Leila Bakhshandehmehr; Mohammadreza Yazdani; Reza Jafari; Saeid Soltani
Volume 27, Issue 3 , October 2020, , Pages 463-484
Abstract
Research on the environmental controllers in plant communities is one of the research fields for many ecologists. Identifying the factors affecting the vegetation cover in the arid regions is the first step to recognize the destructive factors, which inhibit the growth and development of vegetation. ...
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Research on the environmental controllers in plant communities is one of the research fields for many ecologists. Identifying the factors affecting the vegetation cover in the arid regions is the first step to recognize the destructive factors, which inhibit the growth and development of vegetation. In the current study, using the structural equation modeling method and Partial Least Square – Structural Equation Modeling (PLS-SEM), climatic and pedological variables that affecting the vegetation cover in steppe rangelands of Zayandehrood basin of Isfahan province were identified and modeled. According to the results, soil clay content, maximum runoff height on the soil, temperature, and dryness of the environment are the most important variables affecting the quantity and quality of vegetation in the rangelands of the Zayandehrud basin. Besides, the role of climatic factors is more than soil factors in the distribution of vegetation in the region. The model presented in this research has good accuracy and high flexibility for modeling ecological phenomena.
Fateme Hadian; reza jafari; hosein bashari
Volume 22, Issue 4 , March 2015, , Pages 730-744
Abstract
Urbanization has been a major factor of natural resource degradation in the Semirom region of Isfahan province. This study aimed to evaluate the impact of urban development through land cover/ land use changes over a 37-year period using Landsat 1976 MSS and 2013 TM images and population data. First, ...
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Urbanization has been a major factor of natural resource degradation in the Semirom region of Isfahan province. This study aimed to evaluate the impact of urban development through land cover/ land use changes over a 37-year period using Landsat 1976 MSS and 2013 TM images and population data. First, necessary processing (geometric, radiometric, and topographic) was applied on images. Then, by using field assessment and GoogleEarth software, sample points were selected. The land use/ cover maps of the region and their changes were extracted by maximum likelihood classifier and post classification methods and their accuracy were assessed through overall accuracy and Kappa statistics. The accuracy assessment showed that the accuracy of maps in 1976 and 2013 was about (overall accuracy) 80% and 92%, respectively. The population was increased during three decades from 41973 to 65047 persons, which has led to an increase of 0.90 and 0.26 in the urban, and agriculture area and a 3 percent decrease of rangeland area. The 2.5 fold increase in bare land area in 2013 in comparison with 1976 indicated the severity of land degradation in the study area. Overall, drought and urban area attractions have facilitated the migration of people from villages to the city and had considerable negative effects in natural resources. Therefore, the region requires a holistic approach in all economic, social, and environmental developments.
Fatemeh Hadian; Hossein Bashari; Reza Jafari; Saeed Soltani
Volume 21, Issue 1 , June 2014, , Pages 176-187
Abstract
Selecting the appropriate satellite images is highly important to achieve acceptable precision and accuracy in rangeland assessment programs. This study aimed to evaluate Landsat5 (TM sensor) and IRS-P6 (AWiFS sensor) satellite images in three rangeland vegetation types in Semirom region, Isfahan. Ten ...
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Selecting the appropriate satellite images is highly important to achieve acceptable precision and accuracy in rangeland assessment programs. This study aimed to evaluate Landsat5 (TM sensor) and IRS-P6 (AWiFS sensor) satellite images in three rangeland vegetation types in Semirom region, Isfahan. Ten vegetation indices of different groups including slope-based, distance-based and plant-water sensitive indices were calculated and evaluated for all vegetation types. The percentage of canopy cover, litter, rock, gravel, stone and bare ground were determined using step-point method in radial direction (6000 points per rangeland type). Then, the correlations between the measured field components and spectral indices were compared. According to the results, vegetation indices extracted from TM sensor data had higher correlation with field vegetation cover due to its high spatial resolution. Factors such as characteristics of study area, range condition and vegetation types had also vital role in these correlations. The indices were tested against vegetation cover percentage in all vegetation types including Bromus tomentellus, Astragalus spp-Daphne mucronata- and Astragalus spp-Scariola orientalis. The highest determination coefficient was found between live vegetation cover and SSI index (r2=0.85) in Astragalus spp-Daphne mucronata vegetation type. Overall, the results showed that there was an inverse relationship between vegetation cover indices and rangeland condition. TM vegetation indices had minimum of 24 percent of determination coefficient in very poor range condition in comparison with other studied rangeland conditions. Therefore, the performance of a vegetation index highly depends on rangeland condition, vegetation types and also spatial resolution of remote sensing data.