Expansion of the Laboratory for Dendrochronology at CEZA into an international research archive

Report

By funding the project “Securing and Archiving the Hohenheim Tree Ring Collection”, the Klaus Tschira Foundation laid the foundation for the Laboratory for Dendrochronology at the Curt Engelhorn Center for Archaeometry (CEZA). With a further three-year grant, the foundation has been supporting the expansion of the laboratory into an international research archive since January 2023.

The Hohenheim tree ring collection is one of the world’s oldest and most renowned climate archives and consists of about 35,000 wood samples. The historical, archaeological and subfossil woods (cores and slices) are a few centimeters thick and have diameters of up to one and a half meters. They come mainly from Germany, but also from other parts of Central Europe. Some of them are thousands of years old. The special thing about them is that their annual ring patterns allow conclusions to be drawn about the climate of their growth period.

It took six years to move the approximately 3,000 boxes to Mannheim, Germany, to the CEZA and to create a physical dendrochronological archive. Here, the wood samples are now stored adequately, newly and properly packaged. In the newly established dendrochronological laboratory, researchers will determine the age of the samples and reconstruct earlier climatic and ecological developments.

To make this possible, the wood samples are now being viewed, processed and catalogued. In addition, a uniform digital database system is being set up – a task that will take some time, as the Hohenheim data are still largely available as index cards or text files.

Why dendrochronology?

Dendrochronology is the only scientific method that allows the age of subfossil and historic wood to be determined to the nearest year. It has therefore been used extremely successfully for decades in many areas of archaeological-art historical and geoscientific research for the calendrical dating of wood. Dendrochronology is one of the most versatile and useful dating methods and can provide important clues to the geographic origin of wood, providing complementary information on timber trade and trade routes. In addition, dendrochronology more broadly is a significant research method for reconstructing past climatic and ecological trends. It is an integral part of paleoclimatology for studying the climate dynamics of past times.

Based on the tree ring pattern, i.e. the sequence of narrow and wide rings of the wood, dendrochronology can determine the age of archaeological finds containing wood remains. Such material analyses are not only of interest to state archaeological offices – for example, when it comes to determining the age of paintings, sculptures or musical instruments to find out whether they are originals or forgeries. In addition, tree-ring analysis has established itself in building research as an extremely precise dating method of buildings and their history (origin, additions or alterations, repairs or repairs).

The measurement of tree rings not only enables the precise determination of the age of wood, in some cases to within a season, but also the linking of climatic data. Using so-called tree-ring chronologies, which also include the South German Chronology compiled by means of the “Hohenheim Tree-Ring Collection”, correlations between the climate and the growth of trees are investigated – for different types of wood and regions. In this way, the scientists reconstruct the climate of the last millennia.

Figures, data, facts

• Accompanying documents on paper: approx. 80 file folders
• Uncataloged and archived wood samples: ca. 4,000
• Unsorted entries without metadata: ca. 2,000-4,000
• Entries to be checked for consistency, completeness, and accuracy in previous database PINE with Excel lists: ca. 35,000
• Metadata available on index cards: approx. 5,000
• Measurement series to be digitized that are available on paper: approx. 3,000
• Data on floppy disks: approx. 1,150 (3.5 and 5.25 inch)
• Sorting images: approx. 40,000
• Cataloging of unnamed images: approx. 10,000