Cross dating for dendrochronology
This item is part of the Tree-Ring Research (formerly Tree-Ring Bulletin) archive.
It was digitized from a physical copy provided by the Laboratory of Tree-Ring Research at The University of Arizona.
There is clearly a difference between the calcium content of wood during the wet and dry seasons that compares favorably with carbon isotope measurements.
The calcium record can be determined in one afternoon at the synchrotron lab compared with four months in an isotope lab.
In this example, wood Sample D dates back to the year 1691.
This represents an unbroken succession of 291 annual rings, almost three centuries of time recorded in four small pieces of wood.
The ultimate decision whether or not a tree-ring series is successfully crossdated must lie with the dendrochronologist and not with the software.
Therefore, the program is most useful after initial crossdating is accomplished using visual or graphical techniques (such as skeleton plots), and the rings have been measured.
australis) on a steep 9,000 foot ridge of Pine Mountain in the San Gabriel Range of southern California.
The 1906 ring pattern in wood Sample A (which was cut from Stump A) correlates with a 1906 ring pattern in Sample B which was cut from an older, undated Stump B. By matching up similar spaced rings in Samples B, C and D, the ages of ancient timbers can be determined.
As long as the wood samples being compared have some ring patterns that coincide, time may be extended back through an unbroken succession of growth rings.
Often the borer does not reach the center of the trunk, so the total number of years must be extrapolated from the radius of the trunk.
The radius (r) can be determined from the circumference of the trunk (C=2πr), or from special tape measures that give the diameter directly.