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.

Sue-etics Bobography Is there a Name for this kind of Science? Fredology 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?

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 thick- walled 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: ange/studyingcc/scc_01.html