Dendrochronology
Dendrochronology is the science of
dating tree rings.
It includes investigations of the
information content in the structure
of dated rings and applications to
environmental
and
historical
questions
(Kaennel
&
Schweingruber, 1995, Multilingual
glossary of dendrochronology).
The trees (in our climate zone) every
year produce a tree ring (also
called growth ring, annual ring or
growth layer).
Terminal
ring
(waney
edge,
German “Waldkante”) is the last ring
below the bark.
Example of a tree, with the terminal
ring formed in 2001.
Wood for investigations can be
obtained from trees or constructions
by coring.
The cores are processed so that
their microscopic structure can be
clearly
seen
under
a
stereo
microscope.
Measurement. In most cases we
measure tree ring widths.
Measuring equipment generally
consists of a stereo-microscope and
a measuring table connected to a
personal computer with programme
for data acquisition and processing.
Tree-ring
series
a
graph
representing tree-ring widths vs.
time.
Undated tree-ring series. Relative
year does not represent a calendar
year of a ring formation.
The trees of the same species from
the same site generally show similar
tree-ring patterns. We can crossdate or synchronize them.
When we want to date wood of
unknown origin we can cross-date it
with a reference chronology.
A chronology of an object (green
curve) cross-dated with a reference
chronology (red line). Date end is
1953.
Long reference chronologies are
usually composed of chronologies of
trees prolonged with chronologies of
historical objects.
Example: local chronology of silver
fir (Abies alba) from Pohorje, NE
Slovenia (details in graduation thesis
Stopajnik 1997 and article Levanic &
Cufar
Zbornik
gozdarstva
in
lesarstva, 1998).
Teleconnection
represents
synchronisation of chronologies from
distant sites. The European fir has a
good teleconnection.
The chronologies from Pohorje (NE
Slovenia) have similar tree-ring
patterns as chronologies from a
Dinaric region (SW Slovenia). The
two regions belong to different
phytogeographical
regions
with
different climate, soil, vegetation
type etc.
Chronologies are constructed for
different wood species, geographical
regions and periods.
Local chronologies are composed
from site chronologies within a
locality.
Regional
chronologies
are
composed
of
several
local
chronologies and are generally
representative for a wood species
from a larger region.
Picture - origin of wood from trees
and historic buildings to compose a
regional
larch
(Larix
decidua)
chronology
representative
for
Slovenia and NE Italy.
Time spans of chronologies of trees
and buildings and a resulting 1242
years long regional chronology
of larch for Slovenia and NE
Italy. (Details in Levanic, Pignatelli,
Cufar Dendrochronologia, 2001).