Lignin and fungal abundance modify manganese effects on soil organic carbon persistence at the continental scale

Plant‐Soil Relationships Influence Observed Trends Between Manganese and Carbon Across Biomes

“…We speculate that enhanced Mn uptake by woody plants could even have been developed as an adaptation to support lignin synthesis and/or to increase the decomposability of lignin-rich litter in the soil to facilitate nutrient readsorption. Indeed, the negative effects of Mn on C storage in mineral soils were most pronounced when soils contained lignin-rich organic matter (Possinger et al, 2022). Alternatively, woody plants may increase Mn solubility and uptake by acidifying the soil (e.g., Jobbágy & Jackson, 2003), or increased lignin deposition may serve as a Mn detoxification mechanism (Gao et al, 2012).…”

“…They propose that the net effect of Mn on C storage in mineral soils is dependent on biotic factors and organic matter composition. More specifically, Mn stimulates the decomposition of lignin‐rich C in mineral soils with a high proportion of fungi, but the effects of Mn enrichment on C storage and turnover are at least in part negated by enhanced stabilization of degradation products (Possinger et al., 2022). These results indicate complex interactions amongst site properties that may obscure simple correlations between Mn and C across diverse sites.…”

“…Differences in Mn content coupled to a variation in lignin content amongst plant species may complicate the observed effects of Mn on decomposition but have not been addressed. Possinger et al (2022) recently examined how correlations between Mn and organic C varied with soil organic matter degradation indices (e.g., C:N and amino acid:lignin ratios) and with fungal:bacterial ratios in mineral soils that span the continental United States, using data reported by the National Ecological Observatory Network (NEON, 2022) (Hinckley et al, 2016). They propose that the net effect of Mn on C storage in mineral soils is dependent on biotic factors and organic matter composition.…”

Microbial Necromass, Lignin, and Glycoproteins for Determining and Optimizing Blue Carbon Formation

“…In environments with high N availability, the growth of fungi and polyphenol oxidase activity is suppressed. , The higher AN content in low-salinity soils led to less oxidation of lignin, resulting in higher contributions of lignin to SOC. Conversely, GRSP with its better capacity in binding both mineral and organic particles exhibits a greater tendency to form stable aggregates compared to amino sugars and lignin .…”

Modeling Interactive Effects of Manganese Bioavailability, Nitrogen Deposition, and Warming on Soil Carbon Storage

“…Mn ions involved in reactions include divalent (Mn 2+ ) and trivalent (Mn 3+ ) species, with Mn 3+ existing in either a meta‐stable chelated state (formed in solution following Mn 3+ production by the MnP enzyme) or quasi‐instantaneously precipitating to birnessite. We consider only diffusible Mn 3+ bound to small organic molecules and do not include Mn 3+ ions that complex with solid‐phase organic matter (e.g., pyrophosphate‐extractable Mn (Jones et al., 2020; Possinger et al., 2022)). The availability of Mn 3+ for aqueous reactions is calculated using transition state theory rate laws implemented in PFLOTRAN (Dwivedi et al., 2018; Dwivedi et al., 2018; Lichtner et al., 2015; Lichtner et al., 2015, 2015) for kinetic precipitation/dissolution of birnessite, which is highly sensitive to pH due to the stoichiometry of the reaction: $$${I}_{m}=-{k}_{m}\left({1-\left({K}_{m}{\left[{\mathrm{H}}^{+}\right]}^{-21}{\left[\mathrm{M}{\mathrm{n}}^{3+}\right]}^{7}\right)}^{1/7}\right)$$$ where I m is the precipitation/dissolution rate (mol m −3 s −1 ); k m is the reaction rate constant (mol m −3 soil s −1 ); and K m is the equilibrium constant (10 −5.5 ).…”