Changes in organic components for fallen logs in old-growth Douglas-fir forests monitored by 13C nuclear magnetic resonance spectroscopy

13C cross-polarization magic-angle spinning nuclear magnetic resonance (CPMAS NMR) spectroscopy was used tocharacterize heartwood from decaying fallen boles of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), westernhemlock (Tsuga heterophylla (Raf.) Sarg.), and western red cedar (Thuja plicata Donn). The sample decay classesIto V had been previously assigned based on field observations. Solid-state '3C CPMAS NMR spectra were analyzedto determine the proportion of C of the following chemical types: carbohydrate, lignin, aliphatic, and the sum of carboxylplus carbonyl. For both Douglas-fir and western hemlock, the proportion of carbohydrate C increased slightly in theearly stages of decay. This was followed by a substantial increase in lignin C, while carbohydrate C declined to about10% of total C. By contrast, the spectra for western red cedar generally showed little change with increasing decayclass. One exceptional sample of western red cedar class IV was highly decomposed, indicating complete loss ofcarbohydrate C, and some loss of lignin side-chain C. For all three species, signals from alkyl and carbonyl C wereweak, but tended to increase slightly with decomposition, most likely because of the selective preservation of waxesand resins (alkyl C), and oxidation. Accumulation of chitin was not observed, and there was little evidence for lignindecomposition or for formation of humic polymers. 13C CPMAS NMR offers a simple and information-rich alter-native to wet chemical analyses to monitor changes in organic components during decomposition of woody litter.