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Afforestation was one of most successful measures to rehabilitate desertified lands and to improve regional eco-environments in the Horqin Sand Land. A field experiment was conducted during 2005 and 2006 in the Horqin Sand land to investigate the effects of Populus simonii plantation growth on soil crust formation and topsoil properties. The results showed that plantation establishment promoted the development of biological soil crust and improved properties of topsoil 0-5 cm under the crust in sand dunes. As the plantation aged, soil crust developed gradually from a physical crust, to a lichen crust and then to a moss crust and crust coverage, thickness, hardness, very fine sand content, clay, silt, organic carbon and nutrients increased significantly. Clay, silt, organic carbon and nutrients in topsoil 0-2.5 cm and 2.5-5.0 cm under the soil crust increased with plantation age and crust development, but the magnitude of changes decreased with increasing soil depth. Changes in soil physical and chemical properties in the crust had a significant positive correlation with plantation age, and changes in physical and chemical properties in the 0-5.0 cm layer of topsoil had a significant positive correlation with soil crust development and plantation age. Soil crust development and changes in topsoil properties under the soil crust can be attributed primarily to the reestablishment of vegetation and the duration that the vegetation is in place. (c) 2010 Elsevier B.V. All rights reserved.