Dendrochronology dating definition
See the cal BP discussion for additional information about radiocarbon calibration.Tree-ring dating works because a tree grows larger--not just height but gains girth--in measurable rings each year in its lifetime.Not all trees can be measured or used without additional analytical techniques: not all trees have cambiums that are created annually.In tropical regions, for example, annual growth rings are not systematically formed, or growth rings are not tied to years, or there are no rings at all.A recent attempt to use tree ring analysis on olive trees (Cherubini and colleagues) revealed that too much variation of the cambium occurs in olives to make dendrochronology viable.The rings are the cambium layer, a ring of cells that lie between the wood and bark and from which new bark and wood cells originate; each year a new cambium is created leaving the previous one in place.
Because of that precision, dendrochronology is used to calibrate radiocarbon dating, by giving science a measure of the atmospheric conditions which are known to cause radiocarbon dates to vary.Radiocarbon dates which have been corrected--or rather, calibrated--by comparison to dendrochronological records are designated by abbreviations such as cal BP, or calibrated years before the present.Dendrochronology is the formal term for tree-ring dating, the science that uses the growth rings of trees as a detailed record of climatic change in a region, as well as a way to approximate the date of construction for wooden objects of many types.As archaeological dating techniques go, dendrochronology is extremely precise: if the growth rings in a wooden object are preserved and can be tied into an existing chronology, researchers can determine the precise calendar year--and often season--the tree was cut down to make it.
Evergreen cambiums are commonly irregular and not formed annually.
Trees in arctic, sub-arctic and alpine regions respond differently depending on how old the tree is--older trees have reduced water efficiency which results in a reduced response to temperature changes.