جستجوی مقالات مرتبط با کلیدواژه « سمنان » در نشریات گروه « آبخیزداری، بیابان، محیط زیست، مرتع »

With the rapid development of society, economy and population growth, the impact of human activities on ecosystems is increasing, which has caused the relationship between human well-being and ecosystem to be in the spotlight. To that end, ecosystem services as an essential element for human development and survival emphasizes the benefits that natural ecosystems provide to humans. These services are divided into four categories based on the Millennium Ecosystem Assessment (MEA): provision, regulation, support and cultural. Cultural ecosystem services are important component of ecosystem services that refer to intangible benefits of the human beings from ecosystems and play an essential role in enhancing human well-being. Cultural ecosystem services can include the use of natural resources directly or indirectly.

The present study was conducted with the aim of modeling recreation services in Semnan province. For this purpose, the integration of the analytic hierarchy process (AHP) of one as the multicriteria decision-making methods and the recreation opportunity spectrum (ROS) model was used. In the ROS model, recreational service is estimated based on recreation potential index and accessibility- remoteness index. In the recreation potential index, three elements: the degree of naturalness, the protected regions, and the attractiveness of water bodies, and in the accessibility- remoteness index, the distance from roads and human-made areas were mapped. In this research, Sentinel-2 satellite images were used to prepare the land use map of 2021. Then, using the maximum likelihood algorithm, land use maps were prepared in 18 classes.

According to the land use map, pastures, barren lands and rainfed agriculture have the highest levels of land use in the studied area with 23.57, 22.27 and 17.31% respectively. After that, waterbodies, salt marshes and irrigated agriculture are the dominant land uses with 15.65, 10.98 and 7.84%, respectively. It is worth mentioning that the smallest area of the region is dedicated to wetlands and urban uses. Based on the results, Forest and pasture areas have the highest potential in providing recreation services in the study area. It was also seen that, the third category (low provision- difficult access) and the seventh category (high provision- easy access) respectively have the highest and lowest land surface coverage in terms of the provision of recreational ecosystem services in the province. Overall, the results showed that recreation ecosystem service is affected by various factors caused by human development, especially land cover/use changes. Considering the concentration of both variables of ecosystem service provision and urban and industrial development in the northern half of the province, it is vital to pay attention to the conflicts between the development and management of ecosystem services. If this is ignored, in addition to intensifying the instability of development, the destruction of natural assets of the province, especially forests and pastures, which are the main source of provision of various ecosystem services such as recreation, will intensify.

In general, the results indicate that most of the places in the province have a medium to low ability to provide recreation services. Considering that recreational potential is important for the well-being of urban populations, increasing urban parks and green infrastructure areas is a useful way to improve the quality of the recreational experience. Therefore, urban development strategies should increasingly aim to strengthen the natural and artificial network of green space, diversity of plant compositions and biomass structure, and proper management of green space. This is necessary for the design of green space with regard to maximizing ecosystem services in Semnan province.

Gully erosion is one of the factors threatening the environmental balance and its stability and plays a prominent role in increasing the sedimentation capacity of watersheds and changing the hydrological characteristics of surface streams. The purpose of this research is to evaluate the effectiveness of the maximum disorder machine learning model in order to prepare a gully erosion sensitivity map in the Semnan watershed. Identifying the most important environmental factors affecting the occurrence of gully erosion using the jackknife method and examining the importance of each environmental factor in the study area by analyzing the response curves are other goals of this research.

This research consist of five main steps: the first step is choosing the study area, collecting and preparing maps of the effective factors, the second step is preparing the distribution map of the ditch erosion event, the third step is the multiple collinearity test with the index of the tolerance coefficient and the variance inflation factor in order to check the information overlap of the effective factors. and checking the importance of the factors, the fourth step is to implement the maximum irregularity or maximum irregularity model, prepare a zoning map of sensitivity to the event of gully erosion and classify it into five categories: very low, low, medium, high and very high, the fifth step is to evaluate the classification accuracy and validate the zoning map and Prediction of sensitivity to gully erosion.

According to the results, among the 23 initial factors or variables, the factors of the waterway slope length index, surface curvature, and waterway power index had colinearity or overlapping information, and in the next stages, they were removed from entering the modeling process, and modeling was carried out with 20 independent factors or variables. The gully erosion sensitivity map of the studied area showed that the southern and southern parts of the Semnan watershed are prone to gully erosion. Also, the zoning results obtained from the implementation of the maximum irregularity model indicate that the areas prone to gully erosion are in high areas, sensitive rock units (quaternary clay and marl zones), average annual rainfall, Eridesville soil type, ultra-arid climate, high drainage density classes, low slope, low lands without geographical slope, high topographic moisture index, pasture land use and low land surface texture are observed. Also, the maximum irregularity model has 91% and 89% accuracy in the calibration and validation stages, respectively, which in terms of efficiency is in the very good category for predicting gully erosion prone areas.

About 35% of the area of high and very high sensitivity areas resulting from the implementation of the maximum irregularity model include more than 90% of the ditches in the region. Also, the maximum irregularity model in the stages of implementation or development and prediction or validation with the area under the receiver operating characteristic curve with the values of 0.91 and 0.89, respectively, is effective in zoning and predicting the occurrence of gully erosion. This result will be useful for local managers and planners as well as executive experts in order to identify areas prone to gully erosion and determine the best implementation methods of watershed operations for soil protection approaches.

The sustainability of soil, especially in fragile ecosystems, is an indispensable indicator of sustainable land management that depends on the physical, chemical and biological properties of the soil. In order to study the soil sustainability in Semnan desert region of farms, gardens and rangelands as arenas located on an educational farm with different irrigation administrations, the Sustainability Index (SI) and the Cumulative Ranting (CR9 &CR11) were used. Exploring the crust and sampling of surface and subsurface horizons of selected areas and measuring 12 important and effective characteristics of soil physical properties, the indices were calculated in each area and the effects of different types of land use on soil stability were investigated. The results showed that the SI in the surface layer of arable land due to the impact of cultivation and the positive role of organic matter was above one, and in the rest of the land was less than one which indicating the instability of the soil. According to the CR results, surface and subsurface layers of soil were not found in very stable and stable classes in the studied lands. The CR results also showed that the stability soil in the multi cultivates farm is a better condition, it may be due to its positive role in increasing soil correction factors compared to other lands. Correlation analysis of the indices showed that soil organic carbon, structural index, electrical conductivity, sodium adsorption ratio and mean weight diameter have a direct and more effective impact on soil sustainability.

A significant area of the country's rangelands is degraded due to various factors and an important part of rangeland species is endangered or their population is severely reduced. Rangeland improvement and reclamation through selecting suitable species and finding the best cultivation methods are of utmost importance in these rangelands. Therefore, according to the results of the research project performed in the Research Institute of Forests and Rangelands, the seeds of Sa.arbuscula were collected from different rangelands of Semnan province along with the existing populations. The study was conducted in a randomized complete block design with three replications at Semnan Research Station since 2011 for five years. The data were analyzed using SAS software and the means were compared with Duncan's test. Our results clearly showed that among the study accessions of Sa. arbuscular, the genotypes 230 and 234 with an establishment percentage of 86.67% and 84.02% were superior, respectively. Therefore, the genotypes 230 and 234 could be recommended for rangeland improvement and reclamation.

The use of saline and lands low-yield lands for forage production is an important step towards optimal utilization of low quality soil and water resources and supplying livestock forage as well as conservation of soil and water resources. Therefore, this research was aimed to investigate the establishment potential, canopy cover percentage, height growth and yield. Garmasar Desert Research Station with a soil salinity of 30-35 ds/m and Atriplex canescens, Atriplex leucoclada, Atriplex verrocifera, Aeluropus lagopoides and Aeluropus littoralis were selected and the species were cultivated in three replications. In each replication, 15 individuals of the study species were cultivated on each row. According to the results, the establishment percentage of At. ca, At. le, At. ve, Ae. la and Ae. li was recorded to be 95.5%, 95.5%, 100%, 97.7%, and 100%, respectively, indicating high establishment potential. The results of analysis of variance for annual yield showed that all the study species were able to produce forage in saline lands with a soil salinity of 35 ds/m.Among the study species, At. ca and At. le had the highest canopy cover and height. The highest forage production (more than 2 kg ha-1) was recorded for At. le, compared with other study species.Our results clearly showed that yield and canopy cover superior to other traits in showing the differences among the study species.

The 21st century will face the controversial debate on sustainable development with the priority of sustainable urban development. Urban planning has not paid enough attention to the sustainability of cities dependent on natural resources. The development of the city without regard to its watershed makes no sense. Urban strategies have focused on the implementation of static plans, followed by the modernist school, and the need for the interconnection, sustainability, and vitality of urban watersheds, which are the city's feeding vessels, has not been addressed. This research was conducted with the main purpose of explaining the sustainable development strategies of Garmsar city based on integrated management of urban watershed by understanding the factors affecting the stability of the watershed and analyzing the causal relationships of urban sustainability in the operation with Halbehrood watershed stability factors. The research method is descriptive-analytical and collecting the information required for research through library studies and field observations. In order to analyze the information, the DPSIR environmental evaluation model, the AHP model and the SWOT model have been run integrated to determine the best sustainable development strategies of the Garmsar city. The results of the studies showed that Garmsar city is not sustainable as a city dependent on urban watershed and it is not sustainable in terms of providing necessary resources of the basin, but the sustainability of the watershed and the Garmsar city is possible through the implementation of Strategies appropriate to existing resources. Based on the results of quantitative and analytical matrix analysis, eight of the main identified strategies were prioritized. Among them, the development of a joint program for water, agriculture and natural resources in order to explain the effective measures of the chain of production, distribution, and use of water in the upstream lands is the first priority.

One of the conventional methods in identifying issues or making decisions in communities is considering the views of individuals of the community. The aim of this research is to determine the effective determinants of rangeland performance according to the views of range manager community in winter pastures of the Semnan province. Analytical Hierarchy Process (AHP) as a multi-criteria/quantitative approach was employed for this research. Firstly, determinants of rangeland performance were grouped into human (economic and social) and natural (topographic conditions, climatology, geology and soils) criteria. Then, the major sub-criteria were identified based on interviews, existing experiences and literature review. Pairwise Comparison of all identified criteria and sub-criteria were conducted based on semi-structured questionnaire and interviews with 30 range managers. Finally, analysis of questionnaires was carried out using AHP method within Expert choice software. According to results, season, precipitation and private ownership seem to be the most important factors, respectively. However, research community had more disagreements regarding the natural criteria compared to human ones.

At this research, the effect of the grazing intensity on the features of the soil seed bank in shrub lands in arid zones in Semnan province was studied. The sampling area (500 hectares) was determined including no-grazing area (un-grazed 15 years), the moderate grazing intensity and the high grazing intensity area near the close of interval each other. In each treatment of soil sampling, systematic sampling was done within the 20 plots of 1 × 1 m intervals along 4 transect of 50 meters and a length of 200 m. Soil samples from each plot at depths of 0-5 and 5-10 cm and radius 3 cm was done by Auger. In each treatment, a total of 20 samples and finally 60 soil samples were collected and transferred to the greenhouse environment. Soil samples were planted with dimensions of 40 x 40 cm sieve containers. After finishing the greenhouse cultivation, seed density per unit area in terms of number of species per square meter was calculated. Considering the density of seeds per square meter, the ratio of frequency of each species to all species was calculated. One-way ANOVA was used to compare the data. Independent student t -test used to compare characteristics of the seed bank was also studied in tow depths. Results show a significant effect because the intensity and depth of seeding is. Both moderate and heavy grazing treatments were created impact on soil seed bank density per unit area. The highest and lowest seed density fluctuations due to the increased depth of the treatments no-grazing (43.5%) and heavy grazing (21.9%) was estimated. The average grazing intensity not changes significantly in the soil seed bank diversity than Un-grazed areas in different layers. But in the heavy grazing, soil seed bank diversity was significantly decreased in the first depth (39.5%) and the second depth (51%).

This study investigates monthly and seasonal variations of carbon emission from the soil at different grazing intensities. Three areas of exclosure، low and high grazing intensities were selected in Ghoosheh region of Semnan province. Carbon emission was measured monthly، in each treatment applying alkali traps (CSC) during a year. Emission and grazing data were analyzed، using a factorial experiment in a completely randomized design with four replications. To investigate the relation of soil moisture and air temperature with carbon emissions in each area، Pearson correlation was used. Results showed that the emission levels under different grazing intensities had significant difference. The highest emission occurred in high grazing intensity، in August (3. 34 g C m-2 day-1) and lowest in February (0. 033 g C m-2 day-1) in exclosure. The seasonal distribution of emission showed the highest amount، in summer، autumn، winter and spring respectively. There was also a negative correlation between carbon emissions and soil moisture.

In this research, two small sub-basins were selected in Darjazin Watershed of Semnan to evaluate the effect of ruck check dams on peak and volume of flood in small watersheds. Two watersheds were chosen as study area in a part of southern Alborz Mountain with arid and semi-arid climate. These watersheds are located in upland of Mahdishahr city and many check dams are constructed for flood control in past few years. All check dams were examined during field operation and their sedimentation were assessed. Results showed that all check dam reservoirs were filled by sediment. In this research, the peak and volume of floods were assessed in three scenarios of 1) watersheds with no check dams 2) watersheds with empty of sediment check dam reservoirs and 3) watersheds with full of sediment check dam reservoirs. HEC-HMS model was used for rainfall-runoff simulation.. Mean comparison test by paired method for all three scenarios showed that flood peak and volume have significant difference at α=1% level. But, flood peak and volume in scenario 2 are computed less than that of scenario 1 and in scenario 3 are computed more than that of scenario 2. On the other hand, flood peak and volume in the scenario 3 slightly decreased by 4.8 and 5.7 percent respectively compared to scenario 1 where is not significant based on the objectives of project.

Soil is considered as the most important natural resources of each country. Soil erosion is a serious hazard to human life. Soil erosion not only causes destruction of soil، but also causes much detrimental effects with sediments deposited in waterways، reservoirs and dams which reduce their storage capacity. These sediments، due to their physical and chemical characteristics have the highest erodibility. In this study، the physicochemical properties of marl units on soil erosion have been determined on 31 samples in marl lithologic units based on erosion shapes and thru dominant slopes. Soil physical and chemical properties were determined by standard analytical methods. Analysis of variance and comparing of means was performed. Finally، the factor analysis was used to separate the affording factors on erosion shapes. Erosion increased with increasing SAR، EC، Na، Cl، SO4، silt and clay and decreased with increasing in HCO3، TNV and gravel. EC، SAR، Na، Cl، TNV، HCO3، SO4، gravel، silt and clay have statistically significant difference between erosion types and factor analysis showed that EC، SAR، Na، Cl، silt and clay booster and HCO3، TNV and gravel are halter factors of erosion.

Due to diversity، high frequency and transportation as suspended materials، clay minerals can be used as sediment source indicators in drainage basins. In this study، clay minerals were used in Amrovan and Atary catchments، Semnan Province، Iran. To identify clay minerals، X-ray diffraction analyses were used. By performing four different treatments on the samples (K، KT، MG، MGG)، the respective graphs were obtained. To determine the percentage of each clay mineral، the area-under-a-curve method was used. Finally، the potential of each clay mineral in differentiation of sediment sources was determined using Kruskal-Wallis and Discrimination Function Analysis (DFA) statistical tests. The results of the Kruskal-Wallis test showed that all characteristics were below critical probable amounts، and، therefore، are suitable for differentiating sediment sources. Smectite is a clay mineral with the highest differentiation ability. It correctly classified 57. 5 % and 62 % of samples in the Amrovan and Atary Catchments، respectively. The results also showed that the combination of source indicator characteristics increases the differentiation ability of the characteristics up to 72. 5 % in the Amrovan catchment and 76 % in the Atary catchment.

In order to find some phenological phenomena of Atriplex griffithii with climate properties such as as temperature and precipitation, this study was carried out in the north-east of Semnan province from 2001 to 2004. In this survey, 10 Atriplex griffithii were selected and marked. Phonological stages (germination, vegetative, flowering, seeding, and regrowth) were measured in 15-day periods while reproductive traits were measured in 7-10 day intervals. Analysis of climatic data and recorded phonological stages showed that the growth of Atriplex griffithii varied with the fluctuations of drought and temperature in different seasons and two distinctive stages (vegetative and seeding) were recognized for each year. The first growth stage started from late winter and continued to mid-August and the second growth stage started from second half of August and ended in second half of December. Flowering started from May and seeds matured in June. Phonological stages also differed among geographical directions due to differences in rainfall, temperature and evaporation rate as flowering and seeding stages in southern slopes occurred in May and June and in northern slopes were in October and November, respectively. Obtained results can help range managers to set a time calendar for livestock entry and exit and also grazing season.

Considering the overuse of the aquifers and flow regime of ephemeral rivers of the country، performing artificial recharge projects in these rivers is necessary. Although، there have been a considerable number of researches in the artificial recharge system، there has been no method for determining the recharge efficiency of the artificial recharge systems on ephemeral rivers yet. The goal of this research is to determinethe recharge efficiency of the artificial recharge systems by using the flood flows of ephemeral rivers. In the suggested method، the first step is dividing the flood hydrographs of different return periods using model between different parts of the system. So the intake efficiency of ponds is determined. Then، accordingto the dimensions of recharge ponds and the penetrated water during the flood، the amount of water that can be recharged may be determined using seepage formula. For determining the river bed infiltration، a combination of hydraulic modeling using Hec-Ras simulation and Etcheveri method has been used. Finally، after determining the recharge efficiency of system for different return periods of flood، the total recharge efficiency of the system is determined by calculating the expected value. The suggested methodis applied for the artificial recharge system of Emamzade Abdollah River of Semnan، in center of Iran. The results show that the presented method has a suitable recharge efficiency and is able to use %81 flood flow for artificial recharge

Regeneration of black saxual (Haloxylon aphyllum) is an important project for sand dune fixation in desert area of Iran. Success of this project is largely depending on climate conditions and soil physical properties. In order to determine some inhibitor factors of black saxual growth, a project were conducted in a 2 ha black saxual site in Semnan, Iran. Morphological traits as: plant height, canopy cover, collar diameter and collar first sympodial interval and growth index were recorded on 5 year old shrubs. At the mean time soil properties as: EC, pH, SP and Texture (silt, clay, sand), were measured. The relationships among plant growth indices and soil properties showed a negative correlation (P0.05) between growth index and saturation percent (SP). It was concluded that SP factor was the most important factor to inhibit black saxual growth in Semnan province, Iran.