16
Vegetation-Atmosphere Interface:
Tree Rings
Joël Guiot and Valérie Daux
A Dendrochonological Approach
In many parts of the world, there is a strong seasonality in
the annual distribution of temperatures and rainfall. This
seasonality is reflected in the growth of trees, which is the
result of the interaction of the tree with its environment, via
its leaves (for carbon and water exchanges) and its roots (for
nutrients and water). In temperate latitudes, during the
winter, the tree is dormant and woody cells are not produced.
In spring, when the thermal conditions are met, the tree
becomes active and starts to produce large, dispersed woody
cells (early wood). Towards late spring and early summer,
the cells produced are denser and smaller (late wood), then,
at the end of the summer, cells are no longer produced along
the trunk and the tree starts to store reserves for the following year. If a trunk is cut through, alternating light and
dark bands can be observed, which, combined, constitute an
annual growth ring. Comparison between rings shows a high
level of variability. This variability is the direct consequence
of the climate conditions (temperature, rainfall, sunlight)
which prevailed during or before the formation of the cells
(Fritts 1976).
These seasonal growths are produced by tissues in the
cambium, a layer of cells between the wood and the bark
which causes expansion in the diameter of the roots, trunk
and branches of the tree. Besides climate, the thickness of
the ring also depends on many other parameters including
the species, the age of the ring, the availability of nutrients in
the soil, the tree’s ability to retain water, its exposure etc.
Douglas (1920) was the first to recognize the potential of
series of annual growth rings to provide information about
past climates, and he established the fundamentals of what is
now known as dendroclimatology. The main difficulty is to
distinguish the impact of climate from other factors. The
greater the climate stress the tree is subjected to, the easier
this is to decode. Generally, there are two types of climate
stress: heat stress and water stress. In arid or semi-arid
regions, tree growth is limited by the availability of water.
Therefore, this will be the main parameter recorded by the
tree. Trees in the far north or at high altitudes are constrained
by temperature. This makes them very good thermometers.
The climate conditions in the months prior to the growing
season also affect the ring. These may be the replenishment
of groundwater reserves, or carbon reserves ready to be
activated for the following year. This further complicates the
decoding of climate information.
The dendroclimatic approach (Cook and Kairiukstis
1990; Trouet 2020) involves taking a number of cores from a
given forest, at a rate of between two and four cores per tree
from ten to twenty trees per stand. A core is a small tube
taken from the bark to the middle of the tree, from which the
sequence of rings can be read. The trees most likely to
provide the best information on the climate parameter to be
reconstructed are chosen. For example, when reconstructing
a water parameter, trees growing in shallow soils which are
unable to store much water will be selected. Each core is
then dated by counting the rings from the bark to the heart of
the tree. Each ring is supposed to be annual, but sometimes
growth stops during the season because of a temporary
drought and resumes if it starts to rain. This resulting growth
arrest produces what is called a false ring. For this year, there
are two rings. In other years, conditions are so unfavorable
that the ring appears to be missing. These two types of
phenomena will produce errors in the dating of rings. Cross
dating, that is, the comparison of series between cores, helps
eliminate these errors.
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
e-mail: guiot@cerege.fr
V. Daux
Laboratoire des Sciences du Climat et de l’Environnement,
LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, 91190
Gif-sur-Yvette, 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_16
197
Vegetation-Atmosphere Interface:
Tree Rings
Joël Guiot and Valérie Daux
A Dendrochonological Approach
In many parts of the world, there is a strong seasonality in
the annual distribution of temperatures and rainfall. This
seasonality is reflected in the growth of trees, which is the
result of the interaction of the tree with its environment, via
its leaves (for carbon and water exchanges) and its roots (for
nutrients and water). In temperate latitudes, during the
winter, the tree is dormant and woody cells are not produced.
In spring, when the thermal conditions are met, the tree
becomes active and starts to produce large, dispersed woody
cells (early wood). Towards late spring and early summer,
the cells produced are denser and smaller (late wood), then,
at the end of the summer, cells are no longer produced along
the trunk and the tree starts to store reserves for the following year. If a trunk is cut through, alternating light and
dark bands can be observed, which, combined, constitute an
annual growth ring. Comparison between rings shows a high
level of variability. This variability is the direct consequence
of the climate conditions (temperature, rainfall, sunlight)
which prevailed during or before the formation of the cells
(Fritts 1976).
These seasonal growths are produced by tissues in the
cambium, a layer of cells between the wood and the bark
which causes expansion in the diameter of the roots, trunk
and branches of the tree. Besides climate, the thickness of
the ring also depends on many other parameters including
the species, the age of the ring, the availability of nutrients in
the soil, the tree’s ability to retain water, its exposure etc.
Douglas (1920) was the first to recognize the potential of
series of annual growth rings to provide information about
past climates, and he established the fundamentals of what is
now known as dendroclimatology. The main difficulty is to
distinguish the impact of climate from other factors. The
greater the climate stress the tree is subjected to, the easier
this is to decode. Generally, there are two types of climate
stress: heat stress and water stress. In arid or semi-arid
regions, tree growth is limited by the availability of water.
Therefore, this will be the main parameter recorded by the
tree. Trees in the far north or at high altitudes are constrained
by temperature. This makes them very good thermometers.
The climate conditions in the months prior to the growing
season also affect the ring. These may be the replenishment
of groundwater reserves, or carbon reserves ready to be
activated for the following year. This further complicates the
decoding of climate information.
The dendroclimatic approach (Cook and Kairiukstis
1990; Trouet 2020) involves taking a number of cores from a
given forest, at a rate of between two and four cores per tree
from ten to twenty trees per stand. A core is a small tube
taken from the bark to the middle of the tree, from which the
sequence of rings can be read. The trees most likely to
provide the best information on the climate parameter to be
reconstructed are chosen. For example, when reconstructing
a water parameter, trees growing in shallow soils which are
unable to store much water will be selected. Each core is
then dated by counting the rings from the bark to the heart of
the tree. Each ring is supposed to be annual, but sometimes
growth stops during the season because of a temporary
drought and resumes if it starts to rain. This resulting growth
arrest produces what is called a false ring. For this year, there
are two rings. In other years, conditions are so unfavorable
that the ring appears to be missing. These two types of
phenomena will produce errors in the dating of rings. Cross
dating, that is, the comparison of series between cores, helps
eliminate these errors.
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
e-mail: guiot@cerege.fr
V. Daux
Laboratoire des Sciences du Climat et de l’Environnement,
LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, 91190
Gif-sur-Yvette, 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_16
197