Abstract: Wetland soil organic carbon comprises organic fractions that differ in biological origin, decomposition stage, and stabilization status. The preservation of plant-derived residue carbon and the accumulation of microbial necromass carbon represent two important pathways for SOC formation and stabilization in wetlands. Lignin phenols and amino sugars are commonly used to characterize lignin-derived plant residue components and estimate microbial necromass carbon, respectively. We synthesized the contrasting patterns of these two source-related residue carbon components across different wetland types and clarified the major drivers. Their contents vary substantially among wetland types, but the differences cannot be attributed to any single environmental factor. Instead, they emerge from the combined effects of plant inputs, microbial processing, decomposition and mineralization losses, and physicochemical protection. Under low-temperature, persistently anoxic, and strongly peat-forming conditions, the decomposition of plant residues is constrained, thereby promoting their preservation. Meanwhile, continuous plant inputs provide substrates for microbial assimilation and subsequent necromass formation. Water-table fluctuations, alternating redox conditions, sedimentation, and anthropogenic management can modify these processes and thereby regulate the relative contributions of plant-derived residue carbon and microbial necromass carbon. Future research should integrate multiple biomarkers with complementary multi-proxy approaches to elucidate the formation, transformation, and stabilization pathways of biologically derived residue carbon in wetlands, thereby advancing our understanding of wetland carbon pool formation and its responses and feedbacks to climate change.

Key words: wetland, soil organic carbon, plant-derived residue carbon, microbial-derived residue carbon, distribution pattern, driving factor