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; Seyed Zeinolabedin Hoseini; Mansoureh Seyed Hoseini
Volume 21, Issue 4 , March 2015, , Pages 756-768
Abstract
Precipitation is one of the factors affecting vegetation. Nowadays, satellite images are broadly used for monitoring the effects of precipitation variations on the vegetation changes. The aim of this study was to investigate the relationship between vegetation dynamic and precipitation variations using ...
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Precipitation is one of the factors affecting vegetation. Nowadays, satellite images are broadly used for monitoring the effects of precipitation variations on the vegetation changes. The aim of this study was to investigate the relationship between vegetation dynamic and precipitation variations using NOAA AVHRR images during the period of 1982-2006. Precipitation maps were created using the inverse distance weighting interpolation (IDW) method and time intervals of precipitation data. The study area was a forestland beside Caspian Sea, four rangeland vegetation types with grasses and shrubs, farmland areas and urban areas, located in Ardabil and Guilan provinces. To monitor the relationship between the precipitation and vegetation changes, the linear regression (NDVI, Y & Rainfall, X) method was employed. Based on the results, depending on the precipitation time, plant species, and growth form, the effect of precipitation on vegetation was different so that no significant relationship was observed between vegetation and precipitation in forestlands, farmlands, and urban areas. The highest correlation coefficient between spring precipitation and vegetation was related to the rangelands. In grassland areas, the correlation coefficient was higher than that of shrublands, whereas the reaction of grasslands to precipitation in various parts was different.
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.