Abstract: Plants are the key component of ecosystems in terms of matter exchange and energy flux. The aboveground and belowground biomasses affect carbon and nitrogen feedback processes differently in the plant-soil system. In this study, the plant characteristics, soil organic carbon (SOC), soil total nitrogen (TN), and their relationships were investigated in four different habitats in the Horqin Sandy Land; mobile dune, semi-fixed dune, fixed dune, and fenced grassland. These four habitats represent four consecutive stages of the restoration process. The results showed that plant aboveground biomass and belowground biomass varied among the habitats. Aboveground biomass initially increased and then decreased during the restoration process, while the belowground biomass showed an exponential increase during restoration. The root to shoot ratio was significantly higher in fenced grassland than in the other three habitats. Similarly to biomass, the length and surface area of plant roots significantly increased during restoration, but there was no obvious trend in the change in root volume, although it differed significantly among the four habitats. Both the contents and storage of SOC and TN increased during the restoration process. The contents of both SOC and TN were higher in the 0-10 cm soil layer than in the 10-20 cm soil layer, however, their rates of increase were higher in the 10-20 cm soil layer than in the 0-10 cm soil layer. Both the aboveground biomass and belowground biomass showed significant linear relationships with SOC and TN storage, while the regression coefficient was higher for belowground biomass than for aboveground biomass. From the perspective of plant root morphology, root length and root surface area were more strongly related than root biomass to SOC and TN. In conclusion, plant roots were more strongly related to SOC and TN than was aboveground biomass. Therefore, root activities may be an important factor for carbon and nitrogen accumulation in soil, especially in barren soils in environments with strong winds and sand-moving processes.