Dendrochronology

The growth rings of a tree at Bristol Zoo, England. Each ring represents one year; the outside rings, near the bark, are the youngest

Dendrochronology (or tree-ring dating) is the scientific method of dating tree rings (also called growth rings) to the exact year they were formed in a tree. As well as dating them, this can give data for dendroclimatology, the study of climate and atmospheric conditions during different periods in history from the wood of old trees. Dendrochronology derives from the Ancient Greek dendron (δένδρον), meaning "tree", khronos (χρόνος), meaning "time", and -logia (-λογία), "the study of".^[1]

Dendrochronology is useful for determining the precise age of samples, especially those that are too recent for radiocarbon dating, which always produces a range rather than an exact date. However, for a precise date of the death of the tree a full sample to the edge is needed, which most trimmed timber will not provide. It also gives data on the timing of events and rates of change in the environment (most prominently climate) and also in wood found in archaeology or works of art and architecture, such as old panel paintings. It is also used as a check in radiocarbon dating to calibrate radiocarbon ages.^[2]

New growth in trees occurs in a layer of cells near the bark. A tree's growth rate changes in a predictable pattern throughout the year in response to seasonal climate changes, resulting in visible growth rings. Each ring marks a complete cycle of seasons, or one year, in the tree's life.^[2] As of 2020, securely dated tree-ring data for the Northern Hemisphere are available going back 13,910 years.^[3] A new method is based on measuring variations in oxygen isotopes in each ring, and this 'isotope dendrochronology' can yield results on samples which are not suitable for traditional dendrochronology due to too few or too similar rings.^[4]

^ The term "dendrochronology" was coined in 1928 by the American astronomer Andrew Ellicott Douglass (1867–1962). Douglass, A.E. (1928). Climatic Cycles and Tree Growth. Vol. II. A Study of the Annual Rings of Trees in relation to Climate and Solar Activity. Washington, D.C., USA: Carnegie Institute of Washington. p. 5. From p. 5: "One can see that in all this we are measuring the lapse of time by means of a slow-geared clock within trees. For this study the name "dendro-chronology" has been suggested, or "tree-time." "
^ ^a ^b Grissino-Mayer, Henri D. (n.d.), The Science of Tree Rings: Principles of Dendrochronology, Department of Geography, The University of Tennessee, archived from the original on November 4, 2016, retrieved October 23, 2016
^ Van der Plecht, J; Bronck Ramsey, C; Heaton, T. J.; Scott, E. M.; Talamo, S (August 2020). "Recent Developments in Calibration for Archaeological and Environmental Samples". Radiocarbon. 62 (4): 1095–1117. Bibcode:2020Radcb..62.1095V. doi:10.1017/RDC.2020.22. hdl:11585/770537.
^ Loader, Neil J.; Mccarroll, Danny; Miles, Daniel; Young, Giles H. F.; Davies, Darren; Ramsey, Christopher Bronk (August 2019). "Tree ring dating using oxygen isotopes: a master chronology for central England" (PDF). Journal of Quaternary Science. 34 (6): 475–490. Bibcode:2019JQS....34..475L. doi:10.1002/jqs.3115.

[1] The term "dendrochronology" was coined in 1928 by the American astronomer Andrew Ellicott Douglass (1867–1962). Douglass, A.E. (1928). Climatic Cycles and Tree Growth. Vol. II. A Study of the Annual Rings of Trees in relation to Climate and Solar Activity. Washington, D.C., USA: Carnegie Institute of Washington. p. 5. From p. 5: "One can see that in all this we are measuring the lapse of time by means of a slow-geared clock within trees. For this study the name "dendro-chronology" has been suggested, or "tree-time." "

[Grissino-2] Grissino-Mayer, Henri D. (n.d.), The Science of Tree Rings: Principles of Dendrochronology, Department of Geography, The University of Tennessee, archived from the original on November 4, 2016, retrieved October 23, 2016

[3] Van der Plecht, J; Bronck Ramsey, C; Heaton, T. J.; Scott, E. M.; Talamo, S (August 2020). "Recent Developments in Calibration for Archaeological and Environmental Samples". Radiocarbon. 62 (4): 1095–1117. Bibcode:2020Radcb..62.1095V. doi:10.1017/RDC.2020.22. hdl:11585/770537.

[4] Loader, Neil J.; Mccarroll, Danny; Miles, Daniel; Young, Giles H. F.; Davies, Darren; Ramsey, Christopher Bronk (August 2019). "Tree ring dating using oxygen isotopes: a master chronology for central England" (PDF). Journal of Quaternary Science. 34 (6): 475–490. Bibcode:2019JQS....34..475L. doi:10.1002/jqs.3115.

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