نشریه مرتع و آبخیزداری
سال شصت و پنجم شماره 3 (پاییز 1391)

One of the important factors to make a balance between number of grazing livestock and grazing capacity is whether forage contains sufficient energy and protein during grazing period or not. Therefore in this study, forage quality was evaluated for important species in steppe rangelands of Changuleh located in Ilam province. To do this, samples from four species of Hammada salicornia, Salsola lanchnantha, Convolvulus oxyphyllus and Pteropyrum noeanum, those made considerable components of rangelands vegetation in the region, were collected during three phenological stages (active growth, flowering and maturating) over 2008. Then chemical compositions were determined including crude protein (CP), acid detergent fiber (ADF), dray matter digestibility (DMD) and metabolizable energy (ME). According to the results, maximum CP was obtained from Hammada salicornia in active growth stage. Crude protein component of this species was more than critical level (7%) for sheep in the maintenance condition. Also in this species, ME was in higher critical level (8 Mj/kg) compared with the other species

The effect of exclosure on the changes of vegetation cover of rangelands of Ahmad-Abad region located in Zanjan province has been studied during 2002 to 2006. Three transects comprises of 60 fixed quadrate were establish within exclosure area and outside as well. The changes of vegetation cover were studied to made comparison between the changes of manipulated factors and soil elements using t test. The results showed that total vegetation cover and vegetation cover of shrubs, perennial grasses and forbs of last year had significant difference compared to those of first year within exclosure (p<0.01). But the response of vegetative forms to exclosure, grazing and precipitation were the same. The average density of shrubs within and outside of the exclosure and that of perennial grasses within exclosure of the year 2002 in comparison with those of the year 2002 were significantly different (at a level 0.05 and 0.01, respectively). The comparison of vegetation cover of increaser species such as Crucianella glauca and Artemisia sieberi showed there are significant differences between years 2002 and 2006 within exclosure (significant levels of 0.05 and 0.01, respectively). The decreaser species within the exclosure has been increased compared with outside of the exclosure. Comparison of means of percentage of nitrogen and organic mater at two different depths, inside and outside of the exclosure, showed no significant differences between the start and end years of the study period.

The traditional fuzzy operators, such as t-norms, t-conorms and averaging operators have been used for soil suitability evaluation to aggregate criteria as an overall suitability index. However, such operators do not account for the degree of compensation common to human aggregation criteria, especially in the presence of conflicting criteria. Fuzzy integrals are powerful and flexible aggregation functions that combine the data provided by several information sources based on fuzzy measures. One of the most known fuzzy integrals is the Choquet Integral (CI) that is often used as a nonlinear aggregation tool that takes into account the interactions among the conflicting and interrelated criteria. CI has hardly ever been used in soil suitability evaluation. In this paper, we tested the CI performance as an aggregation operator to evaluate soil suitability for irrigated rice in Lorestan province, western Iran. To conduct standard fuzzy analysis, soil samples were taken from 29 farms under rice cultivation and for the purpose of validation, average dry matters of the three 1×1m quadrates were used to determine the grain yield of rice in each farm. Fuzzy membership values of seven evaluation criteria were combined using CI to obtain a single suitability index in each land unit. In order to validate the results, the soil suitability indices were tested and compared with the results obtained by Lukasiedwicz’s t-norm and t-conorm operator (CLO) by correlation with the measured rice yield. The results show R2 values were fairly high for both aggregated methods, but the soil suitability index obtained by the CI integral has significantly better agreement with rice yield (R2 = 0.83) than those obtained with the CLO (R2 = 0.75). These results call for further investigation of CI as an alternative, and perhaps a better, aggregation operator for soil suitability evaluation.

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

The necessity of using discharge data in hydrological designs and regional programming is an unavoidable matter. Unfortunately, malfunctioning of observation instruments, natural disasters and other problems sometimes result in incomplete or missing data. Having of data related to time series is necessary for every investigation about hydrometeorology. Thus missing data should be estimated in a proper way. There are different methods for generation of missing data which estimates the data with regard to particular parameters. In this study, we have used four methods including linear regression, multiple regression, Longbein method and Thomas-Fiering method for reconstruction of hydrometric data including monthly and annual discharge, sediment and water quality data. Results showed that among various methods, in 192 cases of reconstruction of monthly average discharge of 17 stations, Longbein and multiple regression methods in 33% and 27% of the cases have provided the best results, respectively. Two-variable regression in 8 of 17 stations had the best answer and it is suitable for estimating of annual average discharge. Also results indicated that we cannot use of relation between discharge-water quality and discharge-sediment to reconstruct data using above mentioned methods in the Sefidroud basin.

It is necessary to use empirical models for estimating of instantaneous peak discharge because of deficit of gauging stations in the country. Hence, at present study, two models including Artificial Neural Networks and nonlinear multivariate regression were used to predict peak discharge in Taleghan watershed. Maximum daily mean discharge and corresponding daily rainfall, one day antecedent and five days antecedent rainfall, sum of five days antecedent rainfall and monthly mean temperature were extracted in Gatehdeh, Mehran, Alizan, Joestan and Gelinak hydrological units and entered into neural network model (from upstream to downstream, respectively). The feed forward network was used with one hidden layer and back-propagation algorithm. Then, the models were trained, validated and tested in three stages. The observed and estimated peak discharges of the models were compared based on RMSE and r. The results showed that neural network has better performance than nonlinear multivariate regression.

Remote sensing and aerial photographs are used to produce medium to small scale images. However, for detailed information especially to estimate rangeland vegetation canopy cover there is a need to larger scale images. It is therefore necessary to study the technical applicability of different devices such as short range light airplanes, kites, gliders and balloons. In this research, we focused on suitable flight height for rangeland vegetation canopy cover estimation using large scale balloon images in Incheh Broon area where we conducted field tests in September 2010. The balloons ascended to heights of 5, 10, 25, 50 and 100 m and higher. Using the taken images, vegetation canopy covers were estimated and compared with those obtained from field measurements. Results show that there is no significant difference between field and image estimation of canopy cover for heights lower than 100 m. We therefore suggest using balloon images acquired from up to 100 m height for estimating rangeland vegetation canopy cover.

The current research was carried out to find out the most effective environmental factors in plant species occurrence by classification and ordination methods. For this purpose, the study was conducted in Nir rangelands of Yazd province and topography, climate, soil and grazing intensity data of the region were determined. Sampling method was randomized–systematic and within each sampling unit 3-5 parallel transects with 300-500 m length, each containing 30-50 quadrates (according to vegetation variations) were established. Quadrate size was determined for each vegetation type using the minimal area; hence suitable quadrate size for different species was determined 1*2m–10*10m (2-100 m2). Soil samples were taken from 0-30 and 30-80 cm in starting and ending points of each transect. Measured soil properties included gravel, texture, available moisture, saturation moisture, organic matter, lime, gypsum, pH and electrical conductivity. To analyze environmental data, classification (using TWINSPAN) and ordination (using PCA, CCA) were used. The results indicated that soil salinity, texture and available water play the main role in distribution of plant species.

This paper has focused on the application of hydro- geochemical techniques in conceptualizing of groundwater and to estimate recharge/discharge and the renewability of aquifer in Hashtgerd Watershed, Iran. At first, the aquifer boundary was defined based on data of existing wells and basin morphologic conditions. Estimation of recharge rate at different depth intervals by using tracer mass balance was done for 291 representative groundwater samples which includes 195 samples from soil and water of unsaturated zone in depths of 30 to 90 m (sampling in each meter), 10 samples were taken from rainfall, five samples from Qanats and 21 samples from wells and 60 samples taken from surface water in the study area. Based on water balance technique applying to a 7 year measured data and evaluation of hydrological and hydro- geological processes in the Watershed, average groundwater depletion was calculated at 0.37 m/year that indicated annual recharge rate of 245 million cubic meter (mcm) and over use of storage capacity of the aquifer. The groundwater studies showed that the natural recharge from direct rainfall is about 2% of total recharge. The annual recharge rate over an area of 752 km2 varies from 2.3 to 15.1 mm/yr. The required time for aquifer recharge from rainfall for the aquifer of 30 m thickness in the southern part of the aquifer is 1200 years while for aquifer of 90 m thickness in the north, recharge time is around 1100 years. On the other hand, in north and south of the aquifer, transitivity rates are 2500 and 300 m2/day, respectively with the groundwater renewability of 2.92 years which shows the importance of renewability of groundwater via concentrated/linear recharge from fractured zones. Studies of direct recharge in other parts of the world have shown that direct recharge rates may vary from zero to around 40% of mean rainfall volume. The results of this study revealed that around 98% of aquifer recharge occurs via concentrated/linear recharge from fractured zones with the average renewability of three years. Then it is recommended to consider the above mentioned geologic features in concentrated recharge of aquifer in saturated zone by watershed management, floodwater spreading and vegetation cover improvement projects.

In western and southern watersheds of Isfahan province, combinations of natural and human factors have caused numerous landslides related damages. One of the main strategies for restricting the damage caused by the landslide is to avoid these regions. For this purpose, it is necessary to prepare precise landslide hazard zonation map for such areas. For this purpose, by aerial photos, satellite images, geological maps and field studies, landslide inventory map was prepared in of the upstream watersheds of Karoon Basin called Marber River Basin with an area of 800 square kilometers. Then, nine factors including lithology, slope, land use, rainfall, vegetation cover, aspect, and lineaments elements such as road, fault and drainages were studied as 54 parameters. To enhance accuracy, speed and ease of analysis, all spatial and descriptive data were interred into GIS and 27466 homogeneous units were obtained by overlapping of the mentioned map layers. Analytical Hierarchy Process (AHP) and Multivariate Regression (MR) were used for multi criteria decision analysis and the results showed that both methods have the same accuracy in the separation of zones (lines) with the specific index of landslide risk.. But AHP approach of regression data, based on total quality index as an indicator of the accuracy of the learning has higher acceptability. This is related to this fact that the method has considered all 54 effective parameters due to the inherent performance of natural phenomena and events involved with the landslide. Based on multivariate regression method, only 30 of 54 variables were significant at 95% and 99% levels and r coefficient of regression equation was 57% which is quite acceptable

Sand dunes mobility is one of the serious problems in arid regions. Since wind regime is one of the important factors in sand dunes formation, its frequency, direction and magnitude can be effective. Amount of wind energy and its directional variability (wind regime) have significant control on the morphology and maintenance of aeolian landforms. By recognizing of morphometric and morphodynamic characteristics, it is possible to control soil erosion. Thus, statistical analysis of wind data using Tsoar index (sand dunes mobility index) in the study area was considered to understand wind regime role in volume and direction of transported sediments. Sand drift potential amount of the study area is 100.8 v.u. and sand flux is 2.358 m3/m.year resulted from Lettau – Lettau equation. Considering wind erosion power, the study area is in low class based on Fryberger & Dyne (1979) classification. In spring the wind blowing pattern has west direction and is different from other seasons. Also, the most frequency of blowing wind higher than threshold velocity occurs in this season. Unidirectional index value is 0.64 for this region that results formation of transverse dunes (barkhanoid).

Some contaminants associate with soil particles and, thus, their transport and fate in the environment is determined by the soil erosion processes. Eutrophication, low oxygen levels and high nutrient (nitrogen and phosphorus) concentrations in reservoirs, canals and other water courses, is a common water pollution feature. Phosphorus (P) is one of the major plant nutrients and also the major nutrients controlling eutrophication of surface water. P load pulsed by heavy rainfall may damage the ecological quality of downstream. The present study was conducted in Kojour Watershed located in Mazandaran province.The results showed that P loss varied from 0.26 gr lit-1 to 1860.64 gr lit-1. It also proved that P concentration could not estimated by flow discharge, while sediment concentration can estimate loss of P with determination coefficient and estimation error of 94% and 23%, respectively. The results could facilitate the application of given methods obtained in the present study to other ungauged watersheds with similar conditions and leading to the suitable soil and water management and planning.