Abstract: Soil organic carbon (SOC) and soil inorganic carbon (SIC) are both crucial components of soil carbon. In arid and semi-arid regions, there exist at least as much as or more SIC than SOC, and it has a great potential for reducing the rate of atmospheric CO₂ enrichment by increasing SOC and SIC sequestration. Studies involving soil carbon sequestration mainly focused on SOC in the first meter, or even shallower, and SIC was often neglected or underestimated. Revegetation, an effective method for controlling desertification and sequestrating carbon, has been wildly used in desert areas of China. However, knowledge about effects of revegetation on SOC and SIC distribution in both shallow and deep soils are still limited, as well as their relations with soil changes. In this study, we investigated the distribution of soil carbon from sand-binding areas established in 1964, 1981 and 1990 (Y64, Y81, and Y90), and adjacent moving sand dunes (Y0) in terms of concentration and density of both SOC and SIC along 0-3.0 m soil profile. The results showed that, in 0-0.1 m layer, SOC concentration increased from 0.29 g·kg^-1 of Y0 to 1.95 g·kg^-1 of Y64, and SIC concentration increased from 2.87 g·kg^-1 of Y0 to 4.19 g·kg^-1 of Y64. SOC concentration decreased as soil depth increased, while SIC concentration waved at a range of 2.44 g·kg^-1 to 3.31 g·kg^-1. The total SOC density in 0-3.0 m profile increased significantly from Y0 to Y64, and that in 0-0.4 m layer (0.18 to 0.52 kg·m^-2) increased faster than 1.0-3.0 m layer (0.80 to 0.88 kg·m^-2), thus the ratio of SOC density in 0-0.4 m layer (14.3% to 30.4%) significantly increased but that of 1.0-3.0 m decreased (64.8% to 51.6%). SIC density in 0-0.4 m and 1.0-3.0 m layer also increased from Y0 to Y64. According to redundancy analysis, soil fine particles (FPs), water availability (SWA), total nitrogen (TN), total phosphorus (TP), pH and electrical conductivity (EC) positively related to soil carbon density in 0-0.4 m layer, and these factors could explain 86.2% of variation in soil carbon density. The results of correlation analysis further showed that SOC density has significant positive relations with FPs, TN, TP, SWA and EC (P<0.001), while SIC positively related with all soil properties (P<0.05) except pH and EC. In addition, SOC density negatively related with soil water content in 0-3.0 m profile (P<0.01) and 1.0-3.0 m layer (P<0.05). Overall, our findings indicated that establishment of sand-binding vegetation are beneficial for accumulation of SOC and SIC in both shallow and deep soils, and changes of soil carbon closely related to soil properties.

Key words: moving sand dunes, sand-binding vegetation, soil organic carbon, soil inorganic carbon, soil properties