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In this study, we determined carbon allocation and carbon stocks in the plant-soil system of different dune ecosystems in northeastern China. We quantified the species composition, above- and below-ground biomasses, and carbon stocks of three dune types (i.e. active dunes, semi-stabilized dunes and stabilized dunes) and their corresponding inter-dune lowlands (i.e. interdune lowlands of active dunes, interdune lowlands of semi-stabilized dunes and interdune lowlands of stabilized dunes) in the Horqin Sandy Land. The results showed that the succession series on interdune lowlands of the Horqin Sandy Land confirmed differences in species composition of the various dune types. Aboveground carbon (AGC) on the interdune lowlands of semi-stabilized dunes (33.04 g C/m(2)) was greater (P<0.05) than that on the interdune lowlands of active dunes (10.73 g C/m(2)). At the same time, the different dune types did not show any significant differences (P>0.05) in belowground plant carbon (BGC). However, the percentage of plant BGC in interdune lowlands of active dunes (81.5%) was significantly higher (P<0.05) than that in the interdune lowlands of semi-stabilized dunes (58.9%). The predominant carbon pool in the study dune ecosystem was in the soil. It accounted for 95% to 99% of total carbon storage. Soil organic carbon (SOC) was at least 55% greater (P<0.05) in the interdunes than in the dunes. Stabilized dunes showed at least a 37% greater (P<0.05) SOC content than active dunes up to a 1-m soil depth. Meanwhile, SOC content of interdune lowlands of semi-stabilized dunes was greater (P<0.05) than that of interdune lowlands of active dunes only up to a 20-cm soil depth. The dune ecosystem showed a great potential to store carbon when interdune lowlands of active dunes were conversed to interdune lowlands of semi-stabilized dunes, which stored up to twice as much carbon per unit volume as interdune lowlands of active dunes.