uni'wissen 02-2015_ENG

“Traces left by tools and the cross section of woods provide information about the woodworking process. Growth rings and anatomical features are used for dating and paleoecological analyses,” summarizes Tegel. What he produces in the end can be seen on a computer screen. Maps of Europe shaded in green and brown flash in rapid succession over the screen: one map for each of the past 2500 years. Each of them shows precisely where in Europe there was too much rain, where it was dry, where it was warm, and where it was cold. The year 1315, for example, was unusually rainy, while at the beginning of the 15th century there was a drought of dramatic proportions that lasted more than 20 years. The catastrophic conse- quences for humans are documented by written records, but the trees provide much more precise information on the weather conditions. From the Late Glacial to the Present Tegel’s research material is scattered all over his laboratory: pieces of wood from various epochs and in various formats. There are thick discs from Black Forest pine trunks and drill core samples of ancient oak wood, thin as a cotton swab and fit into narrow rails to protect them from damage. These sam- ples were taken from beams and posts built into houses, fences, and well shafts hundreds or even thousands of years ago. Tegel works with wood from epochs ranging from the Late Glacial – the last period of the last ice age or circa 12,500 to 10,000 before Christ – to the present. His research material comes The photograph shows a stately polar bear strolling along an Arctic beach in front of the deep-blue Arctic Ocean. Dr. Willy Tegel has this picture in mind when he sits at his computer at the University of Freiburg’s Institute of Forest Sciences. The archaeologist encountered the polar bear in Greenland in the summer of 2010, and this meeting was so unpleasant that he immediately evacuated the small camp he shared with other scientists and ran for shelter. And the bear wasn’t even what he was inter- ested in: what Tegel was after was the gray trunk of driftwood visible in the foreground of the snap- shot. The wood that washes ashore on the Arctic coasts is “a unique archive of the climate and environment,” says the scientist. In a long-term research pro- ject, he determined the origin and age of trunks, great numbers of which are washed onto the beach- es of the virtually treeless islands of the North Atlantic. So much wood from Siberia and North America reaches the shores of Greenland and Iceland that the sawmills don’t work with any other wood. Precise Dating Tegel began specializing in tree-ring dating as a student. The scientific name for this young discipline, dendrochronology, is derived from “dendron,” the Ancient Greek word for tree. Dendrochronology is a method for determining the precise age of wood and is used among other things to date valuable historical musical instruments. By analyzing archaeological finds made of wood, dendrochronologists can also reconstruct the climactic conditions of the time in which they were made. uni wissen 02 2015 “The growth rings of trees are as precise and individual as a barcode.” 17 rain, where it was dry, where it was warm, and where it was cold. The year 1315, for example, was unusually rainy, while at the beginning of the 15th century there was a drought of dramatic proportions that lasted more than 20 years. The catastrophic conse- quences for humans are documented by written records, but the trees provide much more precise information on the weather conditions. From the Late Glacial to the Present And the bear wasn’t even what he was inter- ested in: what Tegel was after was the gray trunk of driftwood visible in the foreground of the snap- shot. The wood that washes ashore on the Arctic coasts is “a unique archive of the climate and environment,” says the scientist. In a long-term research pro- ject, he determined the origin and age of trunks, great numbers of which are washed onto the beach- es of the virtually treeless islands of the North Atlantic. So much wood from Siberia and North America reaches the shores Growth ring research, also known as dendrochronology, is a method for determining the precise age of wood. uni wissen 022015

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