Ebrahim Farahani; Mohammad Khosroshahi; Majid Hosseni; Seyamak Loghmani
Volume 14, Issue 4 , February 2008, , Pages 490-499
Abstract
Vegitation cover is one of the important environmetal factors which can determine desert areas. In this article, we determine desert areas in Tehran province by GIS. In the study area, dominant plant types and some of main ecological properties of them were assigned. Finally, by available information ...
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Vegitation cover is one of the important environmetal factors which can determine desert areas. In this article, we determine desert areas in Tehran province by GIS. In the study area, dominant plant types and some of main ecological properties of them were assigned. Finally, by available information and public characteristics of every plant type, desert area was separated. In this area, we distinguish 43 plant groups that 7 types of them belong to desert areas. This area is 307647 hectares which is formed 16.43 % of Tehran province.
Golriz Hossienzadeh; Hamid Jalilvand; Reza Tamartash
Volume 14, Issue 4 , February 2008, , Pages 500-512
Abstract
Regarding to the importance and role of enclosure as an appropriate management in the natural resources, specially protection of vegetation cover and the soil of pastures, the effects of different grazing intensities on the vegetation cover changesand chemicalsoil properties in countryside pastures ...
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Regarding to the importance and role of enclosure as an appropriate management in the natural resources, specially protection of vegetation cover and the soil of pastures, the effects of different grazing intensities on the vegetation cover changesand chemicalsoil properties in countryside pastures of Esklim Rood district (placed in west of Savad kooh township) was studied. These pastures investigated to reveal the effects of prohibition on the vegetation cover changes and some soil chemical properties at three conditions of Reference, Key and Critical areas. The results show that delicious (Class I) in the reference region, average delicious (Class II) in the key region, and low delicious or non delicious plants (Class III) in the critical region, have the most vegetation cover percentage. So that, perennial and delicious grasses such as Festuca ovina L, Ermopoa persica T. Dactylis glomerata L. had the highest vegetation cover percentage in the reference region but by the increase of grazing, delicious species decreased gradually and average or non delicious plants increased. This study revealed that soil of the reference region which had the highest density and vegetation cover had more organic material, total nitrogen, phosphorus, potassium, and less acid in the surface horizon than that of grazing region. Also, results show that short- term enclosure affected on the protection of soil and vegetation cover due to high productivity.
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.
Kian Najafi Shabankareh; Mohammad Khosroshahi; Mohammad Gholampoor
Volume 15, Issue 1 , January 2008, , Pages 95-113
Abstract
Resistant species to salinity and aridity and temperature fluctuation are approximately introducer of desert. These species have particular morphology compatibling themselves to fragile and acute condition of desert area. Some species accumulate water in their tissues. Some other species decrease leaves ...
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Resistant species to salinity and aridity and temperature fluctuation are approximately introducer of desert. These species have particular morphology compatibling themselves to fragile and acute condition of desert area. Some species accumulate water in their tissues. Some other species decrease leaves area and develope their root systems to use groundwater resources and some have particular phytocynthesis systems. As a general desert species with different mechanism resist against acut climate condition and unsuitable soil properties of desert regions. Characteristics of desert species distribution area can be determined the geographical domain of desert area. In this study dominant plant types in certain grupes and some of main ecological properties were assigned and related map in GIS environment was prepared. Finally, according to public characteristics of dominant species of every plant type and accompany species, desert area was sperated. In study area 22 plant group, each consist of some plant types was recognized. The distribution area of plant groups of Zygophyllum atripolicoides, Gymnocarpos decander and Hammada salicornica is about 730132, 599941 and 53260 hectar respectively.
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