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.
Seyed Mehrdad Kazemi; Hamidreza karimzadeh; Hosein Bashari; Mostafa Tarkesh Esfahani
Volume 25, Issue 4 , February 2019, , Pages 789-804
Abstract
Considering the role and importance of grazing on vegetation structural changes, thisstudy aimed to assess the effects of various grazing intensities on vegetation parameters in semi-steppe rangelands of Alavigeh, Isfahan. Three rangeland locations with relatively homogeneous ecological conditions ...
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Considering the role and importance of grazing on vegetation structural changes, thisstudy aimed to assess the effects of various grazing intensities on vegetation parameters in semi-steppe rangelands of Alavigeh, Isfahan. Three rangeland locations with relatively homogeneous ecological conditions and various long-term grazing intensities (light, moderate and heavy) were selected. Four perpendicular transects with 100 meters length (two parallel transects and tow transects perpendicular to the general slope of the area) were established in each site and vegetation parameters including vegetation cover, density and palatability class of the species were recorded in 10 plots. The Margalef richness index and Shannon-Vainer diversity and evenness indices of the plots were calculated. A one way ANOVA was used to compare the vegetation parameters in sites with various long term grazing intensities. According to the results, the sites with low and moderate grazing intensities had higher plant density and vegetation cover compared with site grazed heavily and these vegetation indices varied significantly between the sites (P< 0.05). The species composition of the light and moderate grazing areas mainly included class II species with 72% and 54%, respectively. The heavily grazed site was dominated by the species with low grazing palatability (69%). The plant diversity, richness and evenness indices of the sites with low and moderate grazing intensities varied significantly (p < 0.05). The log normal was the best fitted parametric model among species abundance models for the low and moderate grazed sites, indicating a stable vegetation community. Log series were fitted to diversity data in the heavy grazed site, indicating an unstable vegetation community. RDA analysis revealed that there was a distinct grazing gradient and three vegetation zones could be clearly separated with various vegetation compositions. Although vegetation condition is appropriate in the sites with low grazing intensity, also the vegetation regeneration can benefit from moderate grazing intensity. Biological considerations are required in the management of rangeland ecosystems in arid and semi-arid ecosystems due to the fragile nature of these ecosystems.
Seyed Mehrdad Kazemi; Hamidreza Karimzadeh; Mostafa Tarkesh Esfahani; Hosein Bashari
Volume 25, Issue 3 , November 2018, , Pages 536-546
Abstract
Soil serves as an important rangeland ecosystem component and evaluating the effects of management practices on structure and function of range ecosystems can assist managers to select the best option in their reclamation plans. This study aimed to compare the effects of long-term ...
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Soil serves as an important rangeland ecosystem component and evaluating the effects of management practices on structure and function of range ecosystems can assist managers to select the best option in their reclamation plans. This study aimed to compare the effects of long-term exclosure (33 years) and rest-rotation grazing system on some soil physicochemical properties in semi-arid rangelands of Hamzavi research station, Hanna- Semirom in Isfahan province. Six transects were established in each area and three plots of 2m2 were placed along each transect randomly and 72 soil samples were collected from five points of the plot at the soil depth of 0-10 and 10-30 cm. Soil properties such as pH, EC, CaCO3, organic carbon, absorbable phosphor, total nitrogen, K, Ca, Mg, soil saturated percentage, cation exchange capacity, soil clay, silt, sand, and fine sand contents were measured in the soil laboratory. Independent t-test was used to compare soil properties in both areas. Results revealed that soil properties were more appropriate in areas under long-term rest-rotation grazing system compared with exclosure area. According to the results, most soil properties were differed significantly (α = 5%) due to rest-rotation grazing system in both areas, except pH, Mg, soil saturated percentage, silt, sand, and fine sand contents. This study showed that rest-rotational grazing systems can maintain ecosystem health condition in semi-arid area as well as decrease the costs of animal husbandry and is a more appropriate management option for ranchers compared with long-term grazing exclosure.