Tree rings and strontium point researchers to the origin of 400-year-old wood

Tree ring analyzes – so-called dendrochronological analyzes – have been part of archeology for many years and enable archaeologists to date old wooden objects very precisely. And in many cases they were also able to determine the origin of the wood.

But it has proved difficult for researchers to determine the origin of wood when the historical wood was imported from further afield to Denmark to serve as building material.

In a new study in the journal PLUS ONEAssociate Professor Aoife Daly and Dr. Alicia Van Ham-Meert from the University of Copenhagen show that combining analyzes of strontium and tree rings in wood can provide a more detailed picture of the origin of wood.

“Dendrochronology is a powerful tool for identifying the region of origin of historic wood. One of the potential biases in the method is using a dataset that inherently has a history of transportation and reuse. This phenomenon is clear, for example, when wood comes from different sources, particularly in urban centers. This is where strontium comes in,” says Aoife Daly.

“Specifically, we took wood samples from three old houses in the Danish cities of Aalborg and Horsens. A good example is a sample from a house in Horsens, where dendrochronological analysis incorrectly indicated that the wood was Danish, but the strontium signature matched exactly with a location in southern Sweden, suggesting that the wood was from southern Sweden after Horsens and used to build the house there, which is not surprising since Sweden was then part of the Kingdom of Denmark, but it is important that we can distinguish the provenances of the objects found.”

Lively timber trade on the south coast of Sweden

At that time, Gothenburg was the central shipping port for the timber trade. However, the new results suggest that other ports were also involved in the very lively timber trade in the region:

“The fact that some of the samples are from southern Sweden is important because it tells us that the timber trade has spread to a much larger area than we previously thought. And the strontium signatures point to an area around the Göta River, which must have been an important transport route for the timber traders,” says Alicia Van Ham-Meert.

“This analysis now shows that through strontium isotopic analysis of dendrochronological samples we can confirm the provenance of traded timber and move on to building ‘clean’ regional chronologies for more accurate provenance analysis,” concludes Aoife Daly.