by Linda Finnegan

Created on: July 18, 2011   Last Updated: July 19, 2011

Simply put, dendrochronology is the study and dating of the annual growth rings in a tree. The word comes from three word parts: “ology” meaning the “study of”; “chronos” referring to time; and “dendros” which refers to trees. This sophisticated science is more than just counting and measuring tree ring width, however. The analysis, cross dating, and cataloging of tree rings in a certain geographical region aids a variety of related sciences including archeology, ecology, paleocology, and radio carbon dating.

History

Dendrochronology was first developed by astronomer A.E. Douglas, who began his work in 1894 with a study of old beams from buildings, sequoias and other long-living trees. He discovered a link between tree ring growth and sunspot cycles. He worked to understand the interrelationships around sunspot activity, climate patterns and tree ring growth. Working with the American Museum of Natural History and the National Geographic Society, Douglas began to compile tree chronologies for several tree species and regions. In 1937, he was the first scientist to teach dendrochronology at the University of Arizona and founded the Laboratory of Tree-ring Research there.

Tree Ring Science

Tree rings are obtained by cutting a horizontal cross section through the trunk of a tree. One ring of growth is produced by the tree annually. This year-by-year record reflects climate conditions of that year. Trees growing in the same region will develop similar ring patterns. They also reflect historical traumas to the trees such as fire damage, pollutions, and infestations. Chronologies are developed by matching patterns of ring growth from one tree to another and assigning dates to the rings. Dead wood and live wood are both used in the chronologies. The bristlecone pine tree of the American Southwest has a developed chronology of 8,500 years. In Europe, the European Oak and Pine chronology is 11,000 years long. Studies are continuing in South America, China, Russia, and Spain. Modern cross-dating is made easier with the use of computers. The International Tree-Ring Data Base is a permanent repository for tree ring data from around the world.

Applications

Dendrochronology helps to calibrate other sciences. For example, wooden beams from ancient buildings can be compared to known chronologies and be dated. Historians were able to observe that few buildings were built during the Black Death during the 14th Century and during other plagues. Art historians have been able to date panel paintings by Rubens and Rembrandt because they painted on wood imported from Gdansk in the Eastern Baltic. Dendrochronology also helps to back up the radio carbon dating process.

Ecologists and paleocologists work to determine past climates from tree rings. Scientists can determine climate conditions such as temperature, sunlight, precipitation, and wind from tree rings. They also can determine some aspects of the soil and even when there were pest outbreaks. This helps them determine past climate changes and whether global warming is being repeated or is something very new. It puts climate change in a historical context and helps scientists plan for the future. Dendrochronology is also an important tool in the study of volcanic activity, hurricane activity, glacial movement, mass movement, precipitation, and much more.

Sources

http://en.wikipedia.org/wiki/Dendrochronology

http://ltrr.arizona.edu/about/treerings

http://ltrr.arizona.edu/

http://en.wikipedia.org/wiki/A._E._Douglass

http://www.arts.cornell.edu/dendro/ajatext.html

http://sonic.net/bristlecone/dendro.html

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