Long-term litter decomposition controlled by manganese redox cycling

Area of Science:

• Biogeochemistry
• Ecology
• Soil Science

Background:

• Litter decomposition is crucial for nutrient cycling, soil properties, and carbon balance.
• Traditional models focus on litter quality (e.g., lignin) but overlook other factors.
• A correlation exists between litter manganese (Mn) content and decomposition rates.

Purpose of the Study:

• Investigate the role of manganese (Mn) redox cycling in regulating long-term litter decomposition.
• Understand the microbial mechanisms involved in Mn transformation during decomposition.
• Determine the impact of Mn bioavailability on decomposition rates.

Main Methods:

• Long-term litter decomposition experiment (7 years).
• Analysis of Mn oxidation state and concentration changes.
• Chemical imaging of litter to track Mn redistribution.
• Correlation analysis between Mn species and organic matter breakdown products.

Main Results:

• Litter decomposition rates are tightly coupled with manganese (Mn) redox cycling.
• Microbes, particularly fungi, actively transform Mn(2+) to reactive Mn(3+) species at decay sites.
• Formation of Mn(3+) coincides with the generation of aromatic oxidation products, proving its role in litter breakdown.
• Mn accumulates as insoluble Mn(3+/4+) oxides over time.

Conclusions:

• Manganese (Mn) redox cycling is a key, previously underestimated, driver of litter decomposition.
• The plant-soil system's ability to manage Mn bioavailability and reactivity profoundly influences decomposition.
• Understanding Mn cycling is essential for accurate modeling of ecosystem processes and carbon balance.