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Lady of the rings

In meticulous detail, the dendrochronologist Lisa Shindo records the annual growth rings of historic wooden beams and furniture to determine their age and origin, as well as the ecological and climatic conditions of the past in the region.

Woman takes samples from a wooden beam.
© Alexia Lattard

Using special tools, dendrochronologist Lisa Shindo takes small samples from the wooden beams of old houses in the Southern French Alps.

Sustainable building is not a modern innovation. Even our ancestors recycled not only stones, but also wooden beams of former dwellings, for new huts and furniture. This can be scientifically proven, because the special thing about wood is that its age can be determined with its annual growth rings. And not only that. Among other things, the growth rings can also provide information about climatic and ecological events over the centuries. Dendrochronology is the name of the corresponding scientific discipline, which is also called tree-ring dating. Lisa Shindo is an expert in this field, and wants to track environmental influences in the southern French Alps within the framework of the Cluster of Excellence ROOTS.

The Frenchwoman is captivated by wood, especially old wood. "Wood is a fascinating raw material, vibrant, durable, versatile in its use, and at the same time natural and renewable," explained the 35-year-old. Mankind has always valued wood, because of all these attributes. Not only as a building material for houses, ships, bridges, furniture or instruments, for the production of paper or for heating and cooking, but also – for example as a forest – as natural protection and as a habitat for numerous animals. "It was therefore clear to our ancestors that forests must be cared for, and trees not only felled, but new ones also planted, for example so that erosion would not occur in the mountains," said Shindo, drawing on old forest protection laws. This interaction of humans with trees and the raw material wood is another aspect of her research.

"Humans and trees have always had a special relationship," said Shindo, who has been working at Kiel University for about a year and a half. She is in the process of setting up a dendrochronology department and offering the first seminars. Parallel to this, her research is ongoing. It has led her to the south-east of France to the region around Avignon, where she studies wooden beams in old houses and churches in mountain villages. "The first step in my research is to determine the age of wood used in construction and to analyse the annual growth rings, to see how good the summer was, how much water the tree got. This is shown by the thickness of the growth rings." These measurements are intended to provide data on which she can base further research.

wood samples
© Jennifer Ruske

The annual rings on the wood samples are used to determine the age of the wood - and the period in which the trees grew.

In order to get access to the annual growth rings, the scientist uses a tool to take very thin samples of around 20 centimetres in length, from the outside of the wooden beams right to the core. Photos must suffice for precious items of furniture and instruments. The rings are counted manually with a microscope and special software to support the researcher in her work. Shindo uses the annual growth rings to create a progression curve on the computer, with upward and downward spikes. “If the curve rises, it's a thick ring, so a good year, and if the curve falls, it's a bad year for the tree," explained the dendrochronologist. Using this curve together with historical (climate) data, she tries to date her samples. Already dated reference curves from the region are helpful for this purpose. If her sample and the reference curve have a similar progression, it is certain that both pieces of wood come from the same period. "This makes it possible, for example, to prove whether a historical piece of furniture or an old wooden instrument is an original or a fake," she explained.

As soon as the dating of her extensive sample collection is completed, further research projects are planned. One of these is to reconstruct the climatic conditions of the past in the region, and to derive any special environmental influences. "Everything can be found in the tree rings, the challenge is to decipher it correctly." This is not so simple, because a number of often unknown parameters play a decisive role. The quality of the wood and the type of wood growth – fast or slow – are among them. However, other factors also have an influence on tree growth. If nearby trees are cut down, more light will fall on the tree, which will grow better as a result. In contrast, if individual branches are cut off, this weakens the tree. "Less wood is then produced in this year," explained the expert. "We can therefore often only make hypotheses regarding climate and ecology." To prove these as accurately as possible, in order to get "a complete picture of the region in an era", the scientist collaborates with experts on history, archaeology and geography, geomorphology and other specialist areas, through the Cluster of Excellence ROOTS. But first of all, it's time for her to get back to data collection, a lengthy task. Shindo is fully aware that "counting tree rings will be part of my whole scientific life." However, the exciting look into the past which this enables is absolutely worth the meticulous preparatory work.

Author: Jennifer Ruske