Supporting information_Soil carbon isotopes in global coastal wetlands

In this study, we synthesized date from global coastal wetland studies to reveal this scientific issue. The results indicated that soil δ¹³C exhibits significant spatial heterogeneity across global coastal wetlands, with values ranging from -21.20‰ to -9.00‰ and decreasing with increasing latitude. Within the soil profile (0-100 cm), δ¹³C values increased with depth. Significant variations in soil δ¹³C values were also observed among different vegetation types, with seagrass meadows and mudflats exhibiting significantly higher δ¹³C values compared to salt marshes and mangroves (p < 0.05). Climatic factors, such as mean annual precipitation (MAP) and mean annual temperature (MAT), were found to directly and indirectly regulate soil δ¹³C values. Specifically, MAP exhibited a significant negative correlation with soil δ¹³C values, while MAT showed a positive effect. Soil physicochemical properties were identified as the primary factors influencing soil δ¹³C values, with soil pH indirectly affecting the δ¹³C distribution by controlling clay content and total organic carbon (TOC). These results showed that the interactions of soil physicochemical properties, climate factors and vegetation types significantly influenced the spatial distribution of soil δ¹³C in coastal wetland ecosystems. This study will provide valuable scientific references for a deeper understanding of C biogeochemical cycles in coastal wetland ecosystems.