Micromorphology of development of some loess-derived soils of western Golestan province along a climo-topo-biosequence

The aim of the present study, was the micromorphological investigation of development of some loess-derived soils of Golestan province along a climo -topo- biosequence, starting from lowlands in north and ending to forest uplands in south. Four soil profiles, situated in aridic, xeric and udic moisture regimes selected for this study were located at 20 to 400m elevation above sea level. Disturbed and undisturbed samples were taken for physicochemical properties and micromorphological studies. The studied soils in north-south direction were classified as Gypsic Aquisalids (pedon 1), Typic Haploxerepts (pedon 2), Typic Calcixerolls (pedon 3) and Typic Hapludalfs (pedon 4). The results showed that soils in xeric and udic moisture regimes, had higher clay. Alfisols with udic moisture regime and forest land use, were weakly acidic, but at the semiarid climate, gypsum and calcite accumulation caused an increase in pH. In Aridisols and subsurface horizons of Mollisols, crystallitic b-fabric was dominant. Whereas Alfisols showed striated-speckled b-fabric. Subangular blocky microstructure is dominant in Alfisols, Aridisols and Inceptisols. The granular and crumb microstructure were also observed in surface horizons of Mollisols. Moreover Mollisols, showed higher porosity. Quantitative microscopic studies were done using Image Tool software and image analysis techniques. From aridic to udic moisture regime more variation in porosity were observed. In soils of xeric moisture regime, various forms of pedofeatures including calcite and Fe-Mn coatings were observed. In soils of udic moisture regime, clay coatings and clay fragments were dominant. Gypsum pedofeatures were dominant in arid soils.