Chemical composition of the organic matter in forest soils: 1. Forest litter

The organic chemical composition of three different forest litter types (spruce, beech, ash) is characterized by comparing results obtained from (1) wet chemical degradations, (2) CPMAS¹³C NMR spectros-copy, and (3) pyrolysis-field ionization mass spectrometry (Py-FIMS). From CPMAS¹³C NMR spectros-copy, the litter layers consist of 17 to 23% alkyl-C, 52 to 56% O-alkyl-C, 15 to 23% aromatic carbon, and 5 to 10% carboxyl-C. The wet chemical methods account for 49 to 59% of the total organic carbon in the litter layers. More specifically, proteins and extractable lipids account for 30 to 40% of the alkyl-C. Polysaccharides and lignin side chains account for 74 to 78% of the O-alkyl-C, and lignin-derived phenols, determined by CuO-oxidation, account for 26 to 71% of the aromatic carbon. The identification of the organic litter constituents is substantiated qualitatively by Py-FIMS. All three methods give similar results for poly-saccharides, which make up 40 to 50% of the organic matter of litter. Furthermore, Py-FIMS indicates that part of the unknown alkyl-C is present in the form of bound, nonextractable fatty acids.