Seasonally flooded wetlands store soil carbon when plant inputs are preserved under slow decomposition, but several interacting constraints limit long-term stabilization. Researchers emphasize that waterlogged soils create reduced conditions that slow aerobic decay, yet repeated drying and rewetting, temperature shifts, and mineral interactions frequently prevent deep, persistent stabilization. William J. Mitsch Florida Gulf Coast University has long argued that hydrology is the primary control on wetland carbon balance, because alternating oxic and anoxic periods expose previously protected organic matter to rapid microbial mineralization. This makes seasonally flooded systems more vulnerable than permanently inundated peatlands.
Controls on stabilization mechanisms
The most direct limiter is redox fluctuation. When soils dry, oxygen penetrates and stimulates microbial decomposition, releasing CO2 and converting complex organic molecules into forms that are less likely to sorb to minerals. Robert D. DeLaune Louisiana State University has documented how sulfate and iron cycling under changing redox states alters the fate of organic matter in coastal marsh soils, with sulfate reduction and sulfide formation driving losses of organic carbon under certain salinity regimes. Mineral protection and aggregation can stabilize carbon where clay and iron oxides bind organic molecules, but frequent flooding cycles and root bioturbation break apart aggregates and reduce long-term protection. Temperature and seasonal plant productivity modulate inputs: warmer, longer growing seasons can increase litter inputs but also accelerate decomposition.
Consequences and human dimensions
Limits on stabilization have direct climate and social consequences. Carbon released from seasonally flooded wetlands contributes to atmospheric greenhouse gases and can undermine ecosystem services such as fisheries and soil fertility used by local communities. Simon L. Lewis University of Leeds emphasizes that conserving and restoring wetland hydrology is a cost-effective climate strategy, yet restoration choices involve trade-offs: rewetting can reduce CO2 losses but may increase methane emissions, creating complex policy decisions for land managers and indigenous peoples whose livelihoods depend on seasonal flooding patterns. Local cultural practices around agriculture and water management influence outcomes and must be integrated into restoration plans.
Addressing these limits requires protecting natural hydrological regimes, promoting conditions that favor mineral-associated carbon stabilization, and tailoring restoration to regional salinity, temperature, and social contexts. Evidence from wetland biogeochemistry and restoration science underscores that hydrology, microbial ecology, and mineralogy together determine whether seasonally flooded wetlands act as durable carbon sinks or transient reservoirs.