Trees and other woody plants grow by covering themselves with a new layer of tissue every year. When seen in a horizontal section, such wood layers appear as concentric tree rings, familiar to anyone who has looked at a tree stump. Because tree growth is influenced by the environment, tree rings are then natural archives of past environmental conditions. For instance, trees grow less when climate conditions are less favorable, producing narrower rings. The study of past changes recorded by wood growth is called dendrochronology.

Besides determining tree age, dendrochronological information has been used in four major fields of scientific research:

• reconstruction of climatic factors that control average wood growth from year to year (such as precipitation, temperature, air pressure, drought severity, sunshine)
  Southern yellow pine tree rings, natural archives of past environmental conditions.
• dating of abrupt events that leave permanent scars in the wood (fire, volcanic eruptions...