Litter quality assessed by solid state 13C NMR spectroscopy predicts decay rate better than C/N and Lignin/N ratios

► 13C NMR data and C/N and lignin/N ratios were compared as functional indicators of litter quality. ► 64 litter types were decomposed under controlled conditions. ► The use of C/N and lignin/N ratios as descriptors of litter quality is limited to undecomposed materials. ► The same indices are unable to predict mass loss of already decomposed organic materials. ► A new index of litter quality from 13C NMR data provided a consistent improved prediction of litter decay rate.