نویسندگان
1 دانشیار دانشکدهی جغرافیا، دانشگاه تهران
2 دانشجوی دکترای ژئومورفولوژی، دانشگاه تهران
3 دانشجوی کارشناسی ارشد ژئومورفولوژی، دانشگاه تهران
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
Comparative and Analysis of Nebkas Geomorphologic Features Four Plant Species in West of Lut (East of Shahdad - Takab Plain)
Maghsoudi M. ?
Assistant Prof., Faculty of Geography, University of Tehran
Negahban S.
Ph.D. Candidate in Geomorphology, Faculty of Geography, University of Tehran
Bagheri said-Shokeri S.
Ph.D. Candidate in Geomorphology, Faculty of Geography, University of Tehran
Chezgheh S.
MA. Student in Geomorphology, Faculty of Geography, University of Tehran
Extended Abstract
Introduction
Vegetation has a major role in dynamic and morphology of sand dunes in desert area. Vegetation affects the movement of sands and traps sands that are transported by wind. Nebka is one of the most important accumulations landforms in desert area. The type and species of vegetation can affect on the characteristic of Nebka. This research attempted to identify echogeomorphology characteristic of Tamarix and Prosopis cineraria nebkas in the west of Lut Plain in southeastern of Iran. Lut is a desert area with many especial landforms such as Yardang, Barkhan, Star dunes and other desert landforms covering 175000 sq. kilometers area.
Methodology
Descriptive and analytical methods were used for studying of Nebkas. In addition morphometric characteristic of selected nebkas were measured during the fieldwork. Moreover, the sediment samples were taken and components of landforms were measured. After identification of study area using aerial photos and satellite images, sediment samples were taken. In fact, we identified four transects and selected some Nebkas in transects, morphometric characteristic were measured. Also statistical parameters of samples using SPSS software were calculated. Finally, using shaker and granulometry method, grain size distributions were analyzed. For analyzing of grain size distribution, we used Gradistat 4.5 to calculate all statistical parameters of grain size taken from Nebkas sediments.
Results and Discussion
Among 30 selected Nebkas’, four types of plant with different morphometric characteristic can be recognized. Correlation analysis between nebkas morphometric characteristics, such as dunes height, plant height, dunes area, width and perimeter, showed that the correlation between above mentioned characteristics and Tamarixaphylla and Prosopis Cinerarias, in 99 percent of significance level are high. In addition, correlation between above mentioned characteristics with Tamarix Kotschyi and Tamarix Floridas in level of 95 and 99 percent of significance level are also high. Mean heights of Nebkas in Tamarixaphylla are 7.8 meters and mean height of plant crowns are 11.09 meters. Results for other kinds of Nebkas with different plants are lower. Moreover in point of view of area, perimeter and width’s mean, maximum results belongs to Tamarixaphylla with 322.39, 68.3 and 18.24 meter. Also results from granulometry show that coarser grain belongs to Tamarixaphylla and other kind located at next ranks.
Conclusion
The results from statistical analysis of morphometric characteristic of Nebkas provide reliable information. Increase in height of the plant crowns is accompanied with an increase of Nebkas height and the consequently increase of Nebkas area. In addition, increase of height causes perimeter and width of Nebkas to be increased. These conditions are identical for all Nebkas. Tamarix Aphylla nebkas with higher height in comparison with other kinds of Nebkas plant have bigger areas, perimeters and widths. In inverse situation, Tamarix Kotschyi has lower morphometric characteristics values such as height, area, width and perimeter relative to other kind of plant in study area. Moreover, results from mean of area, perimeter and width of Nebkas show that the higher values, belongs to Tamarix Aphylla with 322.39, 68.3 and 18.24 meters. Second rank belongs to Tamarix Florida and next ranks belong to Tamarixaphylla, Prosopis Cineraria and Tamarix Kotschyi. Maximum standard deviation, variance, kurtosis and skewness belong to Tamarixaphylla, Prosopis and Tamarix Kotschyi. Moreover, between all Nebkas, maximum area, perimeter and width belongs to Tamarixaphylla with 565.7, 93 and 30.5 meter and the minimum area and perimeter belong to Tamarix Florida with 11.84 and 11 meters. Finally, the minimum width belongs to Tamarix Kotschyi with 2.9 meter. Results from granulometric analysis of grain size distribution demonstrate that the coarser sands are belonging to sediments of Tamarix Aphylla, other kinds of plants located at lower rank. Wind data analysis shows that the slope of windward sides of nebkas are more than other parts. In fact, directions of dominant winds are from north and north west, and north and north west side of nebkas are stuper.
Keywords: Tamarix, Nebka, Ecogeomorphology, Shahdad, Lut
کلیدواژهها [English]
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