Transfer of the Hohenheim annual ring collection

It will find its new home in the Mannheim squares in D 6, 3. 50,000 pieces of wood fill around 3,000 chests, the first 300 of which, weighing more than five tonnes, arrived in Mannheim in May. A further 200 crates will now be delivered at the beginning of December. The important wood archive was created over decades at the University of Hohenheim and is therefore known as the “Hohenheim tree ring collection”.

The historical, archaeological and subfossil wood (drill cores and slices) are a few centimetres thick and have diameters of up to one and a half metres. They come mainly from Germany, but also from other parts of Central Europe. Some of them are thousands of years old. What makes them special: Their growth ring patterns allow conclusions to be drawn about the climate in which they grew.

The Curt Engelhorn Centre for Archaeometry (CEZA) is currently processing the existing measurements of tree ring widths and feeding them into a database. The aim is to secure wood and climate data from different eras for the long term and make it accessible for future research projects.

However, the dendrochronological laboratory at CEZA not only collects data that has already been recorded. “We are constantly preparing wood that has not yet been measured in order to make the annual rings clearly visible. This allows us to measure them with an accuracy of 1/110 millimetre,” explains Dr Thorsten Westphal, head of the laboratory. “The annual ring structure of the wood reflects the changing climatic conditions – and allows us to date wood of unknown age back to the last ice age, around 12,000 years ago.

Dendrochronologists can determine the age of archaeological finds containing wood remains based on the growth ring pattern, i.e. the sequence of narrow and wide rings in the wood. Such material analyses are not only interesting for state archaeological offices – for example when it comes to determining the age of paintings, sculptures or musical instruments in order to find out whether they are originals or forgeries. Tree ring analysis has also established itself in building research as an extremely precise dating method for buildings and their history (origins, extensions or conversions, repairs, improvements, etc.).

The measurement of tree rings not only makes it possible to precisely determine the age of wood, sometimes down to one season, but also to link climate data. Using so-called tree ring chronologies, which also include the South German chronology compiled using the “Hohenheim tree ring collection”, relationships between climate and tree growth are analysed – for different types of wood and regions. In this way, the scientists reconstruct the climate of the last millennia.