Long-term vegetation restoration increases carbon sequestration of different soil particles in a semi-arid desert

Vegetation restoration in desert areas has an important influence on soil carbon sequestration. To understand the long-term effects of vegetation restoration on soil particle composition and carbon sequestration of different soil particles in semi-arid deserts, we collected the topsoil of different types of vegetation restored for different periods at the southeast margin of Mu Us Desert and analyzed the soil organic carbon (SOC) and soil inorganic carbon (SIC) contents in soil particles of different sizes. The results demonstrated that after vegetation restoration, soil particles of <0.05 mm and aggregates in arbor lands and shrub lands increased 8 and 4 times and 4.67 and 4 times than shifting sandy land (CK), respectively. The SOC and SIC in different soil particles under vegetation increased with the restoration period. Among different vegetation forms, arbor land had significant effect on SIC fixation. Soil particles of <0.05 mm contained the highest SOC and SIC contents (16.8 and 0.78 g/kg), followed by aggregates (8.26 and 6.79 g/kg), 0.05-0.25 mm (8.24 and 4.55 g/kg), and >0.25 mm (5.23 and 2.25 g/kg). As for total SOC storage, it was positively correlated with the organic carbon storage of <0.05 mm particles. We concluded that SOC and SIC of <0.05 mm soil particles and aggregates increase with the restoration period and play a leading role in soil carbon sequestration. From the perspective of long-term soil carbon sequestration, the best vegetation restoration mode in Mu Us Desert would be arbor forest.