Effects of Climate Change on the Interaction Between Soil Organic and Inorganic Carbon in Global Drylands

ABSTRACT In dryland ecosystems, soil inorganic carbon (SIC) is as important as soil organic carbon (SOC), with both playing vital roles in carbon sequestration and ecosystem stability. However, most previous studies have primarily focused on the impacts of climate change on SOC, leading to a limited understanding of SIC dynamics and SOC‐SIC interactions. In this study, we integrated 1131 paired SOC and SIC observations from 169 sites across global drylands following vegetation restoration and investigated the effects of current and future climate change on the SOC, SIC, and the ratio of SIC to SOC (SIC/SOC). The results indicated that subsoil SOC (20–100 cm) in shrubs was significantly lower than in forests and grasslands, while the SIC/SOC was significantly higher. A significant positive correlation was observed between SOC and SIC ( p < 0.05). Along the precipitation gradient, the rate of SIC increase was 1.29 times greater than that of SOC in topsoils (0–20 cm) and 4.86 times greater in deeper soil layers (> 100 cm). Similarly, along the temperature gradient, the increase in SIC was 0.96 times greater than that of SOC in topsoils and 3.5 times greater in deeper soils. Structural equation modeling (SEM) revealed that climatic factors influence SOC, SIC, and SIC/SOC both directly and indirectly, with pH, total nitrogen (TN), and sand content serving as key mediating variables. Under different climate change scenarios, we observed a wide range of changes in SOC and SIC across soil depths, highlighting substantial uncertainty in predicting future SIC/SOC dynamics. Under the SSP126 scenario, SOC increased by 23.7%–66.6% across various soil depths, while SIC decreased by as much as 68.5% in the topsoil under SSP370. Our study highlights the importance of balancing SOC and SIC, advancing a comprehensive understanding of soil carbon dynamics, and providing critical scientific support for addressing climate change in dryland ecosystems.