Background Vegetation restoration in arid regions is a key strategy to combat desertification and land degradation, with shrub planting playing a crucial role in enhancing regional ecological stability and carbon sequestration. The Kerqin Desert, located in the northern part of China, is a typical arid region where vegetation restoration efforts have significantly improved the ecological environment. However, there is a lack of systematic research on the differences in carbon pool distribution and carbon sequestration functions across different shrublands.

Methods This study selected four shrub species (Artemisia halodendron, Corethrodendron fruticosum, Caragana microphylla, and Salix gordejevii) from the vegetation restoration area around the transmission tower bases in the Kerqin Desert to systematically analyze the vertical distribution characteristics of aboveground and belowground biomass carbon, soil organic carbon, and inorganic carbon, along with their main influencing factors.

Results 1) The study revealed pronounced interspecific variation in both aboveground and belowground biomass carbon among the four shrub species investigated. S. gordejevii plantations sequestered the greatest total biomass carbon, with aboveground and root pools reaching (2 233.48 ± 116.70) g/m² C, whereas the smallest root biomass carbon pool was recorded under A. halodendron at (422.43 ± 10.96) g/m² C. In all but C. fruticosum, aboveground biomass carbon exceeded that of roots by a statistically significant margin, underscoring species-specific carbon allocation patterns. 2) Soil carbon stocks likewise varied markedly among shrublands. The highest surface-soil organic carbon (OC) and inorganic carbon (IC) stocks were found under A. halodendron, at (249.44 ± 14.58) g/m² and (750.99 ± 33.37) g/m², respectively. In contrast, C. microphylla and S. gordejevii plots exhibited relatively lower soil carbon pools. When compared to adjacent unvegetated land, shrub establishment enhanced soil OC stocks by 66.20%−254.57% and IC stocks by 35.30%−146.45%, demonstrating the powerful role of woody cover in augmenting soil carbon reserves. 3) Depth-profile analysis showed a clear decline in both OC and IC with increasing soil depth: within the 0−40 cm layer, OC comprised 42.74%−49.87% of the total soil carbon pool, with deeper horizons contributing proportionally less. Finally, Pearson correlation analysis revealed that total soil carbon stock was strongly and positively associated with microbial biomass carbon, microbial biomass nitrogen, and the activities of alkaline phosphatase and β-glucosidase. In contrast, no significant relationship was detected between soil carbon stocks and root biomass carbon, suggesting that microbial processes may be more influential than root input in governing soil carbon accumulation under these shrubland systems.

Conclusions These findings suggest that vegetation restoration effectively increases soil carbon stock. Although plant-derived carbon is the primary contributor to these pools, the composition and stability of the microbial carbon pool are largely governed by microbial activity. This study provides important scientific and practical support for carbon sequestration and soil quality improvement in arid regions.