Transcript Tree Rings Can Tell You Things

Tree Rings Can Tell
You Things
About Climate Change
What Can Trees
Tell Us ?
Trees Have Secrets to Share
No, Really! Why Tree Rings?
• Trees live much longer than
humans, and in some cases, for
several thousand years.
Tell me More!
• Each year trees add growth rings,
which can indicate what sort of
growing season the tree experienced.
These rings are more than a
temperature indicator, they also tell
the researcher about moisture and
cloudiness as well.
• Comparing tree rings, living and dead,
scientists can see a history of
weather/climate spanning for 10,000 years.
Is there a Name for this kind
of Science?
• Yes. It is called Dendrochronology.
Dendrochronology is the science
dealing with the study of the annual
rings of trees in determining the dates
and chronological order of past events.
How are scientists learning from tree
rings?
• http://wn.com/tree_rings
The Inside Parts of a Tree
From Stump to Tree Cookie
Another Cookie?
What do these parts do?
•
As a tree grows, older xylem cells in the center of the tree become inactive and die,
forming heartwood. Because it is filled with stored sugar, dyes and oils, the heartwood is
usually darker than the sapwood. The main function of the heartwood for support.
•
The xylem, or sapwood, comprises the youngest layers of wood. Its network of thickwalled cells brings water and nutrients up from the roots through tubes inside of the trunk
to the leaves and other parts of the tree. As the tree grows, xylem cells in the central
portion of the tree become inactive and die. These dead xylem cells form the tree’s
heartwood.
•
The cambium is a very thin layer of growing tissue that produces new cells that become
either xylem, phloem or more cambium. Every growing season, a tree’s cambium adds a
new layer of xylem to its trunk, producing a visible growth ring in most trees. The cambium
is what makes the trunk, branches and roots grow larger in diameter.
•
The phloem or inner bark, which is found between the cambium and the outer bark, acts
as a food supply line by carrying sap (sugar and nutrients dissolved in water) from the
leaves to the rest of the tree.
•
The trunk, branches and twigs of the tree are covered with bark. The outer bark, which
originates from phloem cells that have worn out, died and been shed outward, acts as a
suit of armor against the world by protecting the tree from insects, disease, storms and
extreme temperatures. In certain species, the outer bark also protects the tree from fire.
Trees contain some of nature's most accurate evidence
of the past. Their growth layers, appearing as rings in
the cross section of the tree trunk, record evidence of
floods, droughts, insect attacks, lightning strikes,
hurricanes and even earthquakes.
Each year, a tree adds to its girth
(circumference, or thickness), the new
growth being called a tree ring. Tree
growth depends upon local conditions such
as water availability. Because the amount of
water available to the tree varies from
year to year, scientists can use tree-ring
patterns to reconstruct regional patterns
of drought and climatic change.
A tree ring consists of two layers:
A light colored layer grows in the spring (green dot)
A dark colored layer in late summer (white dot)
During wet, cool years, most trees grow more than
during hot, dry years and the rings are wider. Drought
or a severe winter can cause narrower rings. If the
rings are a consistent width throughout the tree, the
climate was the same year after year. By counting the
rings of a tree, we can pretty accurately determine the
age and health of the tree and the growing season of
each year.
Crossdating is the most basic principle of dendrochronology.
Crossdating is a technique that ensures each individual tree
ring is assigned its exact year of formation. This is
accomplished by matching patterns of wide and narrow
rings between cores from the same tree, and between trees
from different locations.
More Crossdating
Are there limitations using tree rings?
• Trees in the temperate zone only record the growing
season, so the winter season, no matter how dramatic,
will not be seen in the ring record.
• Trees in tropical regions grow year round and
therefore show no real obvious annual growth rings.
Therefore climate data from equatorial areas is difficult
to piece out and use.
• Trees do not grow in all places on Earth, therefore we
don’t have a tree ring record of climate change for
each region and ecologic niche globally. (No trees in
polar regions, high in the mountains, in the ocean!!!)
What other limitations are there?
• The growth of tree rings can be impacted by
many issues - not just rainfall amount,
temperature, and cloud cover – but also by
wind, soil properties, disease, or even
pollution.
What Can We Hope For?
• Fortunately, scientists are gaining new insight
in the reading and use of tree rings, are
hopeful that they can inform us to what
extent global warming has occurred in the
past so we can know what to expect in the
future.
More Info on Climate Change
• If you want to learn more on topics related to
climate change, go to the following website:
http://www.priweb.org/globalchange/climatech
ange/studyingcc/scc_01.html