Ancient oak trees to shed light on the climate of the past 4,500 years

Researchers will soon be able to reconstruct the climate of north-west Europe including the UK over the last 4500 years, and to date wooden buildings and objects more accurately, by analysing the chemistry of ancient oak trees, through a new Swansea-led project just selected for €3 million in European funding.

Analysis of tree rings – known as dendrochronology - is an established scientific technique for understanding the past.  Tree rings can be examined in living or dead trees, or in objects made of wood, from the beams of a house to the planks of a ship. 

The width of the rings indicates how much the trees grew in a particular year, which not only tells us about the climate of the past, but also allows us to date wooden structures and objects from antiquity with extraordinary precision.   

However, this approach does not always work well in regions such as the UK and north-western Europe where the climate is mild and rarely limits tree growth. This makes dating challenging and reduces the confidence with which we can use tree-ring width measurements to study the climate of the past. 

This is where the new project, which is called QUERCUS (Latin for “oak”), will make a difference. 

The QUERCUS team will be examining ancient, historic and living oak samples covering the last 4500 years.  Oak trees are especially useful as they are widespread across the study region, live a long time and their remains are frequently found in the archaeological record. 

The key innovation is that the team will be analysing the chemistry of the wood rather than just the width of the rings.  They will be examining the stable (non-radioactive) isotopes of the fundamental elements: carbon, oxygen and hydrogen. 

The carbon isotopes in trees indicate changes in carbon assimilation for a given year, which in the UK relates to the amount of summer sunshine.  The oxygen and hydrogen isotopes record information on the water used by the tree which indicates the amount of summer rainfall and changes in large-scale atmospheric circulation.   

This evidence from the wood’s chemical signature will enable researchers to date the past and to reconstruct summer climate through time.  

Crucially, unlike ring width, these isotope signals are just as reliable in trees from areas where growth is not strongly limited by climate.  The project will also apply these methods to address long-standing archaeological questions of climate and chronology worldwide.   

The team, led by Professor Neil Loader of Swansea’s Department of Geography, includes scientists from the University of Oxford’s School of Archaeology. They will work in close partnership with an interdisciplinary team of experts including representatives of Indigenous groups from across Europe, Aotearoa/New Zealand and the USA.

Professor Neil Loader of Swansea University, who leads the QUERCUS project, said: 

“Stable isotopes in tree rings carry strong climate signals and can be used to reconstruct the climate of the past, even when the trees were not growing under environmental stress.  

Using this new technique, the QUERCUS project will develop the first annually-resolved tree-ring isotopic chronologies for the UK and north-western Europe, extending back 4,500 years to the Bronze Age.  

Our aim is to better understand the climate of the past, and for this we need an improved chronology of when things happened. Our ability to date wooden artefacts and timbers from antiquity will be enhanced significantly through this project. Together we hope that these advances will transform our knowledge of past climate and the dating of wooden artefacts and structures.” 

The funding for the QUERCUS project has been approved by the European Research Council (ERC).  Set up by the EU, the ERC funds top researchers of any nationality.  

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Notes to editors:

Swansea University is a world-class, research-led, dual campus university offering a first-class student experience and has one of the best employability rates of graduates in the UK. The University has the highest possible rating for teaching – the Gold rating in the Teaching Excellence Framework (TEF) in 2018 and was commended for its high proportions of students achieving consistently outstanding outcomes.

 

Swansea climbed 14 places to 31st in the Guardian University Guide 2019, making us Wales’ top ranked university, with one of the best success rates of graduates gaining employment in the UK and the same overall satisfaction level as the Number 1 ranked university.

 

The 2014 Research Excellence Framework (REF) 2014 results saw Swansea make the ‘biggest leap among research-intensive institutions’ in the UK (Times Higher Education, December 2014) and achieved its ambition to be a top 30 research University, soaring up the league table to 26th in the UK.

 

The University is in the top 300 best universities in the world, ranked in the 251-300 group in The Times Higher Education World University rankings 2018.  Swansea University now has 23 main partners, awarding joint degrees and post-graduate qualifications.

 

The University was established in 1920 and was the first campus university in the UK. It currently offers around 350 undergraduate courses and 350 postgraduate courses to circa 20,000 undergraduate and postgraduate students.  The University has ambitious expansion plans as it moves towards its centenary in 2020 and aims to continue to extend its global reach and realise its domestic and international potential.

 

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For more information:

 

Kevin Sullivan, senior press officer, Swansea University k.g.sullivan@swansea.ac.uk

 

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