Neamat Karimi
Volume 28, Issue 4 , November 2021, , Pages 652-671
Abstract
The main objective of the present study is to delineate all-natural resources of Iran with the priority of desert and semi-desert areas using indicators and criteria extracted from remote sensing data and new satellite image classification techniques. Accordingly, desert, semi-desert, and salinity areas ...
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The main objective of the present study is to delineate all-natural resources of Iran with the priority of desert and semi-desert areas using indicators and criteria extracted from remote sensing data and new satellite image classification techniques. Accordingly, desert, semi-desert, and salinity areas of Iran in conjunction with other natural resources areas (such as forests, rangelands, water bodies, and farmlands) were studied using time-series MODIS satellite images and different indices and parameters such as Albedo, NDVI, and surface temperature during day and night along with the temperature difference between day and night. Here, unlike the classical classification methods, based on using one-single satellite image and features such as vegetation density or surface temperature, the behavior of different natural resources over time, extracted from satellite images, was analyzed. Accordingly, the temporal behavior of each of the mentioned natural resource areas during 2019 was studied and analyzed using the remote sensing criteria. The basic object classification method was used to classify the country using the mentioned indicators using the least distance technique based on fuzzy logic. Based on results, about 41.2%, 14.8%, and 3.9% of Iran (totally about 60% of Iran) are classified as desert, semi-desert, and salty areas, respectively. By considering the percentage of rocky mountainous areas (11.3%), about 71.2% of Iran has no biological conditions (unsuitable for agricultural activities). As expected, desert and semi-desert areas are concentrated in central, eastern, southeastern, and southern regions of Iran, and no signs of such areas are found in the northern, northwestern, and western of the country.
Neamat Karimi
Volume 28, Issue 2 , June 2021, , Pages 341-356
Abstract
One of the most important features of the desert areas of Iran is the existence of windy sand dunes, which their dynamics and movement over time have distinguished them from many other geomorphological phenomena. The main objective of the present study is to evaluate the displacement of sand dunes in ...
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One of the most important features of the desert areas of Iran is the existence of windy sand dunes, which their dynamics and movement over time have distinguished them from many other geomorphological phenomena. The main objective of the present study is to evaluate the displacement of sand dunes in one of the largest sand complexes in the world, Rig Yalan in the east of the Loot desert. For this purpose, Sentinel-1 satellite images, which are considered SAR satellites, were used. In this regard, four Sentinel-1 satellite images were used at the beginning of summer 2017, 2018, 2019, and 2020. The offset tracking method was used to estimate the displacement of sand dunes in the study area. In the Offset Tracking method, the amount of horizontal displacements is measured by calculating the amount of deviation or correlation between two radar images taken from the same area. In this approach, the best match between the two images is achieved by maximizing the normalized cross-correlation. Based on the obtained results, during the study period, the amount of displacement of Yalan sand dunes in the closed and non-mobile areas has been up to a maximum of 3 meters per year in the large sand pyramids of the region, which are mainly concentrated in the center, west and south of the area. The movement of huts, ripple marks, longitudinal and transverse hills, and finally interconnected funnel-shaped sand pyramids of Yalan sand has not occurred in a fixed and definite direction and each part of it according to the morphological condition, the orientation of ridges as well as hill size and height different biases and displacements are observed. Based on the obtained results, all the features of the sand in Yalan sand are displaced on average about 0.94 meters per year.
behnoosh karimi mofarah; mansureh ghavam; abdolnabi Abdeh Kolahchi
Volume 28, Issue 1 , April 2021, , Pages 151-163
Abstract
Monitoring the changes in the rangelands makes it possible to make informed decisions about the application of management and protection plans. The purpose of this research is to monitor the changes from rangelands in the five-year period from 2000 to 2015 using geographic information systems ...
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Monitoring the changes in the rangelands makes it possible to make informed decisions about the application of management and protection plans. The purpose of this research is to monitor the changes from rangelands in the five-year period from 2000 to 2015 using geographic information systems and ENVI software. In this regard, Landsat images were first prepared at the specified times. By using the Minimum Distance, Mahalanobis, Maximum Likelihood, and Decision Tree, three NDVI, EVI, and SAVI indicators were modeled in 2016. Then, the best classification method was obtained by evaluating accuracy by Kappa coefficient and overall accuracy. As a result, other images for the past years were classified by this method and five classes were classified as low-density, semi-collimated, dense, non-covered, and gardens, and agricultural lands according to the subject. Educational points were also selected for both land surveying and ROI. The results showed that the tree of decision-making with the SAVI index yielded the highest accuracy with a precision of 94.73. Thus, although the area of low density and semi-dense pastures in 2005 and dense pastures in 2010 has increased, overall, during the period 2000 to 2015, all three classes of rangelands decreased. The attention and the class of gardens and agricultural lands have increased at a low level. Based on the findings of the study period, the behavior of the indicators is similar. From 2000 to 2010, the indicators were incremental, but in 2015, they decreased. Hence, it can be said
Maryam Mirdailamy; Mohammad Rahimi; Shima Nikoo; Ali Akbar Damavandi
Volume 27, Issue 1 , April 2020, , Pages 58-74
Abstract
In the past four decades, land use changes in Iran, have become more frequent as a human desertification factor, which has led to an intensification of land degradation in all types of land uses. In this research, due to the wide range of these changes, we used remote sensing technology to assess land ...
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In the past four decades, land use changes in Iran, have become more frequent as a human desertification factor, which has led to an intensification of land degradation in all types of land uses. In this research, due to the wide range of these changes, we used remote sensing technology to assess land use and vegetation changes in Damghan plain. The area of the study region was classified into three classes including unutilized land, lands with vegetation cover (agriculture and pasture) and urban areas using supervised classification strategy and the changes of the land uses were compared over four periods. The results indicated an increase of 184% and 1.07% respectively in urban land use and unutilized land use and a 15.7% reduction in lands with vegetation (agriculture and pasture). Using the Normalized Difference Vegetation Index(NDVI), the results of classification of vegetation in the region were such that class 1 (index less than zero), from 93.3 to 99.5 percent increase, class II( Between 0 and 0.2), from 5.6 to 0.38 percent, and the third class (index ranging from 0.2 to 0.5), from 1.1 to 0.01 percent, and class four (index ranging from 0.5 to 1) has changed from 0.03 to 0%, which indicates the validity of the findings from the review of the changes in land use, both of which indicate an increase in dry land and a decrease in vegetation. Also by using the Iranian model's climatic indices, the potential of desertification, the results of the 17-year calculations during the period of 1997 to 2013 indicated that desertification had decreasing trend in three classes: weak, severe and very severe, and increasing trend in the middle class. Finally, by combining the findings from the Iranian model and the results of remote sensing method, a weak trend in desertification based on climate criteria in the region was confirmed.
Mojtaba Pakparvar; Morteza Abtahi
Volume 8, Issue 4 , September 2019, , Pages 93-122
Mohammad Sadegh Kahkhakohan; Abolfazl Rajbar Fordoie; Seyed Hojat Mousavi; Abbasali vali
Volume 26, Issue 3 , September 2019, , Pages 754-771
Abstract
Drought and its effects is one of the world's major concerns. As one of the countries in the dry belt of the earth, Iran has always been and is facing environmental issues and natural hazards caused by drought. Therefore, this study aimed to monitor the aridity in Sistan and Baluchestan using remote ...
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Drought and its effects is one of the world's major concerns. As one of the countries in the dry belt of the earth, Iran has always been and is facing environmental issues and natural hazards caused by drought. Therefore, this study aimed to monitor the aridity in Sistan and Baluchestan using remote sensing data and geographic information system techniques for over a period of 15 years (2015-2000). In this regard, the MODIS satellite images from 2000 to 2015 were analyzed by applying the yearly Precipitation Condition Index (PCI) and Standardized Precipitation Index (SPI). Then, the drought changes were evaluated using supervised classification method and difference images. The results showed that the years 2007 and 2001 with an area of 157383.06 and 306.05 km2 had the highest and lowest levels of precipitation, and also with an area of 49511.1 and 69233.83 km2 had the minimum and maximum level of drought, respectively. The most severity change of drought has been in time for the 2002-2001 period and the place also belong to parts of Khash, Iranshahr and Sarbaz who takes 194302.93 km2 of the province. Finally, the general trend of changes in precipitation and drought is decreasing and increasing, respectively, requiring the major planning of resources conservation and risk and crisis management to rehabilitate and maintain the ecosystem of arid regions.
Mohammad Fayaz
Volume 12, Issue 1 , August 2019, , Pages 41-62
Ammar Rafiee Emam; Gholamreza Zehtabian; Amir Houshang Ehsani
Volume 11, Issue 3 , August 2019, , Pages 323-342
rasoul mahdavi; azam ali eivazi dokhtak; hamid gholami; Alireza kamali
Volume 24, Issue 3 , October 2017, , Pages 610-622
Abolghasem Dadrasi Sabzevar; Alimohammad Akhondali; Fereydon Radmanesh; Aliakbar Norouzi
Volume 24, Issue 2 , July 2017, , Pages 370-382
Abstract
The purpose of this paper was to make the preparation of soil surface moisture map applied in arid and semi-arid regions using satellite imagery of OLI and TIRS along with the calculated values for spectral reflectance, principal component analysis and Tasseled Cap transformation.Twenty-four predictor ...
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The purpose of this paper was to make the preparation of soil surface moisture map applied in arid and semi-arid regions using satellite imagery of OLI and TIRS along with the calculated values for spectral reflectance, principal component analysis and Tasseled Cap transformation.Twenty-four predictor variables were used and the most correlated ones were identified at three moisture levels of 4 to 5 percent, more than 5 percent and less than 4 percent by exploratory regression and bivariate correlation method through calculating the inflation factor of variance, Pearson coefficient and coefficient of explanation. The Moran'sI index was used for geo-spatial autocorrelation. Forty-seven soil samples were collected randomly by creating 1800-meter networks in a systematic algorithm and the soil moisture was calculated by W-thermal method. The estimation functions of soil surface moisture were derived in the form of partial least square regression (PLSR), enter regression and stepwise regression. All models had acceptable calibration. Our results clearly showed that the Landsat 8 data could be useful in estimating soil surface moisture and the accuracy of the functions extracted with stepwise regression method was more than that of other methods (RMSE=0.585 to 1.425 %). The models introduced for a moisture level of ≤5%, tend to over estimate (MBE= 0.788) and for other moisture levels tend to underestimate.
ardavan ghorbani; ardashir pournemati; mohsen panahande
Volume 24, Issue 1 , May 2017, , Pages 165-180
Abstract
The aim of this study was to estimate and map the plant group and total aboveground phytomass using Landsat 8 images in the rangelands of Sabalan Mountain. Images were selected on the 19th of July 2013 and field data were collected in April and July based on maximum matching with the phenology of the ...
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The aim of this study was to estimate and map the plant group and total aboveground phytomass using Landsat 8 images in the rangelands of Sabalan Mountain. Images were selected on the 19th of July 2013 and field data were collected in April and July based on maximum matching with the phenology of the study area and in the closest date to the time of image acquisition. Twenty-four sampling sites on six vegetation types were determined. In each site, 9 sampling plots, based on previous studies, which are required for minimum sample number according to the variance of vegetation distribution, were determined in a systematic-random method, and the aboveground phytomass of vegetation groups, such as grasses, forbs, shrubs and total, were determined using the harvesting method. Initially, to calculate vegetation indices, the averages of 16 pixel values of the location of sample units from the corrected images were derived and transferred to the software environment. The correlation matrices between the derived pixel values and field collected data for the 24 selected vegetation indices were calculated and used for the estimation of grasses, forbs, shrubs and total aboveground phytomass. The results showed that indices such as RVI, TNDVI and GNDVI had the highest correlation with the aboveground phytomass of grasses, PD312, IO and PD311 with the aboveground phytomass of forbs, RDVI, DVI and RVI with the shrubs, and PD311, PD321 and PD312 with the total aboveground phytomass (P <0.01). In the second stage, three of the indices, having the highest correlation with the aboveground phytomass of each group and entire previous stage, were selected, and Landsat8 images were used to calculate the aboveground phytomass of each vegetation group and the total aboveground phytomass was calculated. The aboveground phytomass maps of each group and the total aboveground phytomass were controlled with sampling points to assess the accuracy. The results of this study showed that the best maps were obtained using the TNDVI index for grasses aboveground phytomass, PD312 for forbs, RVI for shrubs groups and PD311 for the total aboveground phytomass. Moreover, some indices, such as PD311 and RVI, could be used for all growth forms and estimation of total aboveground phytomass (P<0.01) and (P<0.01). In general, Landsat 8 data could be used to estimate and map the aboveground phytomass of vegetation groups and to determine the carrying capacity of the total aboveground phytomass in Sabalan rangelands, having advantages based on cost, time and the ability to monitor large areas with repeatability potential in comparison with the ground-based methods.
Sina Sarabi; Ali Heshmatpour; Choghi Bayram Komaki; Abolfazl Tahmasebi
Volume 22, Issue 2 , August 2015, , Pages 392-405
Abstract
Analysis of drought and factors affecting it using remote sensing data has a high potential to improve scientific knowledge about the properties of drought and the effects of this phenomenon on vegetation. The present study was aimed to investigate the relationship between satellite indices and the SPI ...
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Analysis of drought and factors affecting it using remote sensing data has a high potential to improve scientific knowledge about the properties of drought and the effects of this phenomenon on vegetation. The present study was aimed to investigate the relationship between satellite indices and the SPI index in northern rangeland of Golestan province. For this purpose, SPI index in one, three, and six month- moving averages was calculated and then zoning maps were prepared using kriging. Then, using MODIS images and the corrections, required for this type of sensor, made on the images, a vegetation map was prepared using the indices of NDVI, SAVI and VCI. In order to synchronize the climate data with satellite images, a 9 -year-old common time base was selected . Finally, in order to investigate the relationship between vegetation indices with the SPI indices correlation coefficient and linear regression were used. The results indicated a good correlation between satellite indices and SPI indices in the peak months of vegetation growth. In addition, correlation between vegetation cover indices and three and six-month moving average in non-growing season, and with a one-month moving average of SPI in growing season was higher.
Zahra Abolalizadeh; Ataollah Ebrahimi
Volume 22, Issue 1 , June 2015, , Pages 21-30
Abstract
Sabzkouh protected area is located in central Zagros. This area, with a variety of natural ecosystems and landscapes, is very rich from the point of diversity of climate, topography, habitats and wildlife. Its ecosystems, like other semi-arid ecosystems of Iran, have undergone changes in their structure ...
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Sabzkouh protected area is located in central Zagros. This area, with a variety of natural ecosystems and landscapes, is very rich from the point of diversity of climate, topography, habitats and wildlife. Its ecosystems, like other semi-arid ecosystems of Iran, have undergone changes in their structure in recent years. Nowadays, Markov chain models are widely used in ecological studies to predict these changes quantitatively. For this purpose, satellite images and geographic information system were used to predict the future condition of the region using CA-Markov model. Finally, the land cover map of the region for the next fifteen years (2003-2018) was predicted by CA-Markov model. According to the prediction map, an increase in the area of agricultural lands, shrub/brush rangelands and forests of the region was observed, while the area of forbs rangelands and bare lands decreased. The results of these predictions provide a valuable tool to the managers and policy makers of natural resources and environment
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.
Akbar Fakhireh; Ahmad Pahlevanravi; Mahmoud Najafi zilaee; Mohsen Moradzadeh; Soheila Nouri
Volume 19, Issue 3 , December 2012, , Pages 457-468
Abstract
Detailed studies of vegetation in desert areas are almost difficult due to the limitations and conditions of these areas. Remote sensing technology with numerous capabilities can be used as an efficient method in these areas. This study was aimed to determine an appropriate vegetation index to assess ...
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Detailed studies of vegetation in desert areas are almost difficult due to the limitations and conditions of these areas. Remote sensing technology with numerous capabilities can be used as an efficient method in these areas. This study was aimed to determine an appropriate vegetation index to assess vegetation changes in the desert area of West Karkheh over a period of 18 years using satellite images of TM (1991) and ASTER (2008). After measuring the canopy cover, geometric and atmospheric corrections, different methods of detection and classification were applied on the images with maximum likelihood method. Results showed that PVI2 index was the best indicator to produce vegetation changes map during the study. So based on this index, final map of desertification was produced in the three classes with no changes and rehabilitation. The results showed that canopy cover increased up to 17.5% of the total area during the study period due to the implementation of desertification projects in some parts of the region and combined cultivation. These changes were classified in two classes of rehabilitation (69.8%) and desertification (30.2%).
Ali akbar Shamsi pur; Kazem Alavi panah; Hossein Mohammadi
Volume 17, Issue 3 , October 2010, , Pages 445-465
Abstract
The purpose of this study is to track and analyze the environmental effects of droughts by remote sensing indices in Kashan desert and dry zone. Temporal changes of droughts was evaluated using normal Z index in annual and seaonal (spring) scales. Spectral and thermal data from data series of NOAA-AVHRR ...
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The purpose of this study is to track and analyze the environmental effects of droughts by remote sensing indices in Kashan desert and dry zone. Temporal changes of droughts was evaluated using normal Z index in annual and seaonal (spring) scales. Spectral and thermal data from data series of NOAA-AVHRR satellite between 1998 and 2004 were used to determine the drought indices. Vegetative and thermal drought indices were calculated using NDVI, VCI and TCI values derived from NOAA-AVHRR data. Results from applying mentioned indices showed that this area had low vegetation index values as NDVI index was generally less than 0.2. According to NDVI and VCI maps, years of 2000 and 2001 were characterized as drought condition contrary to 2002 and 2004 as rainy years.However, land surface temperature (LST), TCI and VHI indices showed different temperature conditions specifically in the months of April and May. Using validation of results derived from remote sensing indices, test of significance between them and climatic indices was calculated.According to the calculations, climatic condition of the study area was more compliant with the results of vegetation indices. Also thermal condition of the environment was more accurately indicated by thermal indices. According to the results, applying remote sensing data in environmental studies of arid and desert regions like Kashan is recommended.
Mohammad mahdi Fatahi
Volume 16, Issue 2 , December 2009, , Pages 234-253
Abstract
The major part of Qom province areas have involved arid and desert conditions. Immethodical expansion of human acts with no attention to environmental affairs, caused intensifying desertification phenomena. In this paper, trend of desertification was studied with emphasis on land use changes and ...
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The major part of Qom province areas have involved arid and desert conditions. Immethodical expansion of human acts with no attention to environmental affairs, caused intensifying desertification phenomena. In this paper, trend of desertification was studied with emphasis on land use changes and as well as water quality and quantity resources. For assessment land use changes, satellite data (TM, 1985 and ETM+, 2002 ) and for evaluation of water quality and quantity resources changes, the hydrometric and climatic data were used. Comparison between land use maps of TM and ETM+, by using visual interpretation method, showed that areas of agriculture lands, rangelands, forest lands, sand dunes and salt lakes, have been decreased in 6.5, 4.14, 70.4, 24.2 and 15.8 percent respectively, whereas, another classes such as saline lands, urban and rural lands have been increased 26.6, 12.78 and 35.6 percent respectively. The output water of 2 main rivers of Qom province (Qomroud and Qarehchay) before establishment of Panzdah-e- Khordad and Saveh dams were 261 million m3, whereas it decreased to 66 million m3 after obstacle foundation. Before construction of Panzdah-e- Khordad dams, The fall of underground water level was 0.5 meter per year in Qom plain, which increased in averages to 1.4 meter per year after establishment of the dam. In addition, balance sheet of underground water, reduced remarkable. Totally, it seems that the human activities and retouching environment by him (especially construction of 2 dams on Qom rivers) are two main factors which have changed (with decreasing plant covering, salinization of major areas et cetera) and reduction of quality and quantity of water resources which could lead to aggravation of desertification in Qom province.
Nabi Ahsani; Jafar Oladi; Farhang Ghasriani; Mohammad Darvish
Volume 14, Issue 4 , February 2008, , Pages 539-558
Abstract
Kusalan range is a northwest-southeast mountain near Sarvabad, west of Kurdistan. The habitat includes a complex set of ecological functions and unique mountainous values such as Quercus forests, dense ranges, as well as various springs inside and around the region. So far, there was no study on the ...
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Kusalan range is a northwest-southeast mountain near Sarvabad, west of Kurdistan. The habitat includes a complex set of ecological functions and unique mountainous values such as Quercus forests, dense ranges, as well as various springs inside and around the region. So far, there was no study on the bioenvironmental habitat potential. This persuaded us to conduct a research on the habitat and ecosocial potentials according to IUCN categories using data bases like other literatures, 10 m2 panchromatic SPOT5 2005 data , expert opinions and field studies. Analysis of ecosocial and ecological bioenvironmental sources was implemented through a geographic information system (R2V, Arc/Info, Idrisi and Arc View). After qualitative and quantitative evaluation of various sources, land units were observed from overlaying maps of land form, soil categories, vegetation type, wildlife habitats, land use and conventional territory. Illustrated map show that about 70 percent of the area has a great conservational potential thus, the zonation process on the basis of IUCN definitions executed. The studied area was a habitat for 224 species of flora and 195 species of fauna classified as 5 categories: 29% core zone, 41% buffer zone, 14%expanded recreation zone, 3% intensive recreation zone and 14% cultural historical zone of Hawraman city and Pir-Shaliar annual ceremony and 13.2% reclamation zone including scientific, training values, virgin features and unique landscapes. Thus, Kusalan habitat worth to be introduced a national park (II) as a member of quadruplet national protected area in Iran. According to the results, GIS and RS approaches (hybrid interpretation of high resolution SPOT5 images) certainly can support determining and preparing bioenvironmental map sources in impracticable areas for conservational studies on IUCN criteria basis.
Mahdi Ahmadian; Mojtabah Pakparvar; Davood Ashourloo
Volume 14, Issue 4 , February 2008, , Pages 559-578
Abstract
Remote sensing technology is useful tool for spatial and temporal monitoring of natural phenomenon. Secondary salinization is known as the main causes of soil degradation where inappropriately land management occurred in a region. Total saline and sodic soils in Hamedan province are estimated at 70,000 ...
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Remote sensing technology is useful tool for spatial and temporal monitoring of natural phenomenon. Secondary salinization is known as the main causes of soil degradation where inappropriately land management occurred in a region. Total saline and sodic soils in Hamedan province are estimated at 70,000 hectare that includes 9.5 percent of total cultivable lands in this province. This paper tries to show important aspects of applying remote sensing in classification of sodic soils in Qahavand plain. The objective of this study is to monitor the sodic soils by using satellite information landsat-5&7. Classification of satellite imagery for alkalinity was carried out by investigation various bands and indexes such as PCA57, PCA123, NDVI, GRI, BRI. The supervised classification and spectral response angular mapping method used to classify the images. The soil maps were prepared by geographic information system in 1:50,000 scale. The results showed that total sodic soils areas were extended during last 11 years by 9.8 percent. The change in low sodisity class (A1) was 23.1 percent; in medium sodisity class (A2) was 13.7 percent and in sever sodisity class (A3) was 0.3 percent. The area of bare soils was 3005 hectares which is estimated 8446 hectares now and increased by 181 percent. The most important reasons for extension of sodic soils in this region are lack of proper land use and water management and conversion of land uses.
Hamid reza Moradi; Mohammad reza Fazel puor; Hamid reza Sadeghi; Zeinalabedein Hoseini
Volume 15, Issue 1 , January 2008, , Pages 1-12
Abstract
More than one-third of land in the world is located in the areas with arid and semiarid climate and desertification has increased in these areas during recent decades. Around 80% of Iran is located in arid and semiarid areas. Sand dunes as an indicator of desert land cover an area about 32 million hectare. ...
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More than one-third of land in the world is located in the areas with arid and semiarid climate and desertification has increased in these areas during recent decades. Around 80% of Iran is located in arid and semiarid areas. Sand dunes as an indicator of desert land cover an area about 32 million hectare. Among which 12-mil hectare has not been stabilized yet. Advancing moving sand dunes has resulted in much damage to agricultural products and urban areas. In this survey satellite images and aerial photos are used to evaluate the role of land use changes on desertification in 1955, 1997 and 2002. To do so, IRS image of 2002 and available aerials photos of 1955 and 1997 are used. Following making the aerial photos mosaic processing was done using ILWIS software and needed data completed by field surveying and the land use map was produced for two years. To produce the land use map using digital processing methods 10 sample set (training points) were selected uniformly in the area. After preprocessing including geometric corrections, image enhancement and band composition, image classification was done by maximum likelihood method and the land use map was produced. In this phase, obtained land use map was corresponded to the ground truth map which was achieved by field surveying and recording coordinate of points with GPS pixel to pixel and accuracy obtained from numerical classification estimated to be 45.3%. Then due to obtained low accuracy, the visual method used to produce the land use map so the accuracy of 78.5% achieved. Finally, the area of each land use and the rate of changes were calculated. The results indicate a decrease of 2000 ha in the area of the desert land from 1955 to 1997 and of 160 ha from 1997 to 2002 and an increase in the area of the other land uses. Results show no desertification in the study area, even though land degradation can obviously be identified in the area, which is resulted from the changes of gardens, and agricultural land uses to industrial and urban areas.
Kazem Dashtekian; Mojtabah Pakparvar; Jalal Abdollahi
Volume 15, Issue 2 , January 2008, , Pages 139-157
Abstract
Managing and monitoring of salinity is one of the most important affair in agriculture, specially in arid and semi arid area. For this purpose we have to use new technology like remote sensing and GIS. Most of scientist use maximum likelihood algorithm for mapping soil salinity, but in this method field ...
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Managing and monitoring of salinity is one of the most important affair in agriculture, specially in arid and semi arid area. For this purpose we have to use new technology like remote sensing and GIS. Most of scientist use maximum likelihood algorithm for mapping soil salinity, but in this method field sampling is necessary. In this study several methods were used for producing soil salinity map. These methods are Brightness Index (BI), Normalized Difference Salinity Index (NDSI), Salinity Index (SI), Yazd Salinity Index (YSI), maximum likelihood and average of regression with some Bands. By analyzing and comparing methods with real soil salinity map, suitable method for this region were: 1. Average of regression with standardized band 1,2 and 3. 2. salinity index method.
Hosein Arzani; Hasan Kaboli; Hamid reza Mirdavoodi; Mahdi Farahpoor
Volume 15, Issue 3 , January 2008, , Pages 320-347
Abstract
Importance of permanent range assessment is advice, because of continuous change, ecological aspects and economy of rangelands. The wide area of rangelands and facilities limitation for regular monitoring cause the requirement of the remote sensing application. The objective of present study was investigation ...
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Importance of permanent range assessment is advice, because of continuous change, ecological aspects and economy of rangelands. The wide area of rangelands and facilities limitation for regular monitoring cause the requirement of the remote sensing application. The objective of present study was investigation on reliability of ETM+ data for vegetation estimation. The study was carried out in Markazi province for five years. Satellite data of same time of grand truth data was obtained for each year. Vegetation indices were calculated after radiometric and geometric correction of images. Canopy cover of annual species, herbaceous species, grasses, shrub and total cover in five sites during five years were measured. Measurements were carried out in 60 plots two square meters rectangular quadrates along four 400 meter parallel transects. Before processing of the information, 15 random selected quadrates were kept for test of equation. In other case all data of four years was applied to calculate equation between vegetation indices and ground data and data of fifth years was used for test of model. Considering small area of quadrates against 30*30 meter pixel and probability of error involved with coordinate measurement by GPS correlation between mean data of each transect and indices also was studied. The results obtained from equation were compared with actual cover data using student t-test. Most indices have significant correlation with cover data, however sometimes equation did not gave correct estimation of cover compared with actual data. This was happened for life form that did not make considerable percent of vegetation composition. Generally application of transect data and calculation of equation based on four years data to estimate of fifth years canopy cover was more suitable way of using satellites data. Certainly using satellite system with more bands and better resolution and doing soil background correlation in arid regions would give better results.
Jalal Abdolahi; Mohammad hasan Rahimian; Mohammad hosein Savaqebi
Volume 14, Issue 3 , January 2007, , Pages 289-301
Abstract
Today, various indices have been developed for monitoring of vegetation cover in different climatic condition, which cause variation in aspect and spectral reflectance. Therefore, an index can give different values in different conditions. In addition, sparse vegetation and soil background are the other ...
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Today, various indices have been developed for monitoring of vegetation cover in different climatic condition, which cause variation in aspect and spectral reflectance. Therefore, an index can give different values in different conditions. In addition, sparse vegetation and soil background are the other limitations. Hence, combination of some indices can provide sufficient real information in such areas. Contribution of each parameter can be obtained from a statistical method. However, there is no guarantee that the high correlation coefficients would get a good vegetation cover map. It depends on the originality of each predictor variable. The main objective of this study was to identify some probable limitations of Landsat ETM+ images for mapping of vegetation cover in arid and semi-arid zones, especially in drought conditions. In addition, it suggests a method for mapping of sparse vegetation cover in such areas. For this purpose, vegetation cover percentages were measured in two dry and rainy years (2000 and 2002) in the Nodoushan basin, Yazd, Iran. Afterwards, Landsat ETM+ images of two mentioned dates were acquired and different indices were derived. In addition, some environmental factor maps were generated and aligned with other variables (e.g. DEM, Slope and Aspect maps). These data were analyzed using a multiple linear regression method and built regression equations of the form: vegetation cover (%) =1X1+2X2+…+ for each year. Xi’s are independent variables (Satellite data bands, different indices and environmental factors) and’s are regression coefficients and is a constant. According to the equations, vegetation cover maps were generated using ILWIS software capabilities. Then, their accuracies were determined. Results show that the 2002 map (rainy year) is more reliable than the 2000 map (dry year). It was also found that if a drought was occurred in the arid zones, soil background would be dominant and therefore, vegetation indices would not be able to estimate vegetation cover confidently
Morteza Akbari; Hamid reza Karim zadeh; Reza Modares; Bahareh Chakoshi
Volume 14, Issue 2 , January 2007, , Pages 124-142
Abstract
Desertification is the ecologic and biologic reduction which may occur naturally or non naturally. Desertification process usually effects arid and semi arid region and reduce the land efficiency very rapidly. This study has been conducted to evaluate and classify desertification with the aim of geographic ...
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Desertification is the ecologic and biologic reduction which may occur naturally or non naturally. Desertification process usually effects arid and semi arid region and reduce the land efficiency very rapidly. This study has been conducted to evaluate and classify desertification with the aim of geographic information system and remote sensing techniques. In this study, TM data of 25 shahriver 1369(16 October 1990) and ETM+ data of 16 shahrivar 1380 (7 October 2001) were used. Geometric, radiometric and sun height angle correction were carried out on the images. Supervised and unsupervised classification were used for both two images and 9 land uses were classified and compare quantitatively due to geomorphology and desertification attributes. Each main and partial desertification factor was input to geographic information database and scaled to make the map of desertification severity based on recommended method for Iran and FAO map of desertification vulnerability. The result of desertification severity which shows desertification condition, velocity and potentiality, showed that natural desertification occurs in 35 % of area with different medium, high and very high desertification severity. Anthropogenic desertification includes 65 % of study area with high and very high condition. But in desertification vulnerability map, very high desertification vulnerability was determined in 20 % of area with simultaneous human and animal effect and high desertification vulnerability was determined on 80 % area with only animal effect. According to the map, for arid region of north of isfahan, it was identified that range land use change to agriculture, improve agricultural patterns, over grazing, incident economic condition and ground water over exploitation are the most important anthropogenic factor, and drought and soil and water salinity are the most important natural factors. Desertification trend is enhancing to north west of the study area which will make trouble for rangelands, residential and industrial areas.
Abolghasem Dadrasi Sabzavari; Mojtaba Pakparvar
Volume 14, Issue 1 , January 2007, , Pages 33-52
Abstract
Desertification is one of the most difficult issues which has been taken into consideration in the world. The main objective of this study is determination of lands affected by desertification using remote sensing and geographic information systems, in Sabzevar. To meet the objective, Satellite ...
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Desertification is one of the most difficult issues which has been taken into consideration in the world. The main objective of this study is determination of lands affected by desertification using remote sensing and geographic information systems, in Sabzevar. To meet the objective, Satellite imagery of Landsat TM- 29 April 1987 and 13 May 2001 were selected and used, after haze and geometric correction. Principal Components (PC) and False Color Composit (FCC) were calculated, finally FCC521: RGB was selected for background of classification because of the best correlation. The Satellite images were classified by the maximum likelihood algorithm on the basis of field data. A study was conducted to determine the iso line of change in groundwater salinity and depth, in the study area, by using subsurface water data ( quality and quantity). The results show that on non saline parts and in the area of gypsum, the changes are negligible. The area of land uses are more or less the same except in agriculture which the land has increased by 3632 ha and in urban area which developed 672 ha. Merging and processing the whole data shows that the agriculture lands increased from 1987 to 2001. More salinity and less depth of groundwater are the results of groundwater data analysis, specially in south east part of the region