C-13 NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY WITH CROSS-POLARIZATION AND MAGIC-ANGLE-SPINNING INVESTIGATION OF THE PROXIMATE-ANALYSIS FRACTIONS USED TO ASSESS LITTER QUALITY IN DECOMPOSITION STUDIES

Proximate analysis is often used in decomposition studies to character ize the organic components of foliar litter. The percent weight residu e remaining after extraction by nonpolar and polar solvents and H2SO4 hydrolysis (Klason lignin, KL) is commonly used as a measure of litter quality and a modelling parameter. While KL is associated with resist ance to decay, its nature is not well understood and it has long been suspected that it incorporates nonlignin components. We used solid-sta te C-13 nuclear magnetic resonance (NMR) spectroscopy to characterize litter, extracted residue, and the KL fraction of five species. NMR sh ows that cutin and condensed tannin are both significant components of litter and its extraction residues, in addition to lignin and carbohy drate, Hydrolysis with H2SO4 removes carbohydrates and amino acids, le aving the KL fraction derived from cutin, tannin, and lignin. Tannin r etention in KL was also demonstrated by a hydrolysis study of purified tannins and a brown-rot lignin, using both NMR and the proanthocyanid in assay for condensed tannins. Although the NMR results are qualitati ve at this stage, it is clear that KL has limited use as a parameter c ontrolling litter decomposition, and that other biopolymers should not be ignored in conceptual models, chemical analysis, and experimental design.