Study of tree rings.
Analysis of the annual rings of trees to date past events.
Analysis of the annual rings of trees to date past events. Samples of wood are obtained by means of a narrow metal tube that is driven into a tree to remove a core extending from the bark to the center. Samples taken from timbers at an archeological site can be compared with a master core on file for that region or by taking cores from old, living trees; the year when they were felled can be determined by locating the point where the rings of the two samples correspond and counting back from the present.
Since annual rings are formed by variations in the water-conducting cells produced by the plant during different seasons of the year, they also provide a means of determining past climatic conditions in a given area (the rings are thin in dry years, thick in moist ones). In North America, sequences of tree rings extending back over 8,000 years have been obtained for the SW and N Mexico by using cores from the bristle-cone pine Pinus aristata, which can live for over 4,000 years in that region. Also, the dryness of the area has preserved wood in SW archeological sites; in wet temperate regions the soil acidity usually absorbs wood, so this dating technique cannot be used.
Nauka koja proučava prstenove drveta (godove).