نشریه پژوهش های آبخیزداری
پیاپی 113 (زمستان 1395)

One of the most important plans for range improvement is the production of suitable seeds. To achieve this goal and to detect highest germination rate the harvesting time should be regulated, so that the seeds must be both matured and not scattered. In this study the optimal dates of seed harvesting of three range plants including Salsola rigida, Zygophyllum eurypterum and Ferula ovina are investigated. Seed harvesting was done in different stages from physiological maturation time to seed falling. S. rigida seeds were collected on September 22th, 29th and October 6 th, 13th and 27th and November 3th and 10th at 2004, and Z. eurypterum and F. ovina on June 30th and July 7th, 14th and 21th at 2005. From each stage 400 dried seeds in four replications were tested in petridish. Germinated seeds were counted during 21 days.
The results of this experiment showed, there is a significant difference between various seed harvesting times of S. rigida. The highest germination rate of this plant is on Nov. 10th (75%), and the lowest rate is on Sep. 22th (7.3%). No significant difference was detected for Z. eurypterum. The highest rate of germination of Z. eurypterum was on June 30th (61%) and the lowest one was on July 21th (46%). F. ovina seeds had the highest rate of germination (54%) on July 21th and the least rate of germination on June 30th and July 14th (37%). There is also a significant difference in harvesting rate of this plant referring to different times. According to the achieved results of this study, harvesting delay increases germination rates of S. rigida and F. ovina, while this parameter has no effect on Z. eurypterum. This variable is considered as a clue in selecting optimal time of seed harvesting.

A large part of Iran's formed mountainous areas, so each year, landslides cause damage to structures, residential areas and forests, creating sedimentation, mud floods and finally cause filling reservoirs. Since forecasting of the landslide occurrence is out of human knowledge in both temporally and spatially, so the landslide zoning is considered in order to be shown how much a mountain slope is susceptible to a mass movement. In this study, nine factors including slope percent and aspect, geology, precipitation, distance from the road and the river and faults, land use and elevation were used. The purpose of this study is to determine the most effective factor on landslide occurrence and preparation of landslide susceptibility map in a Part of Haraz Watershed. In this study for determining the most effective factor influencing on landslide occurrence and finally preparing of the landslide susceptibility map Analytic Hierarchy Process (AHP) and Artificial Neural Network (ANN) were used. From seventy eight points of slide and seventy eight points of un-slide determined in this area, seventy percent used for modeling and thirty percent for testing. Firstly, for providing aforementioned layers, Geographic Information System (GIS) was applied and then each of classes specified in every layer was valued using frequency ratio. In this study, for network training used Back-Propagation (BP) algorithm and sigmoid function. The results of the Analytic Hierarchy Process showed that slope is the most importance factor among studied factors. The results of the Artificial Neural network showed that structure 9-14-1 whit learning rate 0.2 is optimal structure and Root Mean Square Error is 0.051. Accuracy of network in training and testing phase was equal 92.307 and Coefficient of Determination was equal 0.962.

Improper and inadequate usage of not-renewable resources and drought has prepared condition for degrading of vegetation cover and desertification. Herein control and flood spreading project that could be applied in more deserts is an appropriate solution to this problem. On the other hand, different parameters including slope gradient, soil texture, vegetation cover and flow resistance affect on flow hydraulic characteristics. In this study, seasonal floods are spreading with spreading channels which is constructed on contour lines. This study carried out in the Gareh Baygan plan, in the south east of Fars province to investigate the effect of slope steepness on critical distance for scouring. An open hydraulic flume with 100 meter length, 40 centimeter width and 25 centimeter depth was used to simulate overland flow with 10 centimeter depth. Five treatments including 0.002, 0.004, 0,006, 0.008 and 0.010 for slope were examined, and for each treatment, three to four experiments were used and some hydraulic parameter including discharge and flow depth were measured directly, and others such as flow area and flow velocity were calculated. After each experiment erosion and sedimentation depth were measured individually. Results of this study show that threshold value will be increasing with increase slope gradient. Average distance of erosion threshold obtained for different treatments 66.5, 56, 45, 36 and 28, respectively. Likewise, flow velocity was increased with flow length. Also, this increasing trend was linear and uniform and changed according to bed slope and roughness and reached the maximum value in each experiment.

In order to study the effect of rangeland improvement operations on vegetation properties, a study was conducted at Imam Kandi rangelands. In the present study, improvement operations including pit seeding, exclusion and counter trenches were selected at region and control region was considered for each region. the systematic-randomly method was used, six 100 m transect was established on each sites and along each them ten 10*10 plot for sampling was selected. Within each plot, existing species table, crown cover percent, palatability classes, production, density and vegetation growth forms was recorded. In order to comparison of vegetation properties at sites with improvement operation within control site independent t-test was used. Results showed that plants in classes I and II at improved regions increased and plants III decreased compared to control and had significant difference. In terms of growth forms, mean properties of permanent graminea and permanent forbs at improved region increased and had a significant difference with control site. Overall, results show that improvement operation at Imam Kandi rangelands was successful and caused improvement of vegetation cover properties in these rangeland area.

Soil hydraulic properties have key role in sugar cane cultivation management. The purpose of this study is to estimate soil moisture characteristic curve using an artificial neural network and its optimization with genetic algorithm. Therefore, based on the cultivation operations management and soil properties included: organic matter content, soil texture, electrical conductivity, sodium adsorption ratio, 4 land unit tracts in Debel-Khozaii, Amir-Kabir, Karoon and Haft-Tapeh agro-industries were selected. A total of 310 soil samples from both 0-40 and 40-80 cm of soil profiles were collected. In this study, five models were arranged in hierarchy to estimate soil hydraulic properties with ANNs. The performances of the models were evaluated using Spearman's correlation coefficient (r) between the observed and the estimated values, normalized mean square error (NMSE), and mean absolute error (MAE). Owing to the fact that the selection of each of the variable parameters of neural network necessitated recurring trails and errors, and consequently teaching a large number of networks with various topologies, genetic algorithm method was utilized for finding the optimization of these parameters and the efficiency of this method was examined in terms of the optimization of neural network. Results showed that the neural network has a high degree of accuracy in modeling and estimating soil moisture characteristic curve (R =0.943, MAE=0.019, NMSE=0.054). Also, combining artificial neural networks with genetic algorithm for optimizing the conditions of the artificial neural networks implementation was positive and combining approach indicated its superiority over non-optimized implementation of artificial neural networks in all cases (R=0.985, MAE=0.01, NMSE =0.0151).

Nowadays, evaluation of soil and water conservation projects are the most fundamental issues in order to increase the efficiency of natural resources planning and management. . Due to lack of necessary equipment and tools to measure and record changes induced by critical phenomena such as flooding and degradation, application of models to evaluate different management scenarios aiming to attain the goals is inevitable. Purpose of this study is assessment of the impacts of vegetation-based management scenarios on hydrologic responses of the Ghazaghli watershed using the SWAT model. To this end, four management actions including terracing, afforestation, orchard plantation and agroforestry were chosen. Different combination of these four actions leads to 16 (2n) different management scenarios. Rationale method was used to estimate runoff depth and SCS method was used to estimate volume of runoff. Furthermore, the Muskingum and FAO Penman-Monteith methods were used for flood routing and estimation of ETo, respectively. The simulation of all possible scenarios indicated that a scenario combining all management actions (scenario 16) is the most effective scenario in reducing runoff. Whereas this scenario leads to 13/15 percent reduction in the annual runoff volume.. Among the individual scenarios, the scenario 5 with Agroforestry action resulted in the largest decrease in the annual runoff which was 11.6 percent. The largest reduction in monthly runoff has occurred during June and July. This period of year coincide with the maximum growth of vegetation cover which induce the increase of evapotranspiration and consequently decrease runoff volume.

Medicinal plant of Aloe vera L. are used in food, healthy, cosmetic and medical industry. Pot sowing is one of the production methods of this plant. In this conditions evaluation of different urea level on yield and yield component in pot sowing essential. For this purpose, an experiment was conducted as a completely randomized design in five levels of nitrogen fertilizer as urea (0, 50, 100, 150 and 200 kg.ha-1) with three replications (10 pots for each replication) in the greenhouse in 2010. In this experiment, traits such as leaf length, of width, thickness, number and shoot number, total biomass, weight and percentage gels were studied. Analysis of variance based on the effect of nitrogen on total biomass, weight of gel, leaf width and number was significant at the one percent level and characteristics of the gel percentage and leaf length at the level of five percent was significant. But effect of nitrogen on leaf thickness and number of shoot traits, was not significant. The highest biomass production was obtained at 50 kg.ha-1 N with 1039 g per pot. The highest gel weight (839 g) was obtained at 50 kg N. Gel percentage production was 72.7% at this level of nitrogen application and did not have significant difference with 100 kg N treatment.

Watershed management practices (WMPs) include methods to create, enhance, and maintain vegetation to reduce surface runoff in the watershed. The implementation of WMPs at the watershed scale is an ongoing challenge that needs to take into account trade-offs between hydrological and economic objectives using optimization algorithm. This research demonstrate a methodology and decision support tool that suggests the optimal location of biological watershed management practices (including improvement rangeland cover) which minimize the cost and simultaneously reduce surface runoff to target levels cases (i.e. 10%, 15%, 20% and, 25%) at watershed scale. The decision support tool (SWAT-GA) consists of a semi-distributed hydrologic model, Soil and Water Assessment Tool (SWAT) which simulation of runoff in watershed, a genetic algorithm (GA), which serves as the optimization engine for the location of biological watershed management practices across the rangeland of the watershed. The proposed method was then applied to Taleghan watershed with an approximate area of 900 km2 that located in Alborz Mountain, Iran. Results indicate watershed management practices should use in 22%, 35%, 48% and 62% of total area of watershed to reduction 10%, 15%, 20% and 25%, respectively. The maximum decrease and increase runoff after the implementation of WMPs have been occurring in the spring and summer, respectively. Using this decision support tool, for each level of target goals, decision makers can select the optimal combination of watershed management practices.