Abstract: Wetlands are highly sensitive to hydrological disturbances. The carbon source-sink dynamics of wetlands are jointly regulated by hydrological regimes and soil structural heterogeneity. Under frequent water-level fluctuations and wetting-drying cycles, complex pore architectures and heterogeneous flow pathways are gradually deve-loped in wetland soils, generating preferential flow processes that substantially deviate from the assumption of homogeneous continuum media. As rapid conduits for water and solute transport, preferential flows can modify soil carbon transformation by regulating the redistribution of water, the transport of oxygen, and the availability of carbon substrates within heterogeneous soils. We systematically reviewed the physical mechanisms, observation techniques, and simulation methods of soil preferential flow formation in wetlands, and analyzed the impact of preferential flow on carbon transformation by regulating water redistribution and oxygen transport. By integrating typical scenarios of tidal dynamics in coastal zones and water level fluctuations in riparian zones, we elucidated biogeochemical processes driven by preferential flow and highlighted the amplification effects of non-steady flow processes under extreme events. Future research should focus on hydro-biogeochemical coupling mechanisms in wetlands, advancing the synergistic development of multi-scale observations and model simulations to deepen understanding of carbon transformation processes in wetland soils under preferential flow influence. This would provide theoretical support for precise assessment of wetland carbon sequestration functions and the formulation of emission reduction strategies under climate change.

Key words: wetland, preferential flow, soil heterogeneity, soil carbon transformation, greenhouse gas