Investigation of the quality and micromorphology of soil evolution in different landuses of a loess hillslope of Golestan province, a case study in Ghapan region

Rapid growth of population, and the consequent in creasing request for food, has resulted in the intensive cultivation and finally deterioration of natural covering of land surface, especially in forests. Soil quality is affected adversely as well. In order to study the effects of different land vegetation covers on soil quality attributes, a loess hillslope was selected in eastern Golestan province, Ghapan watershed. Four profiles in four land uses including Quercuse natural forest; Pinus plantation; Cupressus plantation and a cultivated land, were dug and studied. Samples from different horizons were collected for physico-chemical and microscopic analyses. Results showed that mean weight diameter of aggregates (MWD) was significantly different in the studied landuses and varied between 1.6 mm in Quercuse natural forest and 0.31 mm in cultivated land use. The lowest CEC, microbial respiration rate and organic carbon were 28.4 cmol kg-1, 177 μgCO2/g day and 1.32% in cultivated land use. Organic matter content in the forest area was considerably higher than that of the cultivated land use. Soil profile development studies revealed that forest soils were highly developed. Quercuse natural forest soils were classified as Calcic Haploxeralfs with a well developed argillic horizon unlike cultivated soils which showed the minimum development and classified as Typic Xerorthents. The soils of plantation had mollic epipedon and were classified as Typic Calcixerolls with moderate development. Micromorphological properties of soils can help consider changes in pedogenic processes occurring under different land covers. Formation of argillic horizon with speckled and some crystallitic b-fabric in the natural forest indicates to the high landscape stability. In contrast, crystallitic b-fabric of other land uses showed the absence of enough leaching of carbonate for the subsequent migration of clay particles. Intense erosion of the surface horizons of cultivated land use has resulted in the outcropping of the subsurface carbonate rich horizon preventing soil development.