The ages of trees
What the annual rings tell us about trees.
Annual tree rings – autobiography of trees
To unfold its leaves in spring, the tree has to transport an enormous amount of nutrients from its roots up to its crown. To do so, it builds relatively large-diameter transport vessels (xylem and phloem). In summer and autumn, cells are increasingly generated to store reserve substances and to stabilize the trunk. We can see these differences with the naked eye as a color transition from lighter early wood to darker late wood. Tree growth is suspended in winter.
This process is repeated every year. Therefore, we can determine the age of a tree by counting the number of annual tree rings on a slice of the trunk. Annual rings are not equally recognizable in all tree species. The rings of larch, Douglas fir, ash, and oak can be clearly seen. With maple or birch, the contrast between early and late wood is not that great and counting is difficult.
Annual rings tell stories
You can see from the annual rings how the tree has fared in the course of its life. If they are narrow and close together, the living conditions were not so good. This may have been due to drought, lack of nutrients, pests, or a constricted tree top. Wide growth rings indicate a strong growth and that the tree has experienced the best living conditions. Scientific research with annual tree ring widths is called dendrochronology. It makes it possible to determine from an old wooden beam or slice of tree trunk when and how the tree lived.
Early wood: light-colored areas arise from spring (new growth) to summer.
Late wood: denser and thus darker wood is formed from late summer to autumn.
Timeline overview
1794 Justus Möser dies.
Möser promoted sustainable forest management in the ecclesiastical principality of Osnabrück.
1803 Imperial Recess.
The ecclesiastical principality of Osnabrück and its entire forest property became part of the Electorate of Braunschweig-Lüneburg.
1833 Liberation of the Peasants.
Johann Carl Bertram Stüve from Osnabrück, as a member of the Estates Assembly in Hannover, initiated the liberation of the peasants in Germany.
1865 Order for the protection of habitat trees. T
he central forestry office of Prussia ordered all administrating forest officials to “protect hollow, damaged trees here and there to preserve the breeding places of the so important tree hollow brooders”.
1866 The Kingdom of Hannover becomes Prussian.
1904 Birth of the Jewish painter Felix Nussbaum in Osnabrück (died 1944 in Auschwitz).
1910 Zeppelin LZ 7 “Germany” crashes.
The Zeppelin LZ 7 “Germany” crashes during a storm on Limberg near Iburg.
1932 Integration of the district of Iburg into the county of Osnabrück.
1939 Beginning of World War II
1949 Foundation of the Federal Republic of Germany.
The Basic Law comes into force.
1954 The “Miracle of Bern.”
Germany becomes soccer world champion for the first time.
1969 The first people land on the moon.
1972 Formation of the county of Osnabrück in its current form.
1990 German reunification.
1991 LÖWE Decree.
Program in Lower Saxony for long-term ecological forest development.
2002 Designation of the nature reserve “Freeden,” including the natural forest “Großer Freeden”
The annual rings in tree trunks are created by the changing seasons. In spring the tree builds large-diameter transport vessels, as it needs to transport lots of water and nutrients to the tree top to unfold its leaves. The wood that is formed during this time is light-colored. In summer and autumn, cells are created that store nutrients and strengthen the trunk. This wood is darker colored. A tree ring consists of a layer of light spring wood and a layer of darker late wood.
Wood grain
If you cut long boards from a tree trunk, the annual rings form lines and patterns in the wood. This is called the grain. Using these patterns, an expert can recognize which tree species the wood comes from.
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