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The Memory of Trees

Freie Universität graduate honored with the German Research Foundation (DFG) Bernd Rendel Prize

Oct 09, 2014

Anhand von Baumjahresringen können Geowissenschaftler das Klima vergangener Jahrhunderte rekonstruieren.
Geoscientists can use tree rings to reconstruct the climate of past centuries. Image Credit: Fotolia / Alexander von Düren
Der diesjährige Bernd-Rendel-Preis geht an Mandy Freund, Absolventin der Freien Universität.
This year’s Bernd Rendel Prize goes to Mandy Freund, a graduate of Freie Universität. Image Credit: Mandy Freund

As witnesses to centuries of climate history, very old trees supply geoscience researchers with insight into the weather during bygone eras. Mandy Freund, a graduate of Freie Universität, used tree rings to reconstruct the European climate of the past in her master’s thesis.

She studied the past 400 years for flooding and drought periods in regions from Scandinavia to the Mediterranean. The meteorologist’s research work is now being recognized by the German Research Foundation (DFG), which has chosen her for this year’s Bernd Rendel Prize.

Freund finished her degree in meteorology at Freie Universität just a year ago – and she has already won her first award. The Bernd Rendel Prize is awarded annually to young geoscientists who make original contributions to research in the geosciences even before completing their doctorates. Freund, 27, is among those selected for the award. Climate reconstruction was the subject of her master’s thesis, which originated in a cooperative relationship between the Institute of Meteorology at Freie Universität and the Helmholtz Centre Potsdam – German Research Centre for Geosciences (GFZ).

Green “Weather Stations”

While the first weather station in Germany has only been logging climate information since 1781, very old trees store at least twice as much information on the climate. Geoscientists can tap into this knowledge by studying oxygen and carbon isotopes in the tree rings, Freund explains. “During photosynthesis, the tree opens the stomata, or pores, of the leaves, letting carbon dioxide in and releasing water vapor. At high temperatures and during dry periods, these pores close in order to prevent water loss. This means less carbon dioxide is absorbed into the leaf, so heavy carbon isotopes accumulate and are then deposited in that year’s tree ring.” Lighter carbon isotopes in the wood are an indicator of cool, wet weather instead.

The geoscientists call these tree rings a “climate archive.” Freund explains, “It is even possible to trace the precipitation conditions of past years based on the light and heavy oxygen isotopes that the tree has absorbed in the water taken in by its roots.”

Learning from Climate History

Her master’s thesis presents Freund’s observations on a geographic basis, offering insight into large-scale weather patterns in Europe. “Reconstructing flood and drought phases in Europe allowed me to draw conclusions about the distribution and frequency of weather patterns. For example, if it is much drier than usual in the Balkans, it is very likely that the British Isles and Scandinavia will experience a humid, cool summer,” she says.

After finishing her thesis, Freund went to Australia, where she started a doctoral program at the University of Melbourne. Her dissertation is also about climate reconstruction. Alongside tree rings, she is also looking at other “climate archives” such as coral and sediment. Freund is now returning to Germany for a short time to accept the Bernd Rendel Prize at the GeoFrankfurt international conference.

The award, which comes with 1,000 euros in prize money, is intended to allow the young scientists to participate in conferences and scientific congresses. “I would like to use the prize money to go to a summer school program on climate reconstruction that I wouldn’t otherwise be able to afford,” Freund explains. “That in itself is one reason I’m very pleased to receive this award,” she says.

Further Information

Mandy Freund, PhD Student, The University of Melbourne, Email: