Divergent responses of soil organic and inorganic carbon to edaphic factors within, but not between, shelterbelts and croplands in dryland of NW China

Background and Aim It remains unclear whether soil carbon fractions—organic (SOC) and inorganic (SIC)—exhibit distinct distribution patterns and responses to edaphic factors for shelterbelts and croplands due to their different management practices. Methods In total, we collected 480 soil samples (30 sites × 4 points × 4 depths) from 30 paired sites of shelterbelts (SF) and croplands (CF) in dryland, NW China. At each site, samples were taken from one SF point and three distance-based CF points (CF_0.25H, CF_0.5H, CF_1H) across four depths: 0–10 cm, 10–30 cm, 30–50 cm, and 50–100 cm. Results There was no significant ( P  > 0.05) differences in the content of soil total carbon (STC), SOC, SIC, and SIC:SOC ratio between SF and CF. A significant ( P  < 0.01) linear relationship existed between SOC and STC across depths. Both SOC and SOC:STC ratio were deceased significantly ( P  < 0.05) with increasing soil depths, but SIC was stabilized. Consistent findings from Pearson’s correction, Random Forest, linear mixed-effects model and structural equation model identified soil nutrients as the primary determinant of SOC, while physicochemical properties were the key driver of SIC. Variance partitioning analysis revealed that edaphic factors explained 78.19% and 70.10% of SOC variation, and 45.10% and 49.70% of SIC variation in SF and CF, respectively, suggests biotic factors (e.g. microorganism) may critically influence SIC accumulation in dryland soils. Conclusion Our study demonstrates contrasting responses of SOC and SIC to edaphic factors within shelterbelts and croplands, yet reveals consistent abiotic drivers governing soil C dynamics in both of them. These findings enhance understanding of soil C sequestration mechanisms and their abiotic controls in dryland agroforestry systems.