Knowledge atlas Science

Dendrochronology

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In dendrochronology, the precise determination of the felling years of historical woods is made possible through the analysis of annual rings. Dendrochronology traces its origins back to Douglass (Arizona, 1908). Prof. Huber has adapted this field of research for European tree species and has further developed it. Since the 1930s, work has been carried out in this area in Tharandt. The research in dendrochronology and wood anatomy reveals the connection between climatic influences and the wood structure of trees (annual rings, density, and texture). The analysis of annual rings not only enables the determination of the age of wood samples but also forms the basis for insights into climate reconstruction and climate growth analyses. Dr. Björn Günther is also involved in age determination of wooden samples. His clients are both private individuals and public institutions, particularly in the fields of construction, monument preservation, and restoration. Samples range from assessments of construction wood renovation to determining the age of wood in musical instruments, and even extend to art-historical objects such as carved altars and picture panels. The dating certainty is always as good as the accuracy of the existing standard chronologies, so there can be no 100% dating certainty. Nevertheless, Dr. Günther can date about 75% of the submitted wood samples. These should have at least 50 annual rings for a reliable dating. The samples mainly come from the regions of Saxony, Thuringia, Brandenburg, and Franconia, as Dr. Günther must be on-site for the removal of a sample or the digital determination. Nationwide, in addition to laboratories at universities and other public institutions such as state offices, there are also various independent laboratories specializing in the age determination of historical woods. However, their numbers have been dwindling in recent years. In addition to unfavorable structural developments, financial aspects also play a role in this.

Name of Field in the local language
Umweltwissenschaften, Umweltanalyse, Forstwissenschaften, Hydrologie, Holz- und Pflanzenchemie, Holzanatomie
Area of Expertise
Dendrochronology
Scientists / Scientific team
Dr. Björn Günther, Technical University of Dresden, Faculty of Environmental Sciences, Department of Forestry has been a staff member since 2008 and has been involved in the establishment of the Environmental Analytics Equipment Center (CFEA) at the Faculty of Environmental Sciences since 2020/21. His main focus is on wood anatomy and dendrochronological research. In this context, he also deals with the age determination of historical wood samples. In the research area of dendrochronology, several working groups are active on different questions in various professorships, with about 20 employees involved.
Location, Institution, Website
The Department of Forestry Science is located in Tharandt near Dresden. The laboratories belonging to the Environmental Analysis Equipment Center are distributed across various locations, including Pirna and Dresden, and two locations in Tharandt, where the department is based.
Contact
Technical University of Dresden, Institute for Soil Science and Site Science D-01737 Tharandt, Pienner Straße 19. Dr. Björn Günther, phone: +49 351 463 31361, e-mail: bjoern.guenther@tu-dresden.de
Type of Institution
University

Laboratory and research space
Several laboratories at various locations in Tharandt, Dresden, and Pirna.
Materials and equipment
Tree and beam discs (cross-sections of woody plants) or drill cores of the wood parts to be determined. The processed species include oak, pine, fir, spruce, ash, beech, and partly also alder and elm.
Technology / Tools / Machines
Digital microscope, digital image analysis instruments. Preparing drill cores, grinding, scanning surfaces, analysis using digital image processing. Tree ring widths are also measured with a linear measuring table and microscope. Very soft wood surfaces are only cutted, not grounded.
Research Methods / Processes
Analysis of annual ring patterns. Determination of wood ages in all possible processing stages of the wood (e.g., musical instruments, construction timber, artworks) using non-destructive (digital or photos of wood cross-sections) technologies or by taking drill cores or wood discs. Creation of standard chronologies (time series of the year-specific average growth of a tree species of a specific region), which are extended and improved by each processed dating. It is always measured from the youngest to the oldest tree ring and a time series with annual ring widths is created. This time series is digitally compared with existing chronologies; where the highest synchronicity exists, the age determination is applied.

Most impactful project
For the standard chronologies, a large number of samples must be analyzed. In each case, the tree species and region with their specific conditions must be taken into account. For Saxony, several chronologies for spruces are necessary, so there are different chronologies for the western and eastern Ore Mountains. For firs, the data collection of a chronology sometimes covers the entire southeast of Germany. Cooperation with other laboratories is important to improve the range of standard chronologies and thus the dating certainty. In addition, the sampled wood structures could be analyzed more extensively to improve the accuracy of the chronologies, not only through better digital measuring instruments but also by including further wood atomic features, such as the measurement of cell structures. However, for the pure age determination of trees, the gain in knowledge for the user is rather low, so here costs would have to be weighed against benefits.