Ahmad Gillvare; Gholamreza Zehtabian; Hassan Khosravi; Hossein Azarnivand; Salman Zare
Abstract
Due to the importance of vegetation cover in these areas, the aim of this study was to investigate the effect of drought, on vegetation of HablehRood watershed.Initially, NDVI index obtained from MODIS sensor was used to study vegetation cover and then SPI index based on rainfall data of two basins in ...
Read More
Due to the importance of vegetation cover in these areas, the aim of this study was to investigate the effect of drought, on vegetation of HablehRood watershed.Initially, NDVI index obtained from MODIS sensor was used to study vegetation cover and then SPI index based on rainfall data of two basins in two arid and semi-humid climates was used for drought assessment (2001-2018) using image processing methods. The results showed that during this 18-year period, 53% of the region had droughts on average. Also during the period 2001-2003, drought was more severe than other periods (2003-2018). In addition, the highest vegetation index occurred in 2005, indicating that vegetation was affected by rainfall fluctuations in the region. The correlation matrix between the three indices indicated that NDVI had the same correlation with SPI and annual rainfall. The results of this correlation in dry and semi-humid climates showed that the correlation was 0.38 and 0.25, respectively. These results indicate that this relationship is positive and robust in different climates of a region؟. On the other hand, drought class is mainly located in dry and semi-humid climates, with 55.55% and 50% in relatively normal drought class, respectively. Based on the above, it can be concluded that using remote sensing data can monitor the response of semi-humid and dry arid ecosystems to climate change. The study also showed that arid and semi-arid regions are highly susceptible to climate change and human anomalies. Therefore, the destruction of these lands will have many environmental and economic consequences.
Reza Omidipour; Ataollah Ebrahimi; Pejman Tahmasebi; Marzban Faramarzi
Abstract
Vegetation canopy cover (VCC) and Above-Ground Phytomass (AGP) are the most important indicators of rangeland ecosystem’s structure and function, therefore their accurate evaluation and monitoring is vital for ecosystem welfare. Vegetation indices, are essential tools for assessing and monitoring ...
Read More
Vegetation canopy cover (VCC) and Above-Ground Phytomass (AGP) are the most important indicators of rangeland ecosystem’s structure and function, therefore their accurate evaluation and monitoring is vital for ecosystem welfare. Vegetation indices, are essential tools for assessing and monitoring VCC and AGP which have not been addressed under different managerial conditions, so far. In the present study, the effect of long-term grazing and enclosure (26-year) on the relationship between the VCC and AGP with vegetation indices were evaluated in the Sabzkouh protected area of ChaharmahalVaBkhtiari province using Landsat-8 images. VCC and AGP were evaluated in both grazed and enclosed area by 10 plots of 30*30-m in each of which three quadrates of 2×2 square meters were applied (totally 60 quadrates) in the June, 2016. The results indicate significant differences between grazed and enclosed areas in terms of VCC (57% and 46 respectively) and AGP (with 1656 and 1011 kg per hectare, respectively). The soil adjusted vegetation indices show a more significant prediction of VCC in enclosed and grazed areas (TSAVI1=0.828 and PVI3=0.884, respectively). The PVI2 index showed appropriate results for estimating AGP in both enclosed (R2=0.726) and grazed (R2=0.698) areas. The improved performance of these indies is mainly due to the adjustment of soil effects. Our results suggest that grazing caused a significant effect on the relationship between VCC and AGP with vegetation indices due to feasible changes in vegetation structure or composition. Therefore, using different indices is necessary to study and monitor different rangelands under management strategies.
Sina NabiZadeh; Ataollah Ebrahimi; Masoumeh Aghababaei; Iraj Rahimi
Abstract
The land use of the watersheds is one of the most affected and highly vulnerable due to developmental process which effect on the other variables such as the hydrological function. The purpose of this research is to monitor land use changes in the past and to investigate predictability of its future ...
Read More
The land use of the watersheds is one of the most affected and highly vulnerable due to developmental process which effect on the other variables such as the hydrological function. The purpose of this research is to monitor land use changes in the past and to investigate predictability of its future using Land Change Modeler (LCM) in the watershed of Farsan County of Chaharmahal-va-Bakhtiari province. For this purpose, the Landsat-5 TM images of 1986 and 2009 as well as the Landsat-8 OLI images of 2017 were analyzed. Land covers including residential areas, agricultural land, dryland farming, rangelands, rocks, water bodies, bare-land and snow were classified for the three periods. The prediction of land cover of 2017 was done using the LCM model based on Artificial Neural Network and Markov chain analysis after assessing model’s accuracy based on Kappa index. The land cover of 2027 was also predicted using a change probability table extracted from occurred changes from 1986-2017. The results show that the rangeland decreased by 4379-ha in the years 1986 to 2017, but the agricultural land increased by 1922-ha. This study proved that the LCM could accurately forecast future changes (85% overall accuracy). An increase of 149-ha of residential area and 100-ha decrease of rangelands in the study area was predicted for 2027. Therefore, while emphasizing the conservation of rangelands, it is necessary to study and use this technique to predict changes, its causes, as well as the consequences of land use changes at the broader scales.
jamal mosaffaie; mohammad reza ekhtesasi; Amin Saleh pourjam
Abstract
Study of geological units is one of the basic studies in many different sciences such as natural resources. The use of geological maps produced by geological survey is now the basic of geological studies in detailed-operating and investigative studies of natural resources. On the other hand, during the ...
Read More
Study of geological units is one of the basic studies in many different sciences such as natural resources. The use of geological maps produced by geological survey is now the basic of geological studies in detailed-operating and investigative studies of natural resources. On the other hand, during the last years, remote sensing technology has been introduced as a new and efficient tool for geological studies that in addition to proper precision, it has other benefits such as accessibility to impassable or inaccessible mountainous regions. In this study, comparing the accuracy of existing geological and remote sensing maps of Vartavan catchment of Qazvin province has been the object of the study which was evaluated with the ground realities. So first, maps of geological survey were examined. Then, various image processing techniques including False Color Composite (FCC), Principal Component Analysis (PCA), Optimum Index Factor (OIF) and Band Ratio (BR) were used to enhance different lithological units and finally, RS lithology map of the catchment was prepared. Considering the variety of rocks and formations of the study area, the FCC and OIF techniques have respectively the most capabilities for differentiation of the rocks. Kappa coefficient of 0.39 between the two maps indicates low agreement between them. Checking the accuracy of maps based on the ground realities showed that photo-lithological map is more accurate (97.1%) compared to geological map (52.5%).
shahrebanoo rahmani; Ataollah Ebrahimi; alireza davoudian
Abstract
In this study, three methods were evaluated for vegetation mapping. For remote sensing method, in addition to IRS data of LISSIII, Ddigital Elevation Model (DEM) and Normalized Difference Vegetation Index (NDVI) were used for classification of 14 classes of land covers mostly vegetation types using a ...
Read More
In this study, three methods were evaluated for vegetation mapping. For remote sensing method, in addition to IRS data of LISSIII, Ddigital Elevation Model (DEM) and Normalized Difference Vegetation Index (NDVI) were used for classification of 14 classes of land covers mostly vegetation types using a maximum likelihood algorithm. After comparing of produced vegetation maps, overall accuracy and Kappa index were 82% and 79.43% respectively when only the IRS were used. Whereas, the overall accuracy and Kappa index were increased to 93% and 90.63% respectively, when ancillary data of DEM and NDVI were added. Slope, slope direction, elevation above sea level, annual precipitation, temperature, and sun radiation were selected as the main physiographic after a broad literature review. Then the relationship between of these six factors with vegetation types was evaluated. so a multivariate logistic regression was used to draw vegetation map of the study area based on the sixth independent variables. The result showed a predicted vegetation map of 47.08% accuracy.Finally, in the morphological method, relationship between three maps of lithology, undulating form of geomorphology and faces with vegetation/land cover were determined using a neural network synthetic approach and predict vegetation map was drawn as the output. The accuracy of resulted map was 39.1%. Comparison of accuracy of vegetation mapping by three methods of RS, physiographic and geomorphological methods revealed that RS method of vegetation/land cover mapping is significantly promising due to a meaningfully higher accuracy even without using ancillary data such as DEM and NDVI in this method.
kazem Nosrati; Mohsen Mohseni Saravi; Hasan Ahmadi; Hosein Aghighi
Abstract
Estimation of evapo-transpiration is necessary in cases such as irrigation planning, determining of evaporation of the water bodies, water balance assessment, estimation of runoff and watershed management and ecological and meteorological studies. Evapo-transpiration can be determined precisely using ...
Read More
Estimation of evapo-transpiration is necessary in cases such as irrigation planning, determining of evaporation of the water bodies, water balance assessment, estimation of runoff and watershed management and ecological and meteorological studies. Evapo-transpiration can be determined precisely using field measurements. However, these methods provide evapo-transpiration just for limited areas from spatial point of view. This limitation has motivated the development of using remote sensing data to evaluate evapo-transpiration over vast area. Surface Energy Balance Algorithm for Land (SEBAL) is a new model that has been used at different areas all over the world for estimating of evapotranspiration. Due to the fact that no written report in evapo-transpiration estimation using this algorithm in the country has been published yet, the objective of this study is to investigate the validation of revised SEBAL model in mountainous region. In this project, actual evapo-transpiration values were estimated using MODIS image data and revised SEBAL model for mountainous region in 22 different dates in 2006 in Taleghan Drainage Basin. The result showed that the correlation between estimated and measured values is significant (R2=0.88, p<0.001). Thus, MODIS image data and revised SEBAL model were able to estimate actual daily evapo-transpiration values in Taleghan Drainage Basin. Therefore this revised algorithm could recommend as suitable method for further studies in different area with variation topography.
Molouk Royan; Adel Sepehri; Abdolrasoul Salman Mahini
Abstract
Remote sensing and aerial photographs are used to produce medium to small scale images. However, for detailed information especially to estimate rangeland vegetation canopy cover there is a need to larger scale images. It is therefore necessary to study the technical applicability of different devices ...
Read More
Remote sensing and aerial photographs are used to produce medium to small scale images. However, for detailed information especially to estimate rangeland vegetation canopy cover there is a need to larger scale images. It is therefore necessary to study the technical applicability of different devices such as short range light airplanes, kites, gliders and balloons. In this research, we focused on suitable flight height for rangeland vegetation canopy cover estimation using large scale balloon images in Incheh Broon area where we conducted field tests in September 2010. The balloons ascended to heights of 5, 10, 25, 50 and 100 m and higher. Using the taken images, vegetation canopy covers were estimated and compared with those obtained from field measurements. Results show that there is no significant difference between field and image estimation of canopy cover for heights lower than 100 m. We therefore suggest using balloon images acquired from up to 100 m height for estimating rangeland vegetation canopy cover.
Fazel Amiri; Hassan Yeganeh
Abstract
فرآیند ارزیابی پوشش گیاهی به وسیلة تصاویر ماهوارهای نیازمند استفاده از شاخصهای گیاهی است. شاخص گیاهی بطور گستردهای برای ارزیابی و پایش تغییرهای بو شناختی (اکولوژیک) ...
Read More
فرآیند ارزیابی پوشش گیاهی به وسیلة تصاویر ماهوارهای نیازمند استفاده از شاخصهای گیاهی است. شاخص گیاهی بطور گستردهای برای ارزیابی و پایش تغییرهای بو شناختی (اکولوژیک) مانند پوشش گیاهی، بیوماس پوشش سطح خاک و شاخص سطح برگ استفاده میشود. اهداف این مطالعه شامل بررسی قابلیت دادههای ASTER به منظور برآورد پوشش گیاهی در حوزه آبخیز قره آقاچ و همچنین انتخاب شاخصهای گیاهی مناسب در تهیه نقشه پوشش گیاهی منطقه، میباشد. پیشپردازشهای مختلف شامل تصحیح هندسی با استفاده از تصاویر موجود مربوط اردیبهشت 1387 با RMSE حدود 5/0 پیکسل انجام شد و تصحیحات اتمسفری و توپوگرافی به ترتیب به کمک روش تفریق عارضه تاریک و مدل لامبرت انجام شد. از شاخصهای گیاهی و طبقهبندی نظارت شده برای تهیه نقشه پوشش گیاهی استفاده شد. عملیات برداشت زمینی در اردیبهشت ماه 1387 در سطحی معادل 25/8962 هکتار آغاز شد. تیپهای مختلف گیاهی به روش نمونهبرداری سیستماتیک- تصادفی، سطحی که اختلاف مهمی در ترکیب فلورستیک- فیزیونومیک نداشت، به عنوان تیپ گیاهی مستقل و یکنواخت در نظر گرفته شد. در کل منطقه حدود 60 نقطه تصادفی انتخاب و اندازهگیری پوشش گیاهی به روش برآورد انجام گرفت. اطلاعات رقومی و شاخصها به عنوان متغیر مستقل و اطلاعات زمینی به عنوان متغیر وابسته معرفی شدند. معادلات مختلف با استفاده از شاخصها بر روی تصاویر اعمال و سپس تصاویر به 5 کلاس پوشش طبقه بندی شد. در نهایت نقشه پوشش و نقاط نمونهبرداری برای بررسی صحت نتایج، کنترل گردید. نقشه پوشش منطقه با اعمال پردازشهای گوناگون بر روی تصویر تهیه گردید. با بهره گیری از سامانه اطلاعات جغرافیایی تمام لایههای اطلاعاتی با یکدیگر ترکیب و نقشه پوشش اراضی منطقه تهیه شد. نتایج این پژوهش نشان داد که، شاخص NDVI همبستگی بالایی با درصد پوشش گیاهی داشت (01/0P?). صحت کلی و ضریب کاپا برای نقشه پوشش با شاخص NDVI به ترتیب برابر 5/68 % و 4/72 % بدست آمد. نتایج این مطالعه نشان داد که پوشش گیاهی با درصد تاج پوشش 40-20 درصد، وسیعترین طبقه تراکمی پوشش این منطقه میباشد. نتایج این پژوهش همچنان نشان داد که تصاویر سنجنده ASTER و شاخصهای گیاهی ابزار قدرت مناسبی برای تهیه نقشه پوشش گیاهی میباشد. بنابراین، می توان از نقشه پوشش تهیه شده از دادههای ASTER برای برآورد پوشش و تولید و ارزیابی مراتع استفاده کرد.
M Ghorbani; A.A Mehrabi; M Servati; A.A Nazari Samani
Volume 63, Issue 1 , June 2010, , Pages 75-88
Abstract
Nowadays, population growth and on the other hand resources limitations astonish authorities. Population changes cause variation in economic activities and land use changes. As a whole, overusing, improper land use and human disturbances over natural resources make environmental imbalances worse. In ...
Read More
Nowadays, population growth and on the other hand resources limitations astonish authorities. Population changes cause variation in economic activities and land use changes. As a whole, overusing, improper land use and human disturbances over natural resources make environmental imbalances worse. In recent decades, we have seen land use changes in Taleghan basin. Land use changes were produced by many factors, e.g. in abandoned lands, some parts of the region have been converted to residential areas and constructions. Since one century before, because of vicinity to population centers like Tehran and upland condition, this region has been a suitable place for recreation of travelers. Also one of the most important factors has been changed in population which has occurred in Taleghan. So that the statistical information shows substantial decrease in villages population in Taleghan. Similar to the, other regions in Iran, landuse changes especially in rangelands, is an important subject in Taleghan too. This paper tries to illustrate the relationship between population and land use changes in the given region of study and to detect the land use changes in a 15-year period. For determining the landuse, we used geographic information system and statistical methods, remote sensing also landSat images for 1987 and 2001 together. Population size were gained and analyzed for computing the population growth rate. According to what we concluded, in abandoned lands in given region of study the growth rate was positive and in other word, it increased and for other land uses this rate was negative together with negative increasing in all villages, therefore the population decreased. The villages of this region according to their magnitude of reduction in population growth and abandoned lands are: Gateh deh, Narian, Noviz oliya, Dizan, Jovestan, garab, Orazan, Nesa Bala, Mehran, Khachireh, Drapy. Thus, great number of settlers during these years migrated and the population decreased and following this trend, great area of rangelands (37.88%) which has already converted to rain-fed lands, has emerged in the form of abandoned lands in this region. In Gateh deh village, the area of rangelands had the maximum reduction and on the contrary, abandoned lands had the maximum amount of growth. Finally, it could be inferred that, there is a logical relationship between population growth and the area of abandoned lands.
