effects of land use changes on soil organic carbon content in central region of karaj city

balance among different fractions of a carbon sources is of paramount importance in maintenance of very important in soil quality and environmental health. on the other hand, rapid growth of world population, degradation of agricultural soils, along with release of greenhouse gasses are some of the main challenges of the 21st century. the aim of this study was to investigate the extent of changes in land use that have occurred since 1955, their effect on carbon dynamics' and to study the effects of different land uses on organic carbon content in their different size fractions. twenty seven surface soil samples (0-20cm) were collected from different land use areas and physico-chemical analyses as well as physical size fractionation done on all. soil organic carbon content showed a decreasing trend in orchards, farms and rangelands respectively. urbanization and land use changes have prevented from dynamics and storage of 71273 and 190406 mgc/ha respectively.