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On Friday 11 July, Josue Susperregi Lasalde will defend his PhD dissertation ‘Development of a reference chronology for oak in the Basque Country to improve knowledge about its wooden heritage’. In his dissertation, Susperregi Lasalde establishes a reference curve for oak woods in the Basque Country, which can be used to study tree rings and to date wooden objects.

Dendrochronology

Dendrochronology is the study of tree-ring patterns. These rings contain key information about past times and they can tell us something about environmental change and the exact age of a piece of wood. By analysing tree rings, scientists can establish absolute dates (specific calendar years) and learn about the provenance of the wood.

Wooden heritage elements like ships, churches, palaces, farmhouses, barns, river dams, furniture, and art pieces can be studied using dendrochronology. To analyse these tree rings, a reference curve or chronology must be established for each wood type and climatic area. Developing this reference curve is a long process which involves collecting samples from old living trees and historical wooden structures within a certain area.

Oak woods in the Basque Country

In his dissertation, Susperregi Lasalde develops a reference curve for oak woods in the Basque Country. This region is located in the north of the Iberian Peninsula, and has remained largely unexplored in dendrochronological research until now. His research has taken more than 25 years, and the main results are presented in his dissertation.

Susperregi Lasalde's reference curve covers the last 800 years, and during its development all kinds of Basque wooden heritage items have been analysed. It is now possible to date historical wooden buildings and artefacts in the Basque Country with far greater accuracy than was previously possible.