Rcccntly, about 6,6(X) ycar old logs of Bischofia polycarpa wcrc rccovcrcd from thc rivcr-bcd of thc Yangtzc rivcr. Comparative studics havc bccn, thcrcforc. conductcd on thc constitucnts of bcn/cnccthanol cxtractivc“, Composition of carbohydratcs, and thc naturc of lignins in rcccnt wood and intact wood in thc ancicnt log“ of B. polycarpa. Thc major constitucnts of bcnzcnc-cthanol cxtractivcs from both woods arc found to be qualitativcly similar but quantitativcly diffcrcnt. Thc Composition of carbohydratcs in both woods is also found to bc qualitativcly similar but quantitativcly diffcrcnt. In gcncral, thc ancicnt wood contains somcwhat lese carbohydratcs than thc rcccnt wood. Thc major dif fcrencc is that xylan in thc lattcr contains a considcrablc amount of 0-acctyI groups whcrcas xylan in thc formcr docs not contain a dctcctablc amount of 0-acctyl groups. Thc naturc of millcd wood lignins (MWLs) from both woods has bccn charactcrizcd by mcans of chcmical analyscs and nC NMR spcctroscopy, Although both MWLs havc a similar guaiacylpropanc to syringylpropanc molar ratio, ca. 0.86:0.14, thc MWL from thc intact ancicnt wood has a Iowcr mcthoxyl and carbohydratc Contents but higher phcnolic and aliphatic hydroxyl contcnts, and a higher dcgrce of condcnsation than thc MWL from thc rcccnt wood. On thc basis of cxpcrimcntal data, it has bccn concludcd that thc changcs in thc chcmical composition of wood componcnts in thc intact ancicnt wood of B, polycarpa arc probably causcd mostly by slow in situ acid-catalyzcd hydrolysis and condcnsation of thc wood componcnts undcr thc anacrobic conditions and a slow concomitant diffusion-out of watcr-solublc low-molccular-wcight componcnts and dcgradation products from thc wood by thc rivcr-watcr throughout 6,600 ycars, during which thc logs wcrc dcpositcd in thc rivcr-bed of thc Yangtzc rivcr. © 1990, Walter de Gruyter. All rights reserved.
