USE OF 13C NMR AND FTIR FOR ELUCIDATION OF DEGRADATION PATHWAYS DURING NATURAL LITTER DECOMPOSITION AND COMPOSTING I. EARLY STAGE LEAF DEGRADATION

Abstract

Oxidative degradation of plant tissue leads to the formation of natural dissolved organic carbon (DOC) and humus. Infrared (IR) and ¹³C nuclear magnetic resonance (NMR) spectrometry have been used to elucidate the chemical reactions of the early stages of degradation that give rise to DOC derived from litter and compost. The results of this study indicate that oxidation of the lignin components of plant tissue follows the sequence of O-demethylation, and hydroxylation followed by ring-fission, chain-shortening, and oxidative removal of substituents. Oxidative ring-fission leads to the formation of carboxylic acid groups on the cleaved ends of the rings and, in the process, transforms phenolic groups into aliphatic alcoholic groups. The carbohydrate components are broken down into aliphatic hydroxy acids and aliphatic alcohols.