Effects of environmental factors on classification of loess-derived soils and clay minerals variations, northern Iran Effects of environmental factors on classification of loess-derived soils and clay minerals variations, northern Iran

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Vol15 No.5: 976-991

Title】Effects of environmental factors on classification of loess-derived soils and clay minerals variations, northern Iran

Author】Mohammad AJAMI1,2; Ahmad HEIDARI1*; Farhad KHORMALI2; Manouchehr GORJI1; Shamsollah AYOUBI3

Addresses】1 Department of Soil Science, College of Agriculture and Natural Resources, University of Tehran, Karaj 31587-77871, Iran; 2 Department of Soil Science, Faculty of Water and Soil Engineering, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan 49138-15739, Iran; 3 Department of Soil Science, College of Agriculture, Isfahan University of Technology, Isfahan 84156-83111, Iran

Corresponding author】Ahmad HEIDARI

Citation】Ajami M, Heidari A, Khormali F, et al. (2018) Effects of environmental factors on classification of loess-derived soils and clay minerals variations, northern Iran. Journal of Mountain Science 15(5). https://doi.org/10.1007/s11629-017-4796-y

DOI】https://doi.org/10.1007/s11629-017-4796-y

Abstract】Land-use type under different topographic conditions and human activities affects soil development. We investigated the effects of land-use, topography and human activity on soil classification changes in the Toshan watershed in northern Iran. Seven representative pedons derived from loess parent materials were studied on different land-uses and topographic positions. The studied pedons in forest (FO) on backslopes and footslope were classified as Calcic Haploxeralfs and Typic Haploxeralfs, respectively. The soils in abandoned lands (AB) and orchards (OR), where formerly under natural forests, located on the shoulder and backslopes positions were classified as Calcic Haploxeralfs and Vertic Haploxeralfs, respectively. Well-developed argillic horizons as indicators for higher degrees of soil evolution were observed in more-stable areas under the natural forest or less disturbed areas. Clay lessivage through these soil profiles have led to formation of Typic or Calcic Haploxeralfs, while under croplands (CP) were classified as Typic Calcixerepts. Conversion of sloping deforested areas to CP along with inappropriate management have accelerated soil erosion, resulting in unstable conditions in which decalcification and formation of developed soils cannot occur. Paddy cultivation in flat areas has caused to reduced conditions and formation of Typic Haplaquepts. Because of unfavorable conditions for chemical weathering (e.g. lower water retention compared to more-stable areas) no vermiculite was detected in the CP. The results showed that evolution and classification of the studied soils were strongly affected by land-use type, topography and management.

Keywords】Soil classification; Clay mineralogy; Land-use change; Topography; Loess