The characterization of a lignin-derived organic matter fraction in soils developed under different vegetation types.
Soil profiles developed under beech (Fagus sylvatica) woodland, spruce (Picea abies) woodland, pasture, and arable cropping in the UK were analysed for total organic C and lignin derivatives extracted by CuO oxidation. This reaction primarily released lignin-derived phenylpropanoid moieties from soil organic matter (SOM). The amount and composition of the moieties obtained provided a signature that was related to the origin of organic matter from particular soil horizons. There were clear differences between the lignin-derived phenylpropanoid signatures from similar depth horizons of soils developed under beech, spruce, and pasture. This was characterized by: (i) equal amounts of syringyl and vanillyl residues; (ii) a low syringyl:vanillyl ratio; and (iii) high concentration of ferulic acid, respectively, in the surface soil layers. The arable soil profile showed little differentiation in phenylpropanoid signature with depth (0-18 cm), presumably because of annual tillage. Further investigation into the degradation rates of individual phenylpropanoid moieties in soils and their adsorption onto soil fractions is required. A more extensive survey, characterizing the lignin-derived fraction in soils with a well documented land use history is also needed to establish a time scale for the translocation and degradation of the phenylpropanoid signatures of soils. Once calibrated, however, temporal changes in the composition of the lignin-phenylpropanoid SOM fraction will be potentially useful in monitoring the effects of vegetation and land management change on soil C cycling.