8
Dendrochronology
Frédéric Guibal and Joël Guiot
Dendrochronology differs from other absolute dating methods in that the age assignment is not based on a simple,
automatic count of annual deposits i.e. the rings, but on a set
of intercomparisons of a large number of chronologies so as
to ensure the annual status of each tree-ring (also known as
growth rings), after eliminating the potential pitfall of
anomalies in the anatomy of rings which may result, some
years, in the absence of a ring or the formation of double
rings (also known as false rings).
To understand the principle of this method, some fundamental aspects related to the formation of growth rings in
trees in temperate regions should be recalled. Because of the
marked climatic seasonal contrast of temperate regions an
annual status can be assigned to each ring (with the exception of some accidents in growth).
A Bit of Botany and Ecology
The annual growth of woody plants is composed of an axial
component which leads to the lengthening of branches
(primary growth) and a radial component which leads to the
formation of a ring (secondary growth). The radial growth of
the trunk, branches and roots results from a layer of
actively-dividing cells, the cambium, immediately beneath
the bark. This gives rise to vascular tissues: wood, on the
inside, responsible for, among other functions, the upward
flow of the sap, and phloem, on the outside, responsible for
the downward movement of the elaborated sap (Fig. 8.1).
Year after year, the previously formed tissue is pushed
inwards for wood and outwards for phloem.
In areas with a temperate climate, fluctuations in the
physical aspects of the atmosphere (temperature, humidity,
sunshine) mean that vegetation has a period of activity and a
period of rest within the same calendar year. Cambial activity
is discontinuous in time: in deciduous oaks on the plains in
western France, cambial activity lasts from April to September; for larches which grow in the internal Alps above 1500 m,
cambial activity extends from mid-June to mid-August.
A ring is made up of two parts: the earlywood which
develops at the beginning of the growing season, and the
final latewood which develops later in the growing season.
These differ in terms of the cells that compose them, their
dimensions, their disposition and the thickness of their walls.
Variations in the thickness of the cell walls have consequences for the density of the wood, in the form of
intra-annual and inter-annual variations more or less linked
to changes in climate conditions. These conditions act
according to the principle of limiting factors. Growth cannot
proceed faster than is allowed by the most limiting factor.
This limiting effect may be continuous, variable or sporadic
depending on the case. The action of climatic factors is
attenuated or amplified by other factors, both abiotic (soil,
topography) and biotic (age, competition, pest attacks,
phenology).
Crossdating
Aristotle, Buffon and Leonardo mentioned the existence of
annual tree rings. Leonardo da Vinci, in particular, observed
a relationship between ring widths and the weather conditions of the year. However, it is the American astronomer
Andrew E. Douglass (1867–1962) who, in laying out the
methodological foundations, is considered the father of
F. Guibal (&)
Institut Méditerranéen de Biodiversité et d’Ecologie marine et
continentale, UMR7 263 CNRS/Aix-Marseille Université/
IRD/Univ Avignon, Europôle de l’Arbois, BP 80, 13545
Aix-en-Provence Cedex 04, France
e-mail: Frederic.guibal@imbe.fr
J. Guiot
European Centre for Research and Teaching in Environmental
Geosciences CEREGE, Aix-Marseille University, CNRS, IRD,
INRAE, Collège de France, BP 80, 13545 Aix-en-Provence Cedex
04, France
© Springer Nature Switzerland AG 2021
G. Ramstein et al. (eds.), Paleoclimatology, Frontiers in Earth Sciences,
https://doi.org/10.1007/978-3-030-24982-3_8
117
Dendrochronology
Frédéric Guibal and Joël Guiot
Dendrochronology differs from other absolute dating methods in that the age assignment is not based on a simple,
automatic count of annual deposits i.e. the rings, but on a set
of intercomparisons of a large number of chronologies so as
to ensure the annual status of each tree-ring (also known as
growth rings), after eliminating the potential pitfall of
anomalies in the anatomy of rings which may result, some
years, in the absence of a ring or the formation of double
rings (also known as false rings).
To understand the principle of this method, some fundamental aspects related to the formation of growth rings in
trees in temperate regions should be recalled. Because of the
marked climatic seasonal contrast of temperate regions an
annual status can be assigned to each ring (with the exception of some accidents in growth).
A Bit of Botany and Ecology
The annual growth of woody plants is composed of an axial
component which leads to the lengthening of branches
(primary growth) and a radial component which leads to the
formation of a ring (secondary growth). The radial growth of
the trunk, branches and roots results from a layer of
actively-dividing cells, the cambium, immediately beneath
the bark. This gives rise to vascular tissues: wood, on the
inside, responsible for, among other functions, the upward
flow of the sap, and phloem, on the outside, responsible for
the downward movement of the elaborated sap (Fig. 8.1).
Year after year, the previously formed tissue is pushed
inwards for wood and outwards for phloem.
In areas with a temperate climate, fluctuations in the
physical aspects of the atmosphere (temperature, humidity,
sunshine) mean that vegetation has a period of activity and a
period of rest within the same calendar year. Cambial activity
is discontinuous in time: in deciduous oaks on the plains in
western France, cambial activity lasts from April to September; for larches which grow in the internal Alps above 1500 m,
cambial activity extends from mid-June to mid-August.
A ring is made up of two parts: the earlywood which
develops at the beginning of the growing season, and the
final latewood which develops later in the growing season.
These differ in terms of the cells that compose them, their
dimensions, their disposition and the thickness of their walls.
Variations in the thickness of the cell walls have consequences for the density of the wood, in the form of
intra-annual and inter-annual variations more or less linked
to changes in climate conditions. These conditions act
according to the principle of limiting factors. Growth cannot
proceed faster than is allowed by the most limiting factor.
This limiting effect may be continuous, variable or sporadic
depending on the case. The action of climatic factors is
attenuated or amplified by other factors, both abiotic (soil,
topography) and biotic (age, competition, pest attacks,
phenology).
Crossdating
Aristotle, Buffon and Leonardo mentioned the existence of
annual tree rings. Leonardo da Vinci, in particular, observed
a relationship between ring widths and the weather conditions of the year. However, it is the American astronomer
Andrew E. Douglass (1867–1962) who, in laying out the
methodological foundations, is considered the father of
F. Guibal (&)
Institut Méditerranéen de Biodiversité et d’Ecologie marine et
continentale, UMR7 263 CNRS/Aix-Marseille Université/
IRD/Univ Avignon, Europôle de l’Arbois, BP 80, 13545
Aix-en-Provence Cedex 04, France
e-mail: Frederic.guibal@imbe.fr
J. Guiot
European Centre for Research and Teaching in Environmental
Geosciences CEREGE, Aix-Marseille University, CNRS, IRD,
INRAE, Collège de France, BP 80, 13545 Aix-en-Provence Cedex
04, France
© Springer Nature Switzerland AG 2021
G. Ramstein et al. (eds.), Paleoclimatology, Frontiers in Earth Sciences,
https://doi.org/10.1007/978-3-030-24982-3_8
117