HR: 0830h
AN: B21C-0731    [PDF]
TI: Production of Hydrolysable Tannin-Like Structures During the Microbial Demethylation of lignin: An Assessment Using13C-Labeled Tetramethylammonium Hydroxide Thermochemolysis.
AU: * Filley, T
EM: filley@purdue.edu
AF: Department of Earth and Atmospheric Sciences Purdue University, 1397 Civil Engineering Building, West LAfayette, IN 47907 United States
AU: Blanchette, R
EM: robertb.umn.edu
AF: Department of Plant Pathology University of Minnesota, Dept Of plant Pathology 1991 Upper Buford Cr., Minneapolis, MN 55108 United States
AU: Nierop, K
EM: k.g.j.nierop@science.uva.nl
AF: IBED-Physical Geography University of Amsterdam, Nieuwe Achtergracht 166, Amsterdam, 1018 WV Netherlands
AU: Gamblin, D
EM: gamblind@purdue.edu
AF: Department of Earth and Atmospheric Sciences Purdue University, 1397 Civil Engineering Building, West LAfayette, IN 47907 United States
AB: Phenolic compounds in soils are important mediators of microbial activity, metal mobility, soil redox, and soil organic matter building processes. Direct tannin input and the microbial decomposition of lignin in litter and soil are important contributors to this pool of phenols. The ability to accurately assess the relative differences in lignin decay (which are initiated by demethylation and side chain oxidation) among synapyl, coniferyl, and p-coumaryl components of detrital lignin requires the ability to determine microbial demethylation within the complex soil residues. Differentiating between hydrolysable tannins and contributions from advanced lignin decay can be problematic for many of the most common molecular techniques such as alkaline CuO oxidation, pyrolysis GC, and tetramethylammonium hydroxide thermochemolysis because of either the masking effects of derivatizing agents, oxidative damage to ortho-phenols or low volatility of lignin monomers. In this study we investigate lignin demethylation and polyhydroxyl-aromatic production in BC and C horizons of sandy forest soils dominated by oak, the A horizon from a red spruce forest, and controlled microbial inoculation studies of woody tissue using in-line 13C-labeled tetramethylammonium hydroxide thermochemolysis. Both white-rot and brown-rot decay resulted in syringyl demethylation, with the latter exhibiting more aggressive demethylation chemistry, while coniferyl monomer demethylation was essentially restricted to brown-rot decay. In a typical brown-rot sequence demethylation of syringyl components occurs more rapidly than coniferyl units within the same tissue and lower molecular weight fragments are likewise more demethylated than lignin monomers containing the full glycerol side chain. Demethylation of both methoxyl groups in the syringyl monomer is evident in soil horizons as well as laboratory inoculations. The latter may suggest demethylation after lignin depolymerization. Low molecular weight syringyl and coniferyl monomers are from 25-50 % demethylated in surface litter and decrease in demethylation content with depth while unoxidzed lignin monomers with the full side chain exhibit little demethylation in surface horizons and increase in demethylation with depth. Application of this technique will greatly aid in the determination of soil organic matter cycling and the comparative roles and lifetime of hydrolysable tannins and highly altered lignin in soils.
DE: 1030 Geochemical cycles (0330)
DE: 1055 Organic geochemistry
DE: 4805 Biogeochemical cycles (1615)
DE: 4806 Carbon cycling
DE: 4815 Ecosystems, structure and dynamics
SC: Biogeosciences [B]
MN: 2003 Fall Meeting