DENDROCHRONOLOGY

What is dendrochronology?

Dendrochronology: ology: the study of chronos: time, or more

specifically events in past time dendros: using trees, or more

specifically the growth rings of trees

What is dendrochronology?

Tree-rings: Each ring is a year of

growth Each year has early

wood (light-colored) & late wood (dark-colored)

What is dendrochronology? How do we get wood samples?

If the tree is living, we take a core

What is dendrochronology? How do we get wood samples?

If the tree is dead, we take a cross-section of the whole tree

What is dendrochronology?

The Life of a Tree 1769 AD - The tree began

from seed 1867 - The tree was 4 inches

in diameter and 26 feet tall when Alaska was purchased from the Russians.

1917 - The tree was nearly 6 inches in diameter and 37 feet tall during WW I.

1959 - The tree was 22 inches in diameter and 77 feet tall when Alaska became the 49th State.

1977 - The tree was 25 inches in diameter and nearly 90 feet tall when it was felled.

Why is it important?

Using tree-rings, we can learn about:

Past fires: The white arrows indicate

distinct fires of the past Each of those fires has been

dendrochronologically dated to the year it burned

This research is being done at U of A in the Tree-ring Lab

Why is it important?

We can also learn about: climatology: past droughts

or cold periods geology: past earthquakes,

volcanic eruptions anthropology: past

construction, habitation, and abandonment of societies

Why is it important?

We can learn about how trees respond to changes in the environment (physiology) Chemical analysis of rings can determine rates of

water loss & photosynthesis through time By measuring width of rings, can estimate growth

rates of trees through time & understand what affects tree-growth

Why is it important?

Many possibilities Such as settling the age

of an historic violin http://

libpub.dispatch.com/cgi-bin/documentv1?DBLIST=cd01&DOCNUM=55928&TERMV=253:4:333:5:21004:4:36400:4

How do we date tree-rings? Do we simply count them?

No! Trees are trickier than that, some

years they don’t grow at all This creates “missing rings” Sometimes we just have part of a

tree, not the whole tree like the violin

This is why we use pattern matching & match sections of growth with other trees

How do we date tree-rings?

Step 1: Making skeleton plots http://www.ltrr.arizona.edu/skeletonplot/plotting.ht

m Step 2: Cross-dating

Match pattern with a master chronology http://www.ltrr.arizona.edu/skeletonplot/

patternmatching.htm