We can date organic archaeological material and create a chronological record against which artefacts can be dated (3).
It is an accurate and reliable dating method with a large number of uses in environmental studies, archaeology and everything in between.
The method has gone from strength to strength and is now a vital method across multiple disciplines.
From the 1980s, several seminal studies began at the University of Arizona (6), (7) studying the bristlecone pine of California and hohenheim oak in Germany.
Thanks to the work of these studies, we now have an 8,600 year chronology for the bristlecone pine and in the region of 12,500 year chronology for the oak.
Some trees are also better than others for study (5). In this article we make the assumption that growth is annual with a distinct growing season.
Most tree species are reliable; oak is the most reliable tree type for tree rings - with not a single known case of a missing annual growth ring.Before this, their ancestors would have a recognisable tree form, believed to be that of a giant type of fern that began the process of developing a woody stem.Wood helps the developing tree to stay strong as it gets older and grows upwards, building new branches and drinking in more sunlight for photosynthesis reproduction.In each growth season, trees create a new ring that reflects the weather conditions of that growth season.On its own, a single record can tell us only a little about the environmental conditions of the time in a specific year of the growth of the tree, and of course the age of the tree at felling, but when we put hundreds and thousands of tree-ring records together, it can tell us a lot more.This says nothing about either when the particular tree was felled, nor about the date it was used (8).