نشریه مرتع و آبخیزداری
سال هفتاد و پنجم شماره 2 (تابستان 1401)

This study was conducted to evaluate the effect of polymer mulches and plant mulch on some soil physical properties. For this purpose, effects of synthetic polymer, natural polymer, natural - synthetic polymer, and litter, On some physical properties of soil at two depths (0-5 cm and 5-30 cm) and two time periods in a completely randomized design with four replications was studied. 10*10 meter experimental plots were considered and mulches covered 2 cm of the soil surface in each plot. The results showed that the use of mulches in the first week of applying, affected the bulk density (3.6% increase in synthetic polymer), porosity (6.01% increase in synthetic polymer), temperature (2.52% increase in litter and 1.85 decrease in natural polymer) and humidity (16.67% increase in synthetic polymer) at the layer of 0-5 cm, Soil moisture (16.67% increase in synthetic polymer) was also affected at the depth of 5-30 cm. Six months after the experiment began, mulches were applied, made a significant difference compared to control in the bulk density (4.81% and 2.12% decrease in synthetic polymer for 1st and 2nd layers respectively), porosity (8.23% increase in synthetic polymer for 1st layer and 4.12% increase in natural - synthetic polymer for 2nd layer) and moisture content of both surface and beneath soil (103.53% and 48.6% increase in natural - synthetic polymer for 1st and 2nd layers respectively), also the electrical conductivity of the first depth of soil (6.23% decrease in natural - synthetic polymer) was affected.

Precipitation plays an important role in climatic, water, energy and biogeochemical cycles. Several global and regional data sets currently provide historical estimates of this variable over Iran, including the MWEP and WFDEI forcing datasets and production of some institutions such as MOHC, SMHI and IITM. All these datasets provide data with different resolutions based on gage stations, satellite Images and models output. In this study, we do an inter comparison between these data sets during 1990- 2008. We also validate all ten data sets against independent ground station observations over 30 second-order basins of Iran. MSWEP and WFDEI have an acceptable compatibility with observational data on different spatial and temporal resolutions. RMSE and Bias are 5.68, 6.34 and 0.58, 2.75 for these two datasets during 228 months, respectively. However, it is needed that MSWEP improves in the western and northwestern parts of the country and WFDEI in June and September months. Our findings in this research provide valuable guidance for a variety of stakeholders, including rainfall- runoff and land-surface modelers, watershed management studies and data providers.

The influx of quicksand in the desert areas of Iran causes damage to various aspects of life of the inhabitants of these areas. Oil mulching is one of the measures that has been used for many years to stabilize quicksands. Because oil mulch is made up of heavy petroleum products, it can contaminate water resources in these areas with heavy elements and hydrocarbons by entering water sources. To investigate the effect of heavy elements and hydrocarbons on water resources, samples of oil mulch in short-term, medium-term and long-term periods from Hamidiyeh sands of Khuzestan province and also samples of oil mulch of Abadan refinery in laboratory conditions with Simulations of natural conditions and 24-hour residence time in contact with water were investigated. The results of this study showed that the amount of pollution of heavy metals other than elemental, which in the long-term, medium-term, short-term and control area increased by 95%, 115%, 123% and 129%, respectively, than the allowable limit. Oil mulch does not have a significant effect on increasing the pollution of water resources in terms of heavy elements. Examination of oil mulch on the amount of hydrocarbons in water showed that with the exception of Naphtalene and Benzo (g, h, i) Perylene, which decreased in the medium and short term compared to the control area, the difference of other hydrocarbons compared to the control area increased. Been; But in general, the amount of all hydrocarbons studied in the studied treatments was less than their allowable limit.

The SWAT model is widely used to simulate watersheds and evaluate the impact of conservation watershed management practices. In this model, the simulation of the watershed processes is based on hydrological response units (HRUs) which are created by overlaying land use /land cover, soil and slope maps. Meanwhile, in the HRUs definition steps, these units become conceptual and lose their spatial location and continuously. This approach is a useful and often inevitable way to simulate large and heterogeneous watersheds in terms of computational efficiency. However, if the aim is spatializing and evaluating the effectiveness of management methods on runoff, sediment and other pollutants in medium to small basins, it is necessary to know the exact location of HRUs. The purpose of conducting this study was present a new approach to defining spatial and independent HRUs and compare the simulation results based on this method with the standard form of the model. In the new approach, independent and spatial HRUs are defined through pre-processing procedures in GIS and uniquely named soil units. The model results of both approaches were very similar and no significant difference was observed in the model outputs in Taleghan watershed. The Nash-Sutcliffe coefficient of the simulated runoff and sediment at the outlet with the standard approach was 0.75 and 0.64, respectively. While, it was obtained 0.74 and 0.61, respectively for the new approach. The definition of spatial HRUs by applying the proposed method provides more tangible and practical outputs, which is more beneficial for identifying the critical areas as well as locating conservation practices compared to the conceptual HRUs approach.

The present research aims to assess climate change in the Minab plain and its effect on groundwater level variability in the future period. Climate change was explored by the climatic model CanESM2 using the SDSM4.2 software package, and the effect of climate change on groundwater resources was quantitatively modeled in the GMS10.0.5 software package under the emission scenarios of RCP2.6, RCP4.5, and RCP8.5. The results for the effect of climate change in the future period in the context of these scenarios showed that temperature will increase by 1.88ºC, 2.60ºC, and 4.28ºC and precipitation will decrease by 34.19%, 42.08%, and 59.43% versus the reference year, respectively. The results for the application of the climatic scenarios using the groundwater model revealed that due to the decline of precipitation in this period, mean groundwater level balance in the future periods leading to 2019, 2024, 2029, and 2035 versus the reference year (2003-2004) will be -13.99, -19.003, -22.70, and -25.61 m/yr in RCP2.6, -13.99, -18.95, -22.75, and -24.73 m/yr in RCP4.5, and -14.23, -19.22, -22.003, and -25.46 m/yr in RCP8.5, respectively. This shows that the drawdown will be being aggravated over time. Finally, this decline of precipitation and rise in temperature due to climate change and the subsequent increase in water abstraction for different uses will result in the growing depletion of the groundwater tables in Minab. So, it is recommended to planners and authorities to adopt strategies for adaptation to new climatic conditions and water scarcity and accommodate themselves with future conditions.

Good governance, by providing space for participatory processes, is a good platform for strengthening civil society alongside government and the private sector in governing countries. Meanwhile, NGOs, as an important part of civil society, are trying to fill government loopholes in geographical areas. In the discussion of non-governmental organizations, we can point to their importance as one of the key players for achieving good governance in the context of promoting social capital. The present study, which is a descriptive-comparative study, compares the components of good governance (with those of accountability, transparency, accountability and rule of law) by non-governmental organizations and local governments in Iran. The sample size of the study was 296 people (157 members of NGOs and 140 members of local government) who were selected through available sampling and snowball. The results showed that the NGOs have performed better than the local government in achieving the components of good governance. The components of good governance were significantly related to the control indicators of poverty, corruption, and the elimination of discrimination and inequality, which is a great goal to be achieved through the active performance of non-governmental organizations.

One of the integrated water resources management requirements based on participatory management planning is identification and analysis of key stakeholders. Identifying structural aspects of organizational stakeholder's network can be evaluated using social network analysis and their position and role for inter-organizational integration and coordination in water resources management can be determined. In this study, using social network analysis method, stakeholders related to participatory governance of Abhar plain water resources, including 20 organizational stakeholders were analyzed and policy indicators were evaluated at the level of the network of organizational stakeholders. Indices of density, size, reciprocity, transitivity, centralization and geodesic distance in network of relationships at the macro level, core-peripheral index in the middle scale and centrality indicators at the micro scale of network were examined. Rate of network density index is moderate and according to index of reciprocity, moderate amount of bilateral and reciprocal relations among organizational actors, cohesion and organizational capital are assessed as moderate. According to transitivity index, stability and balance of information exchange network is low. Analysis of core-periphery index of stakeholder's network shows a higher density of links and greater organizational cohesion among central organizations compared to peripheral subgroup and amount of information exchange between central and peripheral subgroups was evaluated as moderate. Based on centrality indicators, geometric position of each actor in network was determined. For decision-making, planning, policy-making and participatory governance of water resources in Abhar Plain, key and effective organizations and political forces, as well as organizations with low power and marginalized, were identified.

Ecotourism, as a side activity of rangeland, can be effective in improving the livelihood of rangers and will reduce the pressure on rangelands by economizing rangeland. In this study, with the aim of evaluating the potential rangelands of Dermian , for ecotourism use, based on environmental and ecological factors (climate, topography, soil, distance from water sources and vegetation attractions) and infrastructure (distance from the city and from roads), was done. From the combination of maps in the GIS environment and based on the FAO limiting factor approach,, the rangeland suitability was determined. Based on the results, 36.7% of rangelands are in the middle suitability category (S2), 46.5% in the low suitability category (S3) and 16.8% in the non-suitable category (N) in terms of ecotourism. In this regard, 61.5% of the rangelands for livestock grazing, have low suitability (S3) and 38.5%, unsuitable (N). The percentage of vegetation and,, the poor condition of soil erosion, are factors limiting the suitability for ecotourism and livestock grazing. , it is necessary to reduce the number of livestock and graze livestock in accordance with ecological principles; that used the rangeland of the region for ecotourism along with livestock. This, in addition to compensating for the economic problems, will also help restore vegetation. Due to the need to preserve rangeland,, forest parks can be created to accommodate tourists, up to a suitable radius of the desired rangelands, and by placing remote viewing platforms and sidewalks, from the amount of damage to vegetation and reduced soil degradation.

Unprincipled exploitation of water and soil resources, while increasing the likelihood of floods and increasing the rate of sedimentation, has reduced agricultural products and losses of national capital. Due to the destruction of Nakhab watershed in recent years, watershed management operations have been carried out in this watershed. The purpose of this study is to investigate the role of operations in runoff and soil erosion control. For this purpose, HEC-HMS model was used to determine the rate of reduction of flood peak discharge and MPSIAC model was used to determine the rate of erosion and sediment change in both cases before and after the operation. According to the results, the implementation of operations increased the flood peak time by 60 and 30 minutes and also reduced the peak discharge by 54% and 28% for the return period of 2 and 100 years, respectively. In addition, if the reservoir of structures is filled with sediments, they still have a significant effect on increasing the peak discharge time and reducing the volume and peak discharge of flood. The results of erosion and sedimentation show that due to the implementation of operations, special erosion has decreased from 10.18 to 9.8 tons per hectare per year and special sedimentation of the watershed from 3.16 to 2.9 tons per hectare per year. Since the watershed is a complex system, it is suggested that in order to achieve sustainable development, integrated management of all resources and the policy approach should be considered as an unavoidable necessity.

Climate change has been a serious issue in the last two decades, and many studies have focused on its various aspects. In the present study, the effect of climate change on the distribution of Bromus tomentellus was investigated. To do this, 19 bioclimatic variables and three physiographic variables and logistic regression model were used to quantify climate change in 2050 and to study its effects on the change of B.tomentellus species. First, using 17 synoptic stations in and near the province, a database of precipitation variables, night temperature, daily temperature and average temperature was formed and 19 climatic measures were calculated. Also using the digital model of height, with an accuracy of 30 meters; physiographic variables of slope, direction and height were prepared. Then, the presence and absence points of the species were determined and using logistic regression, its vegetative behavior was determined and the modeled map and related equations in the current conditions were calculated. Using current equations and inserting data extracted from the Worldclime database; the future distribution map for 2050 was generated under RCP4.5 and RCP8.5 climate scenarios. The results showed; the average annual temperature (BIO1), the annual temperature range (BIO7) and the average temperature of the coldest season (BIO11) are the most important for habitat fit, the values of which increase with increasing climatic conditions. Average annual temperature in places with a probability of more than 75%; over the next three decades, it will rise by 1.6 to 1.2 degrees Celsius.