Mechanisms of Soil Organic Carbon Stabilization in Floodplain Soils
Soil Organic Carbon (SOC) stabilization is vital for soil health, fertility, and ecosystem function, especially in floodplain soils, where hydrological processes and sediment deposition constantly influence carbon dynamics. Stabilized SOC supports shoreline stability, plant productivity, and long-term nutrient cycling. To explore the role of organic matter chemistry in SOC stabilization, I conducted a lab experiment using 13C-labeled long-chain dicarboxylic acids (DCA) to trace microbial uptake of n-alkyl lipids in floodplain soils. The results show that long-chain hydrophobic compounds resist microbial decomposition, contributing to SOC’s intermediate stabilization by remaining in the soil longer. Microbial assimilation and recycling also play a key role in SOC persistence. My study examined how SOC is incorporated into microbial cells and later integrated into the soil matrix through microbial decomposition and sorption to mineral surfaces. This process, facilitated by the microbial carbon pump, enhances SOC stabilization. Another critical mechanism is the physical protection of SOC within soil aggregates. While aggregate formation is well understood in terrestrial soils, little is known about it in semisubhydric and semiterrestric environments. Through a lab experiment with 13C-labeled plant material, I demonstrated that SOC occlusion in macroaggregates is essential for intermediate stabilization, protecting it from rapid decomposition. Aggregate stability and turnover further influence SOC retention. My study highlights how aggregate durability affects SOC persistence, emphasizing the importance of stable aggregates in maintaining SOC stocks in floodplain ecosystems. Overall, this research improves our understanding of the chemical, biological, and physical processes involved in SOC stabilization, offering insights into carbon retention mechanisms in floodplain soils.
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