The Characterization of a Lignin-Derived Organic Matter Fraction in Soils Developed Under Different Vegetation Types

Abstract

1. Soil profiles developed under beech woodland, spruce woodland, pasture and arable cropping were analysed for total organic C and lignin derivatives extracted by CuO oxidation. This reaction primarily releases 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. 2. 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: equal amounts of syringyl and vanillyl residues; a low syringyl:vanillyl ratio; and 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. 3. 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.