Iron addition to soil specifically stabilized lignin. (July 2016)

• Record Type: Journal Article
• Authors: Hall, Steven J.; Silver, Whendee L.; Timokhin, Vitaliy I.; Hammel, Kenneth E.
• Is Part Of: Soil biology and biochemistry. Volume 98(2016)
• Page Start: 95
• Page End: 98
• Publication Date: 2016-07
• Subjects: Carbon stabilization -- Iron -- Lignin -- Recalcitrance -- Redox -- Soil organic matter; Soil biochemistry -- Periodicals; Soil biology -- Periodicals; Sols -- Biochimie -- Périodiques; Sols -- Biologie -- Périodiques; Sols -- Microbiologie -- Périodiques; Bodembiologie; Biochemie; 631.46
• DOI: 10.1016/j.soilbio.2016.04.010
• Languages: English
• ISSNs: 0038-0717

Abstract

Abstract: The importance of lignin as a recalcitrant constituent of soil organic matter (SOM) remains contested. Associations with iron (Fe) oxides have been proposed to specifically protect lignin from decomposition, but impacts of Fe-lignin interactions on mineralization rates remain unclear. Oxygen (O2 ) fluctuations characteristic of humid tropical soils drive reductive Fe dissolution and precipitation, facilitating multiple types of Fe-lignin interactions that could variably decompose or protect lignin. We tested impacts of Fe addition on 13 C methoxyl-labeled lignin mineralization in soils that were exposed to static or fluctuating O2 . Iron addition suppressed lignin mineralization to 21% of controls, regardless of O2 availability. However, Fe addition had no effect on soil CO2 production, implying that Fe oxides specifically protected lignin methoxyls but not bulk SOM. Iron oxide-lignin interactions represent a specific mechanism for lignin stabilization, linking SOM biochemical composition to turnover via geochemistry. Highlights: Ferrous Fe addition suppressed mineralization of 13 C-labeled lignin methoxyls. Ferrous Fe addition did not affect total soil respiration. Mineralization rates of lignin methoxyls implied decadal turnover times.