Chemical composition and ultrastructure of a fossil wood from the genus of ancestral sequoia

Abstract

Go U~:ar, C. G. Staccioli, M. StollTwo well preserved stems of fossil sequoiadendron giganteum excavated in Turkey were studied using electron microscopic and chemical methods.Chemical analysis included determination of main constituents (lignin, cellulose, polyoses) as well as detailed analysis of extractives recovered with different solvents and applying e.g. FTIR, GC, GC-MS techniques. Special attention was paid to the determination of free and ester-bonded acidic groups. The results suggest that the in situ autohydrolysis could have been the major mechanism of degradation which, however, did not reach a very advanced state. The overall look at all the results, particularly at the ultramicroscopic pictures, leads to the assumption that this sample might be not as old as suggested by the common conclusions based on the beginning of the glacial period ( > 106 a). There could have been small ecological niches near the Mediterranean sea where sequoia species were able to survive several glacial and interglacial periods. Two independent determinations in Italy and Germany using the ~4C-method limited the age at 41,000 years or higher. Chemische Zusammensetzung and Ultrastruktur des Holzes einer fossilen 5equoiadendron speciesAn zwei gut erhaltenen St/immen einer fossilen Sequoiadendron giganteum wurden elektronenmikroskopische und chemische Untersuchungen durchgeftihrt. Neben der Bestimmung der Hauptbestandteile Lignin, Cellulose und Polyosen wurden vor allem die Extraktstoffe untersucht, die mit verschiedenen L6semitteln isoliert und chromatographisch getrennt wurden. Freie und gebundene S~iuregruppen sowie der pH-Wert der verschiedenen Extrakte wurden bestimmt. GC, GC-MS und FTIR wurden eingesetzt, um einzelne Bestandteile zu charakterisieren. Die Ergebnisse deuten daraufhin, daft der haupt-s~ichliche Abbaumechanismus auf einer in situ Autohydrolyse durch freigesetzte S~iuregruppen beruht. Der Abbau ist allerdings nicht sehr weit fortgeschritten. Das l~it~t die Vermutung zu, day diese fossile Probe deutlich junger ist als die atlgemein akzeptierte Annahme des Aussterbens dieser Spezies mit dem Beginn der Eiszeit vor etwa 1 Millionen ]ahren vorgibt. Im retativ warmen Mittelmeerklima k6nnten einige Arten mehrere Eiszeitperioden fiberlebt haben. Die radiologische Altersbestimmung an zwei Instituten in Italien und Deutschland ergab einen unteren Grenzwert von 41 000 Jahren.

Evaluation of the Applicability of Conventional Methods for the Chemical Characterization of Waterlogged Archaeological Wood

“…Buried wood is subject to a number of decay processes which develop according to various mechanisms (Florian and McCawley 1977; Uçar et al. 1996; Sandström et al.…”

“…Buried wood is subject to a number of decay processes which develop according to various mechanisms (Florian and McCawley 1977;Uçar et al 1996;Sandström et al 2003), although those of biological origin are by far the most common. In particular, in permanent conditions of water imbibition and almost complete absence of oxygen, the decay is due to a bacterial-type attack (Björdal et al 2000).…”

“…This type of decay implies a series of structural modifications, mainly related to the chemical composition and morphology of wood (Kim and Singh 2000). In waterlogged conditions, the decay progresses by depleting the polysaccharidic components within the fibrillar texture from the lumen toward the middle lamella, while the lignin only undergoes a slight oxidative modification that leaves it quantitatively unchanged (Goldstein 1984;Shiffer 1987;Hedges 1990;Kim 1990;Rowell and Barbour 1990;Fengel 1991;Eaton and Hale 1993;Uçar et al 1996;Passialis 1997;Kim and Singh 2000). This loss of wood substance decreases density and increases microporosity and permeability, and the wood is bulked by water (Hedges 1990;Fengel 1991).…”

A New Method to Quantitatively Evaluate the Chemical Composition of Waterlogged Wood by Means of Attenuated Total Reflectance Fourier Transform Infrared (ATR FT-IR) Measurements Carried Out on Wet Material

“…This occurrence is due to a hydrolysis reaction of biological origin (action of bacteria and fungi, primarily soft rot), although phenomena of chemical origin are also possible. 1,–3 However, the evolution rate of these processes strongly depends upon the specific waterlogged environment, and often, times of the order of several centuries to thousands of years are needed.…”

“…Some attempts have been made in the past to use FT-IR for quantitative evaluations in the case of archeological material. 2,13 These attempts were often based on a single or few bands used as a reference, by means of simple linear regression analysis. However, such a univariate analysis could be inadequate to perform consistent evaluations, because of the overlapping of signals related to various substances, for instance, extractives or (most important in waterlogged wood) inorganic compounds that permeate the wooden tissue during burial.…”