Study of Tree Rings Information
Dendrochronology is the science of studying and dating tree rings. It can be used to determine the age of a particular tree. When several trees in a specific area are studied, the tree rings can give clues to geological or environmental occurrences in that area.
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Counting Rings
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By counting the number of rings on a tree trunk you can tell the age of the tree. Each year a new layer of wood, or a ring, is added to the growing tree. The rings have both a light growth section and a narrower, dark section. Scientists can use a method called coring to take a small, but long, crosswise section out of the trunk in order to count the rings and not harm the tree.
Ring Width
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In years where the growth conditions are favorable, the tree will add rings that are wide. If the tree has gone through a period of drought or cold or was stressed in any way, it will add narrow rings to its trunk. Disease, insect damage, and competition for nutrients from other trees or plants can also cause narrow rings.
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Cross Dating
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Dendrochronolgists use cross dating to make the study of the rings more accurate. By sampling and comparing the tree ring data from many specimens within an environmentally similar area, scientists can identify the exact year of a ring's formation.
Skeleton Plotting
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One method of cross dating is called skeleton plotting. Scientists note the variations of tree ring width on strips of graph paper. Each graph represents an individual tree. Scientists then compare the graphs, looking for similar patterns.
Conifer Ring Formation
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The rings of conifers, or evergreens, are different than those of angiosperms, those trees that have leaves that turn brown and fall off in the winter. In conifers, the earlywood, or light section, has cells that are large in diameter but with thin walls. The latewood, or dark section, has smaller cells but the cell walls are much thicker.
Angiosperm Ring Formation
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Angiosperms have vessel cells that are part of the tree's vascular system. These cells do not appear in conifers. In the earlywood, these vessel cells are larger in diameter than in the latewood.
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References
- Photo Credit Image by Flickr.com, courtesy of Rene Ehrhardt
