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The Age of Redwood Trees
First postedMay 3, 2004 Last updated June 30, 2004
Redwoods are some of the oldest plants
on the planet. The tallest are our coastal redwoods,
and the most massive are the giant redwoods. More information
on the oldest, tallest, and largest, is here.
Bristlecone
pine trees are the oldest, dating back 4,767
years. They are very slow growing pines, with
some very old specimens found at Wheeler Peak,
in the White Mountains of the southern Sierra
Nevada. This tree is named Methuselah. It is
mostly comprised of dead wood, with only a little
living cambium and foliage. The climate conditions
are very harsh, permitting only very slow growth.
These same conditions, however, prevent rotting
away of the dead wood and the preservation of
the tree.
Giant redwoods can live to be 3000 years old.
How do we know how old they are? Tree rings
and dendrochronology! What's all this? Read
on! |
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Trees do not grow at the same
rate all year long. In the spring, the conditions
for growth are better than they are during the
winter. Therefore the cells laid down during
the spring (called "early wood") are
larger than the cells laid down during the winter
(called "late wood"). This results
in the formation of one light band and one dark
band, which are merely alternating layers of
larger cells that appear lighter in color, and
layers of smaller cells that appear darker in
color. Together these bands represent one year
of growth. Counting the rings tells how old
the tree is.
Redwood trees have been found in one
study of old growth to have between 25 to
50 rings per inch of wood. A tree that is 8
feet wide could be 2400 years old. Second growth
usually is faster, and the rings are not as
close together. |
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The science of studying growth
rings is called dendrochronology. It can yield
insights into past climate conditions, forest
conditions, dating of old wooden structures, and
similar conditions.
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| We have a cross section of a redwood
tree at Cazadero (seen at right) that is 350 years
old. We have marked it with the birthdates of some
of the important musicians: Mozart, Beethoven, Stravinsky.
If you look at it, you will see that the redwood
grew very quickly while it was young (the first
100 years), adding about 8 inches in girth. It grew
slightly slower the second 100 years, about 6 inches,
and then very slowly the last 150 years:only 2 1/4
inches! We have used this to calculate the age of
our oldest trees, and we believe that they are 2,250
years old. |
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