Showing 5 results for Topography
S. E. Sadati, S. F. Emadian, H. Jalilvand, J. Mokhtari, M. Tabari,
Volume 11, Issue 41 (10-2007)
Abstract
The present research was conducted to find the influence of some topographic factors on distribution of large-leaved lime (Tilia platyphyllos Scop.) and its natural regeneration characteristics in "Vaz" forest (northern Iran). After identification of site and preparation of topography map, selective sampling method was carried out for tree inventory in plots. The sample plots were circular in 1000-m2 areas with at least 2-3 dominant lime trees in each. In the plots, altitude, slope gradient, direction, forest storey, tree type and natural regeneration were investigated. Results indicate that in this habitat the average diameter at breast height and height of Tilia platyphyllos is 36.9 cm and 23 m, respectively. Tilia platyphyllos prefers 1200-1400 m altitude, 75-100% slope gradient and northeastern to eastern directions and benefits from denser trees in these environments. It consists of some tree types together with Fagus orientalis, Carpinus betulus and Parrotia persica, whereas the dominant type is Tilia platyphyllos-Fagus orientalis. In most of tree types, lime occurs in the upperstorey. Natural regeneration of lime is often observed as sprout (coppice shoot).
H. R. Owliaie,
Volume 16, Issue 62 (3-2013)
Abstract
Iron and manganese oxides as well as hydroxide minerals are among active constituents in soils because they are sensitive to environmental changes and often move frequently along soil profile. Therefore, their chemical forms content and their ratios are used as a soil developmental criterion. The present study was conducted in order to evaluate the effects of topography and drainage conditions on chemical forms of Fe and Mn along a soil catena in Dasht-e- Roum plain, in Kohgilouye Province. According to the results, maximum pedogenic Fe and Mn (Fed and Mnd) was found in more stable geomorphic surfaces. Higher values of Fed and Mnd were mostly observed in surface horizons compared to soil depth. Aquic soils exhibited higher contents of poorly crystalline Fe and Mn (Feo and Mno) and higher contents of Fed and Mnd. A significant correlation between clay content and Feo, Mno, Fet and Mnt contents was found. In addition, aquic condition increased Feo/Fed, Mno/Mnd and Mnd/Fed, 3.1, 4.3 and 1.9 times respectively but decreased the Fe crystallinity index 2.6 times. Aquic soils seem to have more favorable conditions for the formation of pedogenic Mn compared to pedogenic Fe, hence higher content of Mnd/Fed was observed in these soils
M. Zare, M. Soufi, M. Nejabat, L. Jokar,
Volume 18, Issue 67 (6-2014)
Abstract
Gully erosion and sedimentation have high priority in Fars Province due to the losses from destruction of lands, roads and civil structures. In the present study, in order to evaluate the threshold for the development and initiation of gully topography in Fars province, two regions were selected including Allamarvdasht, Lamerd and Fedagh, Larestan. 30 gullies were selected in each mentioned area. Morphometric parameters were measured and topography threshold was drawn. To evaluate the effect of measured parameters on topography threshold, each gully was clustered based on parameters and cluster analysis. To determine the effect of dominant hydrologycal processes on gully initiation and development, the multivariate analysis was employed using SPSS (version 14) software. Using the power relationship between watershed area and slope of each gully, the dominant hydrological processes in gully initiation and development were determined by means of Excel software and were compared with coefficients of foreign regional studies. The results showed that in the two studied regions, the most effective hydrologycal process was surface runoff. Results also demonstrated that in these regions changing the shape of upstream basin topography to circle and their expansion have increased the threshold of watershed topography of gully erosion. Increasing the sodium absorbtion ratio and removing the ground cover reduce the threshold of gully erosion topography. Increasing the depth of gullies and soil organic matters resulted in greater relative threshold of topography.
H. R. Owliaie, M. Najafi Ghiri,
Volume 18, Issue 70 (3-2015)
Abstract
Topography and land use are among the most important factors affecting the soil formation. Chemical forms of Fe and magnetic susceptibility (χ) are widely used for the evaluation of soil development. This study was conducted in order to determine the effect of these factors on χ. A toposequence was selected in Madvan Plain, Northern Yasouj. Nine soil profiles (paddy and dryland soils) were dug and sampled from diagnostic horizons. Magnetic susceptibility was measured by Bartington Dual Frequency, MS2 Meter at frequencies of 0.46 and 4.6 KHz. Results indicated that less amounts of χ, frequency dependence of χ (χfd%) and CBD extractable Fe (Fed) (3.1, 2.6 and 2.7 times, respectively), and more quantities of oxalate extractable Fe (Feo) and Feo/Fed ratio (5 and 7.2 times, respectively) were measured in paddy soils. The highest value of χ was observed in pedons located on plateau and piedmont plains, and the lowest belonged to those located on river terraces with aquic conditions. Compared to paddy soils, χ enhancement at soil surface was greater (17%) in dryland soils. A positive correlation existed between χ and some soil characteristics such as Fed, clay content and χfd%.
M. Zeraatpisheh, Sh. Ayoubi, H. Khademi, A. Jafari,
Volume 23, Issue 1 (6-2019)
Abstract
Landscapes are considered as a series of different land units with a size, shape and location arrangement that are permanently under the influence of natural events and human activities. Understanding the dynamics and heterogeneity of landscapes and environmental changes is of great importance. In order to quantitatively analyze and interpret the factors affecting the changes in the environment and terrain diversity, diversity indices were used to analyze the ecosystem. In this study, the relationships between soils evolution and geomorphic surfaces were investigated by applying pedodiversity indices in a part of a semi-arid region of Chaharmahal-Va-Bakhtiyari Province. In the studied area, three orders were recognized: Mollisols, Inceptisols, and Entisols. The results showed that soil evolution in the studied area was mostly influenced by topography, parent material and the underground water level; that is, in the higher lands, the lowest evolution was observed while in the plain ones, the soil of the higher evolution observed. In addition, the effect of geomorphic surfaces were obvious. Pedodiversity indices increased under the decrease of the hierarchy levels. In addition, the obtained equations revealed the nonlinear relationships in the area of geomorphic surfaces. The positive and nonlinear relationship between pedodiversity indices confirmed the nonlinear dynamic system in the studied soils.
