Mahshid Souri; MIna Bayat; Saeedeh Nateghi
Volume 32, Issue 2 , July 2025, Pages 109-123
Abstract
Background and objectives:Poor establishment of seeds, especially in arid and semi-arid areas, reduces the performance of rangeland plants, increasing the speed of germination and establishment of seedlings can cause them to absorb water and nutrients more quickly. The priming treatment shortens the ...
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Background and objectives:Poor establishment of seeds, especially in arid and semi-arid areas, reduces the performance of rangeland plants, increasing the speed of germination and establishment of seedlings can cause them to absorb water and nutrients more quickly. The priming treatment shortens the planting time until greening, protects the seeds and greens uniformly, which ultimately leads to uniform establishment and improved yield in the product. The aim of this research is to introduce the most effective priming on germination, height, yield, root and stem weight of Astragalus squarrosus Bunge species.Methodology:In this research, the effect of hydropriming, osmopriming and hormone priming on factors of germination, height, yield, root and stem weight of Astragalus squarrosus Bunge was investigated. The seeds of three ecotypes of Yazd, Semnan and Kashan were primed separately under hydropriming (distilled water), hormone priming (gibberellic acid 500 ppm) and osmopriming polyethylene glycol 6000 at two levels (-0.4 and -0.8 MPa). The statistical analysis of experiment was carried out in SPSS software at the form of a factorial design by applying two factors (priming treatment and drought stress treatment) on the collected seeds of three populations from three regions, Astragalus squarrosus Bunge species in the greenhouse.Results: Examining the results showed the significance of the priming effect on the indices of germination percentage, yield, height, root and stem weight of Astragalus squarrosus Bunge at the error level of 1%. The investigated characteristics of the seeds that were exposed to different types of priming were significantly different from each other compared to the control seeds. According to the results, the highest plant height (40 cm) and fodder yield (42 g/m2), germination percentage (38.7 percent), root weight (37 g) and stem weight (42.8 g) in ecotype Yazd using hydropriming treatment and under drought stress has reached 75% of the farm capacity, the second place was observed in osmopriming (polyethylene glycol) treatment. The results of this research showed that the best performance and result for planting Astragalus squarrosus Bunge in the direction of reviving degraded dry rangelands is hydropriming (distilled water) along with seed scraping.Conclusion: Based on the results obtained from this research and also, considering the fact that hydropriming is much cheaper and simpler than osmopriming and hormone priming, therefore, hydropriming is introduced as a treatment to improve the performance of nether species. This issue can be taken into the attention of rangeland operators and experts in improving the function and performance of this type of valuable local fodder.
Majid Kazemzadeh; Zahra Nouri; Majid Rahmani; Asghar Bayat; Salma Saedi Farkoush
Volume 32, Issue 2 , July 2025, Pages 124-139
Abstract
Background and objective: In recent years, extensive watershed management measures including biological, mechanical and biomechanical measures have been carried out with the aim of flood, erosion and sediment control and water storage in the different sections of research, study and implementation ...
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Background and objective: In recent years, extensive watershed management measures including biological, mechanical and biomechanical measures have been carried out with the aim of flood, erosion and sediment control and water storage in the different sections of research, study and implementation in the country. Evaluation of watershed management plans in order to analyze the performance of implemented watershed management measures and develop basic solutions is one of the basic needs in watershed management. Therefore, the aim of this research is to quantitatively and qualitatively evaluate the effects of biological and biomechanical measures of watershed management on the vegetation cover changes in Azimieh watershed, Karaj, Alborz province.Materials and methodsIn this study, vegetation changes were determined using Landsat series 5, 7 and 8, satellite images, and NDVI index in a period of 20 years (2000-2019). Then, by using the polytrend model, the trend of linear and non-linear changes and the effect of water management measures implemented in the watershed on the vegetation cover in the Azimieh Karaj watershed, Alborz province, were investigated. Also, in order to evaluate the accuracy of the results and satellite images, field measurements were also used. Also, in order to investigate the effect of climatic factors on vegetation changes, drought index and rainfall data of Karaj station were used.ResultsResults of trend showed that 41.9% of changes were significant over 20 years. 88.3% of the significant changes in vegetation were increasing. The results of Polytrend method showed that the changes in vegetation were cubic, linear and quadratic with values of 63.4%, 27.8% and 8.8%, respectively. Evaluation of the effects of implemented measures to improving the vegetation status of the watershed showed that the percentage of canopy in the watershed was on average 28% before implementing the watershed management measures, which has increased to 34% after the implementation of watershed management measures. Of the total area of biological operations in Azimiyeh watershed (2724 hectares), in 70% of the area, changes in the vegetation status of the rangeland have been nonlinear and these changes were in projects such as seeding and tree planting and terrace. Also, the vegetation in a parts of the downstream areas of Azimiyeh watershed have been destroyed by non-linear trends due to the growth and development of residential areas and civil works such as the construction of Hemmat Highway.ConclusionThe performance evaluation of watershed management projects in Azimieh Karaj watershed showed that watershed management measures have caused a significant increase in vegetation in the region. On the other hand, development and urbanization in the downstream areas of the watershed has caused the loss and destruction of vegetation over the past years. The evaluation of watershed management plans can show the positive and negative results of the measures implemented over the years, and in this way, steps can be taken to solve their obstacles and problems.
Masoud Safari; Marzban Faramarzi; REza Omidpour; Hassan Fathizad
Volume 32, Issue 2 , July 2025, Pages 140-159
Abstract
Background and ObjectiveVegetation cover and aboveground biomass are critical components of arid and semi-arid ecosystems, playing a vital role in environmental sustainability, carbon sequestration, biodiversity conservation, and providing forage for both domestic and wild herbivores. Due to their high ...
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Background and ObjectiveVegetation cover and aboveground biomass are critical components of arid and semi-arid ecosystems, playing a vital role in environmental sustainability, carbon sequestration, biodiversity conservation, and providing forage for both domestic and wild herbivores. Due to their high sensitivity to environmental changes, these regions require accurate and continuous monitoring. In recent decades, the use of vegetation indices derived from remote sensing data has emerged as a promising approach for modeling vegetation cover and biomass in natural resource management. However, these indices have been less thoroughly evaluated in arid and semi-arid areas. This study aims to assess the efficiency of Landsat 8 and Sentinel-2 satellite imagery and various vegetation indices in modeling vegetation cover and aboveground biomass in the arid rangelands of western Iran, using linear regression methods.Materials and MethodsThis study was conducted in the arid rangelands of Ilam Province, western Iran. Field data were collected using a random-systematic sampling method across 50 plots (30 × 30 meters) during the peak growing season and prior to livestock grazing. In each plot, the percentage of live vegetation cover, litter, bare soil, and gravel was recorded. Aboveground biomass was measured by clipping vegetation at ground level and weighing the oven-dried samples. Satellite images from Landsat 8 and Sentinel-2, corresponding to the same period as the field sampling, were acquired. Both slope-based vegetation indices, such as NDVI and EVI, and distance-based indices, such as MSAVI and SAVI, were extracted using ENVI and ArcGIS software. Linear regression analysis was employed to model vegetation cover and aboveground biomass. The performance of the selected indices was evaluated using the coefficient of determination (R²) and root mean square error (RMSE).ResultsThe results indicated that distance-based vegetation indices, such as MSAVI, outperformed slope-based indices in modeling vegetation cover and aboveground biomass. The MSAVI index derived from Landsat imagery provided the highest accuracy, with an R² of 0.19 for vegetation cover and 0.21 for biomass. Linear regression modeling showed that vegetation cover in the study area ranged from 5% to 81%. Additionally, the estimated aboveground biomass ranged from 6.8 to 58.4 grams per square meter (gm²). According to the results, when using slope-based indices such as NDVI, Sentinel-2 imagery yielded more accurate vegetation cover modeling compared to Landsat imagery. However, when distance-based indices were applied, Landsat imagery delivered significantly higher accuracy, while the accuracy of Sentinel-2 images decreased relative to their performance with slope-based indices.ConclusionThe results of this study indicated that the accuracy of vegetation cover modeling is influenced by both the types of indices used and the spatial resolution of satellite data. For slope-based indices like the Normalized Difference Vegetation Index (NDVI), Sentinel imagery demonstrated higher accuracy than Landsat for estimating vegetation cover. Conversely, for distance-based indices, Landsat imagery provided better accuracy, while the precision of Sentinel imagery decreased under these conditions. These findings emphasize the importance of selecting appropriate spectral indices tailored to specific regional characteristics, as this choice can significantly impact modeling accuracy. Furthermore, the results highlight that in arid regions, distance-based indices may be more effective, as they mitigate the impact of bare soil reflectance and provide more reliable information about vegetation cover. This research offers a foundation for optimizing remote sensing methodologies in future studies.
Maryam Naeimi; Adel Jalili; Samira Zadifar
Volume 32, Issue 2 , July 2025, Pages 160-184
Abstract
Background and objectivesGroundwater resources can be collected through wells, tunnels, and drainage paths; or inherently percolate to the surface through seepage or springs. It is consumed for drinking, agriculture, industry, environment, and ecosystems (Asadi et al., 2023). Management of underground ...
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Background and objectivesGroundwater resources can be collected through wells, tunnels, and drainage paths; or inherently percolate to the surface through seepage or springs. It is consumed for drinking, agriculture, industry, environment, and ecosystems (Asadi et al., 2023). Management of underground water resources is particularly important in arid and semi-arid regions, due to surface water is scarce. Hence, the dependence upon groundwater is quite remarkable. Evidence shows that factors including population growth and climate change play a crucial role in the intensification of groundwater levels (Hall et al., 2008).Lack of proper knowledge and excessive exploitation of underground water resources, irreparable damages such as a sharp and irreversible drop in the underground water level, reduction of the flow rate of wells and canals, changes in the pattern of underground water flow such as the advance of waterfronts. It has followed the saltiness and interference of salty waters. Therefore, in this research, the quantitative characteristics of underground water in the central desert watershed during the statistical period of 2001-2002 to 2017-2018 have been evaluated.Research MethodologyThe drainage basin of the central desert is a part of the great section of central Iran, which includes important cities such as Garmsar, Semnan, Damghan, Shahrood, Neishabor, Mashhad, Sabzevar, and Kashmer, creates an area of 226,523 Km2 between the south of Alborz and the northeast of Zagros. Considering the necessity of studies on the factors affecting the decline of the water level of groundwater resources, including hydrogeological droughts and human interventions, along with behavioral assessment; it is essential to provide appropriate protection and management solutions for groundwater resources.Hence, in the present study, various time lapse-year aligned maps, representative hydrographs of the study area, the average annual changes in precipitation and groundwater drought index (GRI), and the level of exploitation of groundwater resources for the target plain were calculated. To evaluate the quantitative status of underground water, the water level and the observation wells data in the aquifers of the study areas of the Central Desert watershed were used in the mentioned statistical period. In the following zoning maps, variations of underground water level fluctuations, aquifer storage volume, and drought conditions were analyzed. It is necessary to note that all the maps were drawn using Arc GIS and kriging tools.Results The results at the level of the central desert watershed, based on the updated statistics up to the water year 2019-2020, indicate the number of 29,360 underground water sources (wells, springs, and aqueducts) with the volume of discharge and withdrawal of 3659 million cubic meters per year. The number of springs, aqueducts, and deep and semi-deep wells is about 19, 21, 39, and 21% respectively in terms of number and terms of discharge about 9, 16, 72, and 3% of the total number and discharge of underground water sources.An annual survey of the number of groundwater resources in the study areas shows that the trend of deep wells increased until 2011 and then decreased. Increasing the number of wells can increase the exploitation of groundwater levels, and unprincipled management in the exploitation of groundwater resources for agricultural development causes a drop in water levels and a decrease in the qualitative value of groundwater resources, and subsequently turns dry areas into critical centers of wind erosion (Nasirian et al., 2018).In general, in most of the study areas, the rate of discharge from wells is much higher than that of springs and qanat. Therefore, the dominant system of groundwater exploitation is deep wells. Groundwater extraction by deep wells has increased significantly in different years, while its consequences could be seen as a direct impact on the existence of qanats, springs, and their average water supply. On the other hand, a decreasing trend in deep wells could be due to excessive extraction in previous years and well-greening events in the study area. Previously, excessive extraction of groundwater resources in the plains of the central desert such as Neyshabur (Rokni et al., 2016) and its consequences such as a water level depletion (4.8 meters in the ten years 1996- 2006), land subsidence, and a decline in water quality have been mentioned.Also, the most water level changes have occurred in the Rashtkhar, Ivanki, and Kashmar areas, which have a deficit of -29.30, -25.50, and -18.40 meters, respectively. The annual and cumulative changes in the storage volume of the reservoir in the Central Desert watershed area during the statistical period of 1998 to 2018 show that the volume of the reservoir has decreased by 25317 MCM. The continuation of the changes in the GRI shows that the first drought occurred in 2019, while the general trend of the GRI value was decreasing.ConclusionsGenerally, in most of the study areas of the central desert integration area, the amount of discharge from wells is far more than from springs and qanats. Therefore, the dominant system of using underground water is in the form of deep and semi-deep wells. Additionally, the results indicate the unsustainable use of water to maintain and expand human activities in the largest area of Iran, located in the arid/semi-arid sector. If not controlled, such excessive use of underground water can cause environmental problems and serious socio-economic consequences. Finally, due to the unpredictability of climatic droughts and the impossibility of preventing them, it is necessary to reduce their negative effects by planning and applying proper management of underground water resources.
nassim shabani; Mostafa Tarkesh Esfahani; Alireza Rajabi Mazhar; Nafiseh Salahi Moghadam; Peyman Akbarzadeh; Hasan Shadman; Mehdi Khoshbakht
Volume 32, Issue 2 , July 2025, Pages 185-200
Abstract
Background and ObjectiveClimate change is recognized as one of the serious threats to biodiversity in natural ecosystems, having major impacts on the survival, performance, and distribution of plant and animal species. These changes can lead to alterations in population rates, species extinction, and ...
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Background and ObjectiveClimate change is recognized as one of the serious threats to biodiversity in natural ecosystems, having major impacts on the survival, performance, and distribution of plant and animal species. These changes can lead to alterations in population rates, species extinction, and shifts in the distribution of plant habitats. Therefore, a precise understanding of the climatic niche of species and the prediction of their responses to climate change are essential for natural resource management. Species distribution models (SDMs) are useful tools for predicting habitat changes and assessing the future impacts of climate change. In this study, the performance of three species distribution models, including the Maximum Entropy Model (Maxent), Ecological Niche Factor Analysis (ENFA), and Non-Parametric Multiplicative Regression (NPMR), is compared. The effect of climate change on the distribution of the habitat of Astragalus adscendens is analyzed for the years 2050 and 2100 under the HadGEM-RCP 4.5 scenario using the best-performing model. Materials and MethodsIsfahan Province, covering an area of over 107,000 square kilometers, has a wide range of elevations (707 meters to about 4000 meters) and diverse climatic zones (semi-arid, steppe, semi-steppe, dry forests, and high mountains). The plant species Astragalus adscendens is recognized as a native and significant species of the Iranian rangelands. To model the distribution of this species, 70 presence sites and 70 absence sites were randomly extracted from the vegetation type map of Isfahan Province using a stratified sampling method (Feizi et al., 2017). Additionally, 70 new sites were sampled through field visits in the towns of Semirom and Fereydunshahr using a GPS device for model evaluation data. A total of 22 environmental layers were prepared, including three physiographic variables (slope, aspect, and elevation) and nineteen bioclimatic variables for the present, 2050, and 2100 under the RCP 4.5 climate scenario using the HadGEM2 general circulation model. These variables are derived from three main parameters: monthly precipitation, minimum monthly temperature, and maximum monthly temperature. All environmental layers were prepared with a pixel size of one square kilometer. Finally, three modeling methods Maxent, ENFA and NPMR—were used to predict the distribution of Astragalus adscendens. ResultsAll three models showed good performance for predicting the habitat of Astragalus adscendens (AUC > 0.85). A reduction in habitat area under the HadGEM-RCP 4.5 climate change scenario is evident in all three models. Annual precipitation was identified as the most significant environmental factor influencing the distribution of Astragalus adscendens. Species response curves for the environmental variables, extracted from the Maxent and NPMR models, suggest that Astragalus adscendens is more prevalent in areas with precipitation over 350 mm and elevations above 2500 meters. The response curve of the species to slope indicates a positive relationship, showing that the likelihood of species presence increases with slope. Based on model evaluation, the Maxent model outperforms the others, showing a higher AUC index. ConclusionClimate change, particularly reduced precipitation and increased temperatures, will have significant negative effects on the distribution of Astragalus adscendens, such that by 2100, the presence of this species in Isfahan Province, especially in the Fereydunshahr region (western part of the province), will severely decrease. It will only be found in patches in the high elevations of Padanah in the Semirom region. It should be noted that the species distribution models used in this study considered only climatic and topographic conditions, without accounting for other influencing factors such as soil properties, management practices, and biological interactions. Therefore, the results presented can provide a general estimate of the potential distribution of the species under the HadGEM-RCP 4.5 climate scenario, but for more accurate habitat management, further studies incorporating other environmental and biological factors are essential.
Samaneh Razavizadeh; Zahra Saedifar; Mohammad Khosroshahi; Fatemeh Dargahian; Sara Teimouri; Adel Jalili
Volume 32, Issue 2 , July 2025, Pages 201-220
Abstract
Background and ObjectiveThe environment harbors both valuable resources and potential hazards. Among these hazards, natural disasters—especially floods—pose a significant risk to society. Floods are recurring natural events that consistently lead to widespread destruction and considerable ...
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Background and ObjectiveThe environment harbors both valuable resources and potential hazards. Among these hazards, natural disasters—especially floods—pose a significant risk to society. Floods are recurring natural events that consistently lead to widespread destruction and considerable human and economic losses. Understanding the factors that influence river flood variability, particularly those related to water control infrastructure and drought occurrences, is therefore essential. This study aims to explore the effects of drought and dam construction on the fluctuations in the maximum flood levels of the Karun River.MethodologyTo investigate flood trends, data on instantaneous maximum discharge from the Ahvaz hydrometric station were analyzed over 50 years (1966–2016). Statistical methods, including analysis of variance, ranking of maximum discharges, and flood frequency analysis, were employed to assess the data. In addition, the study examined the status of dams within the Karun watershed and applied the SPEI drought index to explore the relationship between climate change and human interventions in shaping the river's flood regime.ResultsAn assessment of dam construction trends within the Karun watershed indicates that the expansion of dam infrastructure significantly contributed to the reduction of peak discharges. The findings show that dam construction played a major role in decreasing downstream peak flood discharges, particularly during the last two decades (1996–2016). However, in some cases, improper reservoir management has worsened the intensity of flash floods. After the construction of key dams such as Karun 1, 3, and 4, there was a noticeable decrease in peak discharges at the Ahvaz hydrometric station. This reduction underscores the importance of water control structures in flood management and outflow regulation. Nevertheless, in certain instances, altered flow patterns and delayed reservoir emptying have escalated the risk of flash floods, especially when sedimentation reduced reservoir capacity. The SPEI drought index analysis further reveals that extended drought periods have increased the likelihood of flash floods by lowering soil permeability and intensifying surface runoff. For example, in the final decade of the study (2006–2016), 53% of the basin experienced severe drought, 13% faced very severe drought, and 29% endured moderate to weak drought conditions. A small portion of the basin—about 1%—experienced wet conditions, and less than 5% recorded normal conditions. In contrast, during the first decade of the study (1967–1976), 18% of the basin was affected by drought, 22% experienced normal conditions, and 60% of the area was classified as wet.ConclusionThe impact of drought in the final decade has been associated with an increase in flood frequency. The majority of floods during this period were of low intensity, with short return periods (2 to 5 years). In contrast, earlier decades, characterized by less severe droughts, displayed lower flood frequencies but included events with longer return periods. These findings highlight the need to concurrently address both climatic and structural factors to improve water resource management and mitigate flood-related damages.