Dendrochronology

Dendrochronology is a dating technique that exploits the annual growth increments of trees to provide a precise estimate of the age (or period since formation) of a wood sample.

New cells, forming a ring, are added to the outer part of a tree trunk during each growing season.The number, width and pattern of the rings from certain tree species can provide the age of a piece of wood as well as information on the climatic conditions during the tree’s growth.

During the development of radiocarbon dating it was discovered that there were discrepancies between radiocarbon and dendrochronological ages.

This led to a greater recognition and improved understanding of the variation in atmospheric radiocarbon production that takes place with time.  Furthermore, taking advantage of the precise age of each tree ring together with the associated radiocarbon measurement on the tree ring itself, a reliable method for calibrating radiocarbon dates was developed.

The Belfast tree-ring laboratory was set up in the 1968 and, led initially by Mike Baillie and Jon Pilcher and later David Brown, was instrumental in providing the tree-ring chronology for Western Europe. The dendrochronology and radiocarbon laboratories at Queens University Belfast have a significant legacy of working together, along with other international institutions, to provide data and develop the calibration curves used in radiocarbon dating.

M Baillie and J Pilcher sampling wood from the Ulster Folk Museum in the 1970s.

A bonus of constructing the tree-ring chronology was that if dendrochronologists used timbers from building or archaeological sites in the chronologies then the dates obtained would be of interest to historians and archaeologists.

Information relating to the environment can also be obtained from individual trees and sites, and large-scale events can be observed from regional and world chronologies.

Belfast Laboratory Dendro Dataset

Most of the tree-ring data in this dataset is Irish oak material; these can be bog oak, archaeological and building samples and modern material. There are also bog pine samples from Ireland as well as sundry samples used in Irish houses that are from Britain or the European mainland and America. The dataset also contains a large number of bog oak samples from England that make up the English prehistoric chronology.

Finally, there are samples from France. These primarily consist of modern material and samples from building, mainly from Northern France.

The raw data from the Belfast laboratory can be downloaded here:

Download raw data

4 Irish bog oaks from different sites

Further information about dendrochronology at QUB and the Belfast data can be obtained by contacting:

Mr David Brown
Research Fellow
School of Natural and Built Environment
Queen’s University Belfast

View David’s profile

Selected reading:
  • Baillie MGL. 1982. Tree-Ring Dating and Archaeology. Croom Helm.
    Baillie MGL. 1995. A Slice Through Time: dendrochronology and precision dating. Batsford.
  • Baillie MGL, Brown DM. 1995. Some Deductions on Ancient Irish Trees from Dendrochronology. In J. R. Pilcher and S. S. Mac an tSaoir (eds.) Wood, Trees and Forests in Ireland. Royal Irish Academy, pp. 35-50.
  • Brown DM, Baillie MGL. 2007. Dendrochronology and lessons learned from Irish examples. In E. M. Murphy and N. J. Whitehouse (eds.) Environmental Archaeology in Ireland. Oxbow, pp. 18-36.
  • Brown DM, Baillie MGL. 2012. Confirming the existence of gaps and depletions in the Irish oak tree-ring record. In proceeding of Word Dendro 2010. Dendrochronologia 30(2): 85-91.
  • Pilcher JR, Baillie MGL, Schmidt B, Becker B. 1984. A 7272-year tree-ring chronology for Western Europe. Nature 312: 150-2.

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