Tree Rings Of Wood Research Articles

13C NMR analysis of cellulose samples from different preparation methods

Alpha-cellulose is a part of the wooden material that preserves isotopic composition during tree-growth, and therefore provides important indirect data for paleoclimatological studies. For this reason, it is exceptionally important to extract the alpha-cellulose component from plants, e.g. from tree rings of wood. Since the cell wall of plant cells consists of multicomponent polysaccharides, the extraction of cellulose from wood is not an obvious task. In this paper, we describe, evaluate and compare nine methods, based on the literature and experimental observations, for obtaining cellulose from tree rings of wood. We show that the distortionless enhancement by polarization transfer (DEPT-135) variant of liquid-state 13C NMR spectroscopy is a powerful analytical method for monitoring the preparation process. Trifluoroacetic acid was applied as solvent for the NMR analysis. We proved that all the preparation methods give pure cellulose samples without hemicellulose and lignin content, and we propose methods resulting in non-fragmented cellulose. 13C and 18O isotope ratio measurements have shown that all the applied extraction methods result in similar isotope ratios, thus they are suitable for paleoclimatological studies.

A disastrous date

Paolo Cherubini and colleagues have demonstrated convincingly that the identification of olive wood tree-rings from Santorini is ‘practically impossible’. Thus, the single piece of evidence that might have persuaded some archaeologists to support the ‘high’ 1613±13 BC date for the Theran eruption is hors de combat. The Theran olive-tree branch has gone the way of the Greenland Ice Core results of similar date and which enjoyed a similar devoted following until shown to be from a different eruption. Taken with Malcolm Wiener's explicit exposé of the myriad shortcomings of 14C dating, especially for this time period and event, these results take us back to where we were before the ‘radiocarbon revolution‘, when the largest Holocene eruption in the ancient world happened as Minoan Crete enjoyed wideranging influence, perhaps even control, over the Aegean, when Late Minoan IA pottery styles proliferated, and Egypt was in the early stages of its New Kingdom period (Wiener 2012, 2013).