Bristlecone pine carbon dating
While American scientists were building bristlecone pine and Douglas fir chronologies, European scientists were actively building a very long tree-ring chronology using oak trees.
Tree-ring chronologies have been extended to 10,000 years before present in this way.
The more ancient part of the chronology was constructed from oak logs preserved in peat beds, for example.
The European oak chronology provided an excellent check of the American dendrochronologies. Ring-width patterns are determined by local environmental factors, such as temperature and rainfall.
Separate dendrochronologies were then developed, also in America, using other types of trees, such as Douglas fir.
These separate chronologies did not extend as far back in time because these types of trees are shorter-lived.
Generally, it is not possible to construct a complete sequence of tree rings back through the historical periods using only living trees.