An Aarhus University oak tree felled during a campus expansion has become the centrepiece of a permanent exhibition linking the institution’s history with climate change and the nuclear tests of the 1950s. The large cross-section is now displayed in Stakladen, a venue in the university park, where its growth rings form a timeline of environmental and human events.
The oak had stood in the University Park for decades before it was cut down in 2020 to make room for the expansion of the campus. Archaeology professor Felix Riede preserved a section of its trunk and worked with researchers in archaeology, history, geoscience and physics to examine it.
The resulting Aarhus University exhibition presents the tree as both a natural record and a witness to the development of the university around it.
The Aarhus University oak tree records more than its age
Each visible ring represents one year of the oak’s growth. Differences in their width reflect the conditions experienced by the tree, including changes in temperature and other environmental factors.
Some parts of the trunk also correspond to moments in the history of Aarhus University, including the construction of the new University City and the first Regatta, one of the campus’s best-known student events. The exhibition places these institutional milestones alongside broader developments such as rising global temperatures.
The rings also contain traces associated with the atmospheric nuclear tests conducted during the 1950s. Above-ground nuclear explosions released large quantities of radioactive carbon into the atmosphere, creating what researchers call the bomb pulse. This increase in carbon-14 was absorbed by plants and preserved in wood formed during those years.
Research involving Aarhus University scientists has used Danish oak samples from 1954 to 1970 to study the bomb pulse and variations in atmospheric carbon-14. This makes trees from the period valuable archives of changes that occurred far beyond their immediate surroundings.
How tree rings become a historical barcode
The method used to analyse and compare annual growth rings is known as dendrochronology. Researchers measure the distinctive sequence of wider and narrower rings created by changing growing conditions. When patterns from different trees overlap, they can be matched and placed within a precise chronological sequence.
Riede described this pattern as a unique “barcode” produced by the conditions experienced during a tree’s lifetime. Oak is particularly useful because it generally produces clearly distinguishable annual rings.
Across Europe, researchers have connected living trees with timber recovered from ships, buildings, ancient fences and signposts. Bog oak and trunks preserved in landscapes that were later flooded have extended these overlapping sequences back several thousand years.
The section from the Aarhus University oak has now been added to this wider chronological record. It therefore belongs to a scientific archive that reaches far beyond the lifetime of the tree or the history of the campus.
A university history told through its environment
The exhibition originated from a proposal selected in a competition organised by Aarhus University’s climate initiative. The Aarhus University Research Foundation funded the work required to transform the oak section into an exhibit.
Researchers involved in its analysis came from several university departments, while specialists from Moesgaard and the Technical University of Denmark also contributed expertise in dendrochronology and physics.
This interdisciplinary approach changes the function of the felled tree. Rather than surviving only as a campus memory, it now connects local history, environmental change and scientific measurement in a single object.
Aarhus University rector Brian Bech Nielsen said the rings offer a way to reflect on the climate, the university’s development and the place of individuals within a continuing history. For former and current students, the oak may also recall everyday experiences in the University Park, from walking along its paths to studying beneath its trees.
The exhibition shows how an apparently ordinary part of a landscape can preserve evidence produced at very different scales. A tree that once recorded the conditions of a Danish university park now also forms part of a European chronology of climate, archaeology and human activity.
