كاني شناسي خاك هاي با مواد مادري لسي در دو منطقه از استان گلستان (هوتن و گرگان)

Clay mineralogy of the soils formed on loess parent material in two regions of Golestan Province (Huttan and Gorgan)

The main objectives of the present study were to investigate the effects of climate and slope position on the clay mineralogy of soils with loess parent material in Golestan Province. Clay minerals with their unique properties are the sites for ion exchange for plants and also considered as the source of soil nutrients. The abundance of each clay mineral having specific property influences the overall properties of the soils. Two transects of 200 and 300m length in Huttan (Maraveh Tappe area) and Gorgan regions were studied. Hutan and Gorgan regions have aridic-thermic and xeric-thermic soil moisture and temperature regimes, respectively. By considering the different landforms, four pedons in Hutan region and five in Gorgan region were studied. Mineralogical analysis revealed that illite and chlorite were dominant in both regions. Kaolinite was in lower amounts in both regions and was mainly of inherited origin. In Gorgan region, however, higher amount of smectite detected was mainly attributed as the transformation product of mica. This could point to existence of a more favorable weathering conditions leading to the transformation of illite and also chlorite in Gorgan region. Different slope positions have affected the clay mineralogy mainly due to the erosion of the surface soil. This had resulted in the decrease in smectite content in the surface horizons of the shoulder position.