Ring tree dating
A warm British winter or wet summer will generally have a positive effect on growth (dependent on site factors) and give rise to a wider ring in that year.A harsh winter or dry/hot summer generally has a negative effect on a tree's growth causing a narrow tree-ring in that year.The two 300 year tree-ring sequences may be matched over the 150 year sequence of overlap and thus combined to create a 450 year long tree-ring sequence of known date.Overlapping timbers from modern forests, buildings and archaeology has allowed the annual tree-ring record to be extended backwards over the last 10,000 years.The unique sequence of tree-rings resulting from the pattern of weather conditions match up with the yearly records for weather we have for England over approximately the last 300 years.However, the pattern of weather is recorded in the tree-rings from before this time and when trees were growing at the same time they will broadly show the same unique sequence of tree-rings from the climatic conditions they experienced at that time.Critical to the science, trees from the same region tend to develop the same patterns of ring widths for a given period of historical study.
The tree-ring sequence of these two trees (one of known date and the second tree of possibly unknown date) overlap by 150 years.
The inner portion of a growth ring is formed early in the growing season, when growth is comparatively rapid (hence the wood is less dense) and is known as “early wood” (or “spring wood”, or “late-spring wood”); the outer portion is the “late wood” (and has sometimes been termed “summer wood”, often being produced in the summer, though sometimes in the autumn) and is denser.
Many trees in temperate zones make one growth ring each year, with the newest adjacent to the bark.
Dendrochronology is a science of precise dating, by the accurate counting of annual tree growth-rings, which allows dating wooden items to the year.
The pattern of annual tree-rings differs each year, depending upon the growing conditions at the time.
In addition, particular tree species may present “missing rings”, and this influences the selection of trees for study of long time spans.