network of rain gauges in the mountainous area has more suitable spatial pattern than the flat area. Also it has been concluded that the existing network of rain gauges would suffice the objectives of management and research studies that require data with 10 to 15% accuracy level. However, in case of need for more accurate estimation of spatio-temporal variations of rainfall, the number of rain gauges in the mountainous area should be increased. While, in the flat area relocation of existing rain gauges is necessary.