Global climate change and extensive socio-economic development together decrease ground cover in the semi-arid sandy grasslands of Horqin district in northern China and thereby increase the direct exposure of surface soil to erosion by strong winds—a process that ultimately converts the grassland into a sandy desert. Three ways to restore such degraded lands through afforestation were evaluated in terms of total carbon stored in the restored ecosystems compared to that in the control. Total carbon comprised that stored in the biomass of trees, herbs, and standing litter and in soil (up to a depth of 100 cm). The three restoration treatments were (1) enclosing the grassland within a shelter belt of Populus × beijingensis, (2) afforesting small but well-distributed patches within the grassland using Pinus sylvestris var. mongolica, and (3) similar afforestation using Ulmus pumila. Total ecosystem carbon storage increased significantly in all the three treatments over more than 20 years; at the end of that period, total ecosystem carbon was maximum (104.29 t/ha) in the grassland enclosed by the forest belt, followed, in that order, by afforestation with P. sylvestris (102.96 t/ha), that with U. pumila (92.24 t/ha), and the control (24.48 t/ha). The structure of the plant community created by these treatments is different from that found in natural stands of forest and in grasslands without trees or shrubs, and all the three treatments are suitable for restoring the moderately desertified sandy grasslands in south-eastern Horqin, northern China, depending on the availability of water and soil nutrients.