[Influence of ecosystem type on the formation mechanisms of iron oxide-associated organic carbon]

Soil is the largest active carbon reservoir in terrestrial ecosystems. The persistence of soil organic carbon (SOC) plays a central role in regulating global carbon cycle and climate change. Iron oxides, with their unique chemical properties, are among the most important mineral phases controlling SOC stabilization. We synthesized current understanding of the mechanisms and drivers of SOC stabilization mediated by iron oxides. We highlighted the association patterns between iron oxides and organic carbon (Fe-OC) across forests, grasslands, and croplands, and explored how biotic and abiotic factors regulate the formation, transformation, and stability of Fe-OC complexes. The capacity of iron oxides to stabilize SOC varies substantially among ecosystems. In agricultural soils, management practices and external organic inputs shape the carbon-binding potential of iron oxides. In forests, Fe-OC complexes tend to be highly stable and are influenced by root exudates and soil mineralogy. Grasslands exhibit more variable Fe-OC dynamics, controlled by multiple factors including climate, root exudates and soil types. Increased precipitation can intensify iron reduction and subsequently alter Fe-OC stability. These ecosystem-level differences arise from shifts in soil microenvironments and microbial communities driven by vegetation composition, temperature, moisture, and light. Vegetation regulates iron oxide surface reactivity and mineral-organic associations through the changes in soil pH, organic matter inputs, and root exudate chemistry, while microbial community structure further influences Fe-mediated carbon stabilization pathways. Future research should reveal the micro-scale mechanisms underlying the formation and persistence of Fe-OC and assess how climate change will reshape these processes. Advancing cross-scale integration-from mechanistic studies to quantitative modeling-will be essential for predicting the long-term stability of Fe-OC across ecosystems and its contribution to global carbon cycle.