Alteration of gymnosperm and angiosperm lignin during decomposition in forest humus layers

In the present investigation an attempt was made to characterize lignin decomposition in three forest humus profiles by the examination of their contents of simple lignin‐derived phenolic compounds obtained from alkaline CuO oxidation. The total amounts of p‐hydroxybenzoic, syringic, vanillic, p‐coumaric and ferulic acids, p‐hydroxybenzaldehyde, syringaldehyde and vanillin were determined. The acid to aldehyde weight ratios of the syringyl and vanillyl units, the weight ratio p‐coumaric/ferulic acids and the weight ratios of syringyl and cinnamyl phenols, respectively, to vanillyl phenols were used for the characterization of the gymnosperm and angiosperm lignin in different stages of the decomposition process. The patterns of these parameters with depht point to a considerable decomposition and chemical alteration of the lignin molecule during biodegradation.