چكيده لاتين :
Introduction
Kalut is a wind-eroded ridge with a very streamlined shape developed in different lithologies in numerous deserts of the world. The features have been described as resembling an inverted ship’s hull. The windward face of the Kalut is typically blunt-ended, steep and commonly the highest part of the feature, whereas the leeward end declines in elevation and tapers to a point. Kaluts usually are formed parallel to one another, typically occurring as extensive fields. Kalut fields commonly occur as tight arrays, separated from one another by either U-shaped or flat bottomed troughs, or as widely spaced, highly streamlined features on wind-beveled plains.
Areas where Kaluts are present include Central Asia, the Lut Desert of Iran, northern Saudi Arabia, Bahrain, the Egypt, the central Sahara, the Namib Desert, and the Peruvian Desert. In the Lut Basin in southeastern Iran, Kaluts up to 80 m high form very elongate ridges with flat to rounded summits, separated by troughs > 100 m in width; variations in the competency of the eroding bedrock, possibly related to variations in depositional conditions, may govern the resulting final shape of individual Kaluts. Gypsiferous clay layer, with 10-15 cm thickness, blankets the Lut Kaluts, and inhibits further growth of the water carved gullies on the steep margins of the features.
The Kalut morphometric parameters are important in the definition of their morphological indexes. Also, relationships between them can be considered as modeling infrastructures of the form, natural and phenomenal indexes. Therefore, the purposes of this study are the assessment of relationships and models presentation of Kaluts morphometric parameters, and grouping of Lut Kaluts using statistical methods.
Materials and Methods
The study area is located in the western part of the Lut playa. Lut playa (Dasht-e Lut), with area about 54000 km2, is a low region in the southeastern of Iran consisting of several large basins. The Kalut field of Lut, with area 6481.6 km2, is located between 29° 30ʹ and 30° 49ʹ N, and 57° 47ʹ and 59° 53ʹ E.
At first, studied area is recognized by satellite images and Digital Elevation Model. Then, Kaluts and their morphometric parameters are sampled and measured using one-dimension method and linear sampling unit. So that, first, in the study area 3 transects was drawn upon DEM (pixel size 30 * 30 meters) in Global Mapper software. Totally, 108 Kaluts were sampled that 32, 47 and 29 numbers belong transects No. 1 (north), No. 2 (center) and No. 3 (south) respectively.
To evaluate Kaluts, their morphometric parameters measurement was did via drawing of profile coinciding to brink and cross-section coinciding to summit of Kaluts upon DEM. So that, length, windward slope, leeward slope parameters along of profile and right height, left height and width parameters along cross-section were measured.
Finally, a data matrix was prepared for modeling. The data sets were modeled using SPSS software and regression analysis, one-way variance analysis and Tukey post-hoc test techniques. For this achievement, at start, simple and multiple regression analysis were reexamined. Then, the most important and the most suitable of relationships were selected. One-way variance analysis and Tukey post-hoc test techniques were used to evaluate and group the study Kaluts, comparatively.
Findings and Results
The recognition of Kalut morphometric parameters is important in the definition of their morphological indexes, and relationships between them can be considered as modeling infrastructures of form, natural and phenomenal indexes. Therefore, in this study, we have assessed and presented the relationships and models among morphometric parameters and we have grouping Lut Kaluts using statistical methods.
The obtained results from simple regression show the significant linear relationship maximum of length and width with R. Square 0.415 and significant relationship of height with windward face for quadratic and cubic equations with R. Square 0.386 and 0.395 respectively.
The results of multiple regressions illustrate the significant relationship maximum of height with other parameters with R. Square 0.862 and the significant relation minimum of length with R. Square 0.423.
The obtained results from one-way variance analysis and Tukey post-hoc test represent that there is statistical significant difference between 3 transects from viewpoint of height in level ? ? 0.05. Also, the result of subgroups congruence shows that we can classify the study transects in several subgroups.
Conclusion
Systemic geomorphology investigates the function of geomorphic landscapes, and also, analyses the relationships between forms and processes. Efficiency of this approach is very important when there are linear and non-linear reciprocal relationships among elements of system. Aeolian deflation and abrasion are the most important factor in the formation of Kalut. The unidirectional prevailing wind, as a stimulus force, causes the input of wind energy and the output of material from Kalut system. Processes such as sediment characteristics prevent from aeolian deflation and abrasion as a barrier force. The consequence of these forces causes the formation of ridges and troughs as Kalut fields. In the study, relationships among morphometric parameters of Lut Kaluts are examined using regression analysis, one-way variance analysis and Tukey post-hoc test techniques. The results indicate that we can classify Lut Kaluts into four groups:
First group: relationships with average R. Square and Sig. in level ? ? 0.01.
Secondary group: relationships with average to weak R. Square and Sig. ? ? 0.01.
Third group: relationships with weak R. Square and Sig. ? ? 0.05.
Fourth group: relationships with very weak R. Square and non-significant.
Among multiple regression models, length parameter has non-significant relation with other parameters in the level ? ? 0.05. On the other hand, height justifies width, windward face and leeward slopes parameters, but length don’t justify other parameters except width. These relations are reciprocal, and parameters have such a situation than each other.
The results of one-way variance analysis show that there is significant difference between transects from viewpoint of height (Sig. = 0.007 and F= 2.64). However, real difference in height value is average among transects (Eta Square= 0.048). Tukey post-hoc test represents that average values of height is different in transect No.1 (M=44.21 and SD=4.203) with transect No.2 (M=38.25 and SD=2.201) and transect No.3 (M=34.18 and SD=1.96). Also, the result of subgroups congruence shows that we can classify the study transects in several subgroups.
According to relationships among parameters and aerodynamic form of Lut Kaluts, we can conclude that unidirectional prevailing wind and its canalization into corridors; as productive factor, and muddy coverage on ridges, material roughness and vegetation; as preventive factors, are caused the formation of Kaluts. The wind deviation by broad width of Kalut justifies the slope maximum and the highest point in initial part of windward face. Also, the elongation, narrow part, minimum elevation and slope in the leeward end of Kaluts are justified via the convergence, shear velocity reinforcement and predominance of wind upon ridge. From non-relations or weak relations of length with other parameters can be concluded that factors such as wind divergence at the first part of Kalut and its convergence in the end Kalut are the vindicator of the Kalut length.
