JWSS - Journal of Water and Soil Science

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Geologic and pedologic controls are the main factors determining the behavior of elements in natural soil environments. In order to assess the role of these factors on content and distribution of selected major and trace elements in soil, six parent materials including: phyllite, tonalite, periditite, dolerite, shale and limestone were selected in Fuman-Masule region. Soil genesis and development of representive residual pedons were studied for each parent material and the total content of Si, Al, Ca, Mg, Fe, Ti, Mn, Ni, Co, Cr, Cu, Pb, V and Zn were compared among them. Enrichment/depletion patters of trace elements were assessed using Ti as reference element. Generally, Cr, Ni, Co and V are highest in soils derived from peridotite (984, 285, 53 and 204 mg/kg, respectively) and dolerite (1023, 176, 39 and 185 mg/kg, respectively). In the same way, Si and Al exhibit the features of parent materials in the sense that the lowest content was observed in soils developed on peridotite, dolerite and limestone. Zinc and Pb are highest in soils derived from shale (106 and 27 mg/kg, respectively). In a given pedon, different elements exhibited different enrichment/depletion patterns moreover, a given element may behave differently not only in soils with different parent materials but also, in some cases, in soils developed on similar lithology. Lead, Zn, Cu and Mn have been generally enriched in most pedons, except in some acidic and strongly leached soils, whereas Co, Cr, Fe, Ni and V have been leached, especially from Dystrudepts and Eutrudepts. The latter elements, however, showed enrichment trend in Hapludalfs and Argiudolls parallel to the development of illuvial B horizons.

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Geologic and pedologic controls are the main factors determining the distribution of elements in natural soil environments. In order to assess the role of these factors in the content and distribution of major elements of soil, six parent materials including phyllite (Ph), tonalite (To), periditite (Pe), dolerite (Do), shale (Sh) and limestone (Li) were selected in Fuman-Masule region. Soil genesis and development of representive residual pedons were studied for each parent material. Total content of Si, Al, Ca, Mg, Fe, Mn, K, Na, Ti and P of soil horizons were measured and compared to the geochemical and mineralogical composition of parent materials. Maximum concentrations of Fe2O3 and MgO were found in the soils derived from Pe and Do however, these soils had low content of SiO2 and Al2O3, which is in conformity with the geochemical composition of the parent rocks. On the contrary, FeCBD content of these soils was lowest, indicating the low degree of soil development and, by the same fact, the importance of inheritance factor in soil Fe concentration. However, comparison of total Fe and FeCBD in Li1, Sh2 and To2 revealed that relative development of these pedons is higher than the others. Silicon depletion in Ph1, To2 and Sh2 pedons, relative to parent rocks, is higher than in Pe and Do pedons. However, this element is enriched in Li pedons. MnO content of Pe and Do pedons is governed by geogenic factors, while in Sh pedons, pedogenic factors, especially redox conditions, play the major role. Exchangeable forms of Ca and Na are determined by soil properties rather than by parent material type. Notwithstanding the redistribution of all major elements throughout pedons due to soil forming processes, the importance of inheritance factor in soil Si, Al, Mg, Fe, K, and Ti is higher than pedogenic factors.

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In order to study land degradation from the soil genesis and micromorphological perspective, ten soil profiles were dug and described on five slope positions in both forest and deforested cultivated land. The soil samples were taken from all horizons for physico-chemical analysis and micromorphological studies. Forest soils had a well developed argillic and calcic horizons and also mollic epipedon. These soils were classified as Alfisols and Mollisols. Carbonate leaching into the depth of soil profile and translocation of clays to lower layers and formation of developed soils are by no means related closely with the dense forest cover and its subsequent landscape stability and favorable leaching conditions. Dominant soil orders in this area were Inceptisols and Mollisols. In cultivated landuse, no argillic horizon was observed except in toeslope position. Absence of argillic horizon or its elimination following deforestation is one of the most important and obvious pedogenetic evidences of land degradation after land use change. Outcropping of high carbonatic layers (calcic horizon), disappearance of mollic and formation of ochric epipedon, presence of redoximorphic features attributed to runoff in lowland, decrease of solum thickness, and change of soil color were the other pedogenic indicators for land degradation in the study area. Microscopic observations showed that granular and crumb microstructures with high porosity were converted to massive and compact ones with low porosity in the deforested area. Disappearance of clay coatings besides absence of excremental pedofeatures were the other important micromorphological evidences of erosion and land degradation.