The American botanist, Douglas, established the first tree-ring chronology in 1929 with a pine chronology for the south-west of America extending back to 701 AD.In most tree species in the British Isles a single tree-ring is produced each year and the tree-ring’s width varies in response to environmental factors, particularly rainfall and temperature.
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.
Typically, a bachelor's degree in any of the above disciplines are enough to study the data that comes out of dendrochronology.
Trees are a ubiquitous form of plant life on planet Earth.
The radius (r) can be determined from the circumference of the trunk (C=2πr), or from special tape measures that give the diameter directly.
Close-up view of the increment borer, showing the slender wood core that is extracted from the trunk.