New light on old wood
The number of rings within a tree indicates its age, while analysis of those rings can also lead to new insights about wood and its provenance relevant to a wide variety of disciplines. We spoke to Professor Dan Hammarlund about his work as the coordinator of a research project dedicated to making dendrochronology data available to researchers.
The number of annual growth rings within a tree indicates its age, while analysis of those rings can also lead to deeper insights into the conditions and circumstances under which it grew. The width of the rings depends to a large extent on local climate conditions at the time of growth, such as precipitation levels, temperature and water availability. “Trees growing in the same area tend to show similar growth patterns. A harsh year and a good year could be lined up next to each other in a series of tree rings,” outlines Dan Hammarlund, Professor in the Department of Geology at Lund University in Sweden. This provides not just data on past climate conditions, but also other data relevant to a variety of disciplines, which Professor Hammarlund and his colleagues in the Old Wood in a New Light project are now working to bring together and make more widely available. “We want to make this tree ring data freely available to researchers across a wide variety of disciplines. In some cases researchers are well aware that tree-ring data are a good resource in their discipline, while others are not aware of their potential,” he says.
Tree ring data
Tree ring data are useful in reconstructing past climate conditions for example, while Professor
Hammarlund says it also holds wider relevance, such as in dating wood used in construction and determining its provenance. The project team, which brings together researchers at four laboratories across Sweden, has deep expertise in analysing tree rings and other wood features.
“We bring in cores or pieces of trunks and investigate different radii. We core both living trees and samples in standing constructions, while sometimes we can use a saw to sample
origin of a shipwreck isn’t clear, we can take out tree-ring series from the ship and perhaps also from the cargo. Then we can compare those ring series – if they are long enough - with reference series from different parts of Europe.”
Researchers have been able to show that certain ships sunk along the Swedish coastline originally came from Germany, and that these vessels were carrying wood from southern Poland, from which new insights can be drawn
“We want to make tree - ring data freely available to researchers across a wide variety of disciplines. In some cases researchers are well aware that tree-ring data are a good resource in their discipline, while others may not be aware of their potential ”
dead wood or trunks from archaeological excavations and other interesting sites. We can produce thin little cores, just a few millimetres in diameter, then analyse and measure the rings,” explains Professor Hammarlund. Researchers can also analyse samples of wood that have been used in construction.
“Timber constructions contain wood with the exact same structure as living wood, and we can determine their provenance,” continues Professor Hammarlund. “For example, if the
about trading relationships. The aim now for Professor Hammarlund and his colleagues in the project is to develop a database and make this type of data accessible to researchers and the wider public. “We want it to be easy for anyone to go into the database and search for what they are interested in,” he explains. The actual wood samples are available for people who are particularly interested, but the main focus is on bringing together data on samples from different regions. “We try to provide
both the environmental data and also the meta-data. People can also come to our labs and ask our team to date a sample. Ideally they provide details about where and when it was collected, and so we can then include the accompanying meta-data,” says Professor Hammarlund. “We want it to be easy for anyone to go into the database and search for what they are interested in,” he explains. So far, a lot of effort has been investigated into digitising meta-data, such as felling year, tree species, provenance and the function of the analysed timber. All this derived information, which is of great interest to researchers within cultural history, forestry, palaeoclimatology and a range of other disciplines, will be made freely and easily accessible in the database. This is not always the case with other sources of dendrochronology data, some of which are much more science-oriented. While it’s possible to download datasets made available in these systems by researchers, typically they don’t contain the metadata required to conduct more detailed investigations, which is a major priority in the project. “We aim to provide everything here that people require to conduct their research,” says Professor Hammarlund. This data can then inform research in a variety of different fields, including history and even the fine arts. “One member of the project team has been working with paintings, checking whether they are fakes. Historical paintings are highly valuable, and so people want to make sure they are authentic, and that they really do date from, for example, the 17th century,” outlines Professor Hammarlund. “One way of checking the age of these paintings is through assessing whether the boards really contain wood of the expected age. With tree ring series we can check whether these boards were indeed cut out in the 17th century, or if they are younger.”
Environmental studies
A further potential future application of dendrochronology data is in investigating the environmental background of contaminated sites. Analysis of tree rings can help researchers find out when a site was contaminated, as trees take up different chemical compounds and store them in their rings. “It’s then possible to produce graphs showing how much of the different heavy metals there are for example, and when they were taken up. This can be highly valuable in environmental investigations,” explains Professor Hammarlund. A lot of data have already been entered into the system, yet there is still more work to do, and Professor Hammarlund says there will always be scope for further additions. “We hope to extend the project to improve the database and add more information, but it will never really be complete, there will always be more that we can add,” he continues. “We have put a lot of effort into making the database sustainable, and have put a long-term maintenance plan in place.”
This is central to ensuring that the project has a lasting impact, beyond the conclusion of the funding term, and that researchers can still tap into this data in the future. The project team is working to improve and refine the database, and Professor Hammarlund says it will provide a valuable source of data for researchers.
“We have data series going back thousands of years, as we have tree-ring series from logs and stumps that have been preserved in oxygen-free environments, like in peat bogs, and at the bottom of lakes,” he says.
“We can pull these tree trunks or stumps up and they look more or less like they were cut down yesterday. We can easily analyse the rings, and they can be amalgamated into long time series’, from the present day back many thousands of years.”
iN a N EW ligHT
Project Objectives
The Old Wood in a New Light project is a Swedish initiative that aims to make data on wood and wood constructions available to researchers, which can then inform investigations across a wide variety of disciplines. Analysis of trees and tree rings can lead to fresh insights into how the climate has evolved, while determining the provenance of wood can help researchers reconstruct past trading relationships, just two examples of the wider importance of dendrochronology data.
Project Funding
The project Old Wood in a New Light is funded by an infrastructure research grant from Riksbankens Jubileumsfond, an independent foundation supporting research in the humanities and social sciences (grant no. IN20-0026).
Project Partners
• Lund University
• Stockholm University
• University of Gothenburg
• Swedish University of Agricultural Sciences
• Umeå University
Contact Details
Project Coordinator,
Dan Hammarlund
Professor of Quaternary Geology
Lund University
Faculty of Science
Department of Geology
Sölvegatan 12, SE-223 62 Lund, Sweden
T: +46 46 222 79 85
E: dan.hammarlund@geol.lu.se
W: www.lunduniversity.lu.se
W: www.geology.lu.se
The data are being made available through the Strategic Environmental Archaeology Database (SEAD: www.sead.se).
Old Wood in a New Light: An Online Dendrochronological Database in: International Journal of Wood Culture Volume 3 Issue 1-3 (2023) (brill.com)
Dan Hammarlund is Professor in the Department of Geology at Lund University, and has held research positions in Denmark and Canada. His research focusses on various aspects of environmental change based on chemical and biological analyses of lake sediments, peat sequences and tree-ring series.
