Interactions of Hydrogeological Environments and Land Use Impact the Vertical Distribution of Soil Inorganic Carbon

Abstract

The heterogeneity of hydrogeological environments significantly influences carbon transport in terrestrial landscapes. Large-scale land-use changes disrupt hydrological processes and alter soil properties, consequently affecting the distribution of soil inorganic carbon (SIC). This study comprehensively analyzes the vertical distribution and controlling factors of SIC across one-meter profiles in various hydrogeologic units (HGUs) and land-use types (LUTs) from 100 soil profiles in the Sangong River watershed, Xinjiang, China. Our findings reveal that the alluvial-pluvial plain stores more SIC than the alluvial-pluvial fan at depths of 0–100 cm. Among land-use types, shrubland exhibits the highest SIC stock (SICD) in the topsoil (0–20 cm), while cropland shows greater SICD in deeper layers (20–60 and 60–100 cm). Importantly, HGUs significantly influence SIC distribution at depths of 0–20 and 20–60 cm, whereas the effect of LUTs on topsoil SIC is less pronounced, suggesting a dominant role of hydraulic connectivity and pedogenic processes. In contrast, LUTs significantly influence SICD in the subsoil (60–100 cm), with HGUs having a diminished effect. These results underscore the complex interplay between hydrogeological conditions and land use in shaping SIC distribution, particularly highlighting that the hydraulic connectivity governed by HGUs weakens at greater depths. Understanding these dynamics is essential for predicting SIC behavior and soil carbon balance in dryland ecosystems amidst evolving land-use and hydrological conditions.