Changes in carbon and nitrogen storage along a restoration gradient in a semiarid sandy grassland

• We found a significant increase in C and N along the restoration gradient of sandy grassland.
• The highest proportion of C and N sequestration in the system is in the soil.
• Habitat restoration in sandy grasslands is associated with changes in ecosystem C and N.
• Species richness is associated with higher C and N storage in this sandy grassland system.

Understanding carbon (C) and nitrogen (N) pools in degraded ecosystems is useful to predict future C and N sequestration potential during restoration. Here we examined the distribution of C and N pools in plant–soil system at four successional stages: mobile dune, semi-fixed dune, fixed dune and grassland. The four stages reflect the successional sequence during sandy grassland restoration in Horqin Sandy Land, Northern China. C and N storage in plant biomass, litter and soil increased significantly with advancing sandy grassland restoration. With the conversion from mobile dune to semi-fixed dune, fixed dune and grassland, total ecosystem C and N storage increased by 1.9, 4.8, 7.1 and 3.3, 15.7, 20.6 times, respectively. More than 80% of C and N storage were stored in soil in sandy grassland restoration. C or N storage in plant and root biomass, litter and soil was positively correlated to species richness. Soil C and N storage was positively correlated to the C and N in plant and root biomass. These results suggest that sandy grassland restoration has a high potential to sequester C and N in the soil. Increasing plant production and species diversity via restoration likely enhance the C and N sequestration in sandy grassland ecosystems.