The document discusses the principle of cross-dating tree rings. [1] Cross-dating involves matching patterns in tree ring widths or characteristics among multiple trees to identify the exact year each ring was formed. [2] This allows scientists to synchronize the tree ring chronologies and date wood samples far into the past without relying solely on ring counting. [3] Cross-dating is essential for dendrochronology because of various complications that can occur with tree ring formation.
15. Weather and climate act to synchronize growth rates
at the level of the cell, the tree, the forest and beyond.
16. “ RINGS ”
IN THE BRANCHES OF
SAWED TREES SHOW
THE NUMBER OF YEARS
AND, ACCORDING TO THEIR
THICKNESS,
THE YEARS WHICH WERE
MORE OR LESS
DRY.
Leonardo da Vinci
23. THE PRINCIPLE OF CROSS-DATING
Matching pa erns in tree-ring widths or other ring characteristics
(such as ring density) among several trees allow the identification
of the exact year in which each ring was formed.
46. PLE
-RING SAM
EE
HE TR
N WH ERE T
OSITI O LLEC TED!
AT THE P WA S CO
A “missing ring” is a term used to describe the
phenomenon where a tree does not form wood
around its trunk during a single growing season.
57. Bur oak (Quercus macrocarpa) is a common tree along rivers in Minnesota and the upper Midwest.
Select trees of this species can live for up to 450 years.
63. What kind of trees have rings that can be dated?
• They have distinct and detectable rings.
• Their rings must be reliably annual.
• The formation of their rings must be
sensitive to environmental conditions.
• That sensitivity must cause the rings to vary
from year to year.
• Several trees must share common pa erns
in tree-ring width, wood density or some
other wood variable.
67. ‘Complacent’ tree-ring series:
• exhibit very li le year-to-year variation.
• grow in se ings where the limiting growth
factor doesn’t change much.
• are tough to cross-date.
72. ‘Complacent’ tree-ring series:
• exhibit very li le year-to-year variation.
• grow in se ings where the limiting growth
factor doesn’t change much.
• are tough to cross-date.
‘Sensitive’ tree-ring series:
• have wide and narrow rings that are
intermixed through time.
• Found in environments where the limiting
factor is highly variable year to year
• Matching ring pa erns across trees is
easier.
73. September 20
The principle of cross-dating
Source: Baillie (1982)