Distribution characteristics and relationships of soil organic carbon and inorganic carbon in a typical wetland in semi-arid area of Northeast China

The distribution characteristics and driving mechanisms of soil organic carbon (SOC) and inorganic carbon (SIC) are critical for understanding carbon sink functions in semi-arid wetlands. However, current research on SOC and SIC in these ecosystems remains insufficient. This study focused on the Momoge Wetland, a representative semi-arid wetland exhibiting three distinct hydrological connectivity patterns: floodplain wetlands (ET), irrigation district wetlands (ME), and isolated wetlands (WT). The wetland encompasses seven vegetation types and four salinity gradients. Through the analysis of relationships among soil physicochemical properties, microbial characteristics, SOC, and SIC, we identified the dominant factors influencing the distribution, stocks, and interactions of SOC and SIC in semi-arid wetlands. Our findings revealed significant spatial heterogeneity in SOC and SIC distribution within the 0–100 cm soil layer, which was primarily associated with variations in vegetation types, hydrological connectivity patterns, and salinity. The total SOC and SIC stocks in the 1-meter layer of the Momoge Wetland were 1.06 × 10⁷ Mg and 5.93 × 10⁶ Mg, respectively. The most important physicochemical soil factors affecting SOC and SIC content and density were TN and TCa, respectively. Microbial characteristics and soil physicochemical properties together explained 28.5 % of SOC variation and 22.9 % of SIC variation. SOC and SIC exhibited a complementary relationship; specifically, changes in hydrological connectivity patterns (ET → ME → WT) facilitated SOC-to-SIC transformation through multiple pathways, with varying intensities, by altering pH and salinity regimes and regulating plant characteristics, soil nutrients, and microbial characteristics. These results provide insights into soil carbon conversion and sequestration in semi-arid wetlands.