Afforestation and reforestation are effective and ecological ways of mitigating elevated atmospheric carbon dioxide (CO2) concentration and increasing carbon (C) storage in terrestrial ecosystems. In this study, we measured the above-ground (tree, herbaceous plants and litter) and below-ground (root and soil) C storage in an aspen plantation (Populus davidiana) monoculture (PD), a larch plantation (Larix pincipis-rupprechtii) monoculture (LP), a pine plantation (Pinus tabulaeformis) monoculture (PT), a larch and birch mixed plantation (L. pincipis-rupprechtii and Betula platyphlla mixed) (MLB), and an apricot plantation (Armeniaca sibirica) monoculture (AS) under the Desertification Combating Program in Hebei Province, the northern China. The objective was to assess the effect of afforestation species on ecosystem C pools of different plantation types. Results showed that C storage of LP stand (258.0 Mg/ha) and MLB (163.4 Mg/ha) were significantly higher than the C storage in PD (45.5 Mg/ha), PT (58.9 Mg/ha) and AS (49.4 Mg/ha), respectively. Soil C was the main carbon pool of the ecosystem C storage in the five plantation stands, ranging from 31.4 Mg/ha to 232.5 Mg/ha, which accounted for 69.0%–90.1% of the total ecosystem C storage. The C storage in tree layer was about 5.2%–23.2% of ecosystem C storage. The herbaceous plants and litter layers contained 1.0%–6.0% and 1.5%–3.3% of ecosystem C storage, respectively. Our results suggest that tree species should be incorporated to accurately develop regional C budget of afforestation program, and also imply that substantial differences in ecosystem C stocks among plantation types can facilitate decision making on C management.