Claus-Thomas Bues

Radial Growth Dynamics of Spruce (Picea Abies) Measured by Micro-Cores

Using medical cannulas of 0.5 mm inside diameter, micro-cores were taken at three circurnferential heights from five spruce trees [Picea abies (L.) Karst.] in the Ore Mountains (Germany). The micro-cores were taken every second week during the growing seasons of 1996 and 1997 and light-microscopy studies were made on the micro-cores. The number of xylem and phloem cells, and total cell count in the cambial zone, were tabulated for each sampIe. Determination of the intra-annual cellular growth rate of conifers is simplified and will be possible also in long-term experiments. Preliminary evaluations of the wound response indicate that this micro-coring technique causes minimal injury.

Holzeigenschaften stark immissionsgeschädigter Fichten (Picea abies [L.] Karst.) in den Hochlagen des Osterzgebirges

ZusammenfassungIm Rahmen eines vom Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie (BMBF) ausgerichteten Verbundprojektes “Untersuchung von Waldökosystemen im Erzgebirge als Grundlage für einen ökologisch begründeten Waldumbau” war im Hinblick auf die weitere Anbauwürdigkeit und waldbauliche Behandlung die Frage nach den Holzeigenschaften der Baumart Fichte gestellt.Im Holz von durch SO2-Immissionen stark geschädigten Altfichten wurden in weniger als 0,5 mm breiten Splintholzjahrringen eine Verringerung der Tracheidenlängen und abnehmende Frühholzzellumina gefunden. Das Spätholz war durch abnehmende Zellwandstärken und flachere Mikrofibrillenwinkel in der Zellwandschicht S2 charakterisiert.Die anatomischen und strukturellen Merkmale des Holzes schmaler Jahrringe wurden sowohl in stark immissions-geschädigten Bäumen als auch in Bäumen mit vergleichbar schmalen Jahrringen auf unbelasteten Standorten gefunden.Festigkeitsuntersuchungen in Form von Werkstoffprüfungen nach DIN zeigten normale Festigkeitswerte in sekundär unbeeinflußtem Holz. Untersuchungen an besonders kleinen Prüfkörpern (Dynstatprüfungen) bestätigen bis zu einer minimalen Jahrringbreite von 0,4 mm die bekannten Beziehungen zwischen Rohdichte und Schlagbiegefestigkeit.Somit kann das Holz von Fichten aus den Hochlagen des Osterzgebirges uneingeschränkt verwendet werden.AbstractThe question for the wood properties of the tree species in regard to its further worthiness of cultivation and silvicultural treatment has been raised within the framework of the joint project “Investigations of Forest-Ecosystems in Erz Gebirge as a basis of a Forest Reconstruction by Ecological Criteria” undertaken within the framework of the Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie (BMBF) (Federal Ministry of Education, Research, and Technology).A decrease of tracheid lengths as well as of the lumina of early wood has been ascertained in sapwood annual rings smaller than 0.5 mm in width of mature spruce, the wood of which having been subject to heavy damage due to SO2 pollution. The late wood was characterized by decreasing cell wall thickness and larger microfibril angles within the cell wall layer S2. The anatomical and structural features of wood distinguished by narrow annual rings have been found both in heavily pollution-damaged trees as well as in trees with comparably narrow annual rings of non-polluted sites.Strength investigations in terms of materials testing according to DIN yielded normal strength values of wood that was not affected by secondary agents. Investigations on particularly small test specimens (Dynstat examinations) up to a minimal annual ring width confirm the known relationships between wood density and impact bending strength. Thus, the wood of spruces growing in the high-altitude belts of the eastern parts of Erz Gebirge may be used without reservations.

Effects of aging on wood: a literature review

Knowledge of wood aging and the property changes of aged wood compared with recent wood are crucial for conservation of wooden cultural heritage objects and historic buildings constructed of wood and also for the reuse of old construction wood. Therefore, a thorough literature review is presented about the different aspects of wood aging to provide a database for further investigations. One focus lies on the different kinds of aging: natural aging under aerobic and anaerobic storage conditions in contrast to accelerated aging under heat treatment. Further, influencing factors like wood treatment and long-term loading on the aging process are discussed. Property changes of naturally aged wood that has been stored under aerobic conditions are also researched. The resulting chemical, physical, and mechanical changes are thus discussed as well as any changes in color.

Wood Anatomical features and chemical composition of Prosopis kuntzei from the paraguayan chaco

Anatomical features for Prosopis kuntzei Harms were studied by light and scanning electron microscopy. The wood is mainly diffuse-porous with indistinct growth ring boundaries. Vessel diameter ranges between 11 to 193 μm. The thick-walled fibres average 1275 μm in length. Parenchyma bands are 66 to 1066 μm apart. Heartwood extractives were studied in the vessels, rays and part of the fibres by means of scanning UV microspectrophotometry. The pyrolitic lignin content is 30.7%. The percentage of polyphenolic compounds, such as flavonoids, hydrolysable tannins and proanthocyanidins, is comparatively high at 5.8%. Total extract contents were determined after organic solvent extractions (23.2%) and water extractions (24.9%). The FTIR spectroscopy showed nearly identical spectra for the methanol and water extracts, with characteristic absorption bands for aromatic substances at 1615 and 1520 cm-1. The spectrum of the acetone extract differs only due to an additional but distinct absorption in the carbonyl range at 1695 cm-1. GC/MS analyses revealed that in the acetone and methanol extracts, tetrahydroxy-flavan-3-ols (isomers of catechin and epicatechin) were the main constituents with a ratio of 25.3 and 27.6%.

Longitudinal penetration of silicon dioxide nanosols in wood of Pinus sylvestris

For purposes of wood preservation, stabilization and fire protection, the penetration ability of bio-inspired environmentally friendly Sebosil® nanosols in axial direction of the pine tracheids were investigated using macroscopic evaluations and EDX microanalysis.