"Build a Tree" Dendrochronology Activity

The interactive diagram below demonstrates a very simple model of tree ring growth.

Select a temperature range (Normal, Cool, or Warm) and a precipitation amount (Normal, Dry, or Wet) for the coming year. Click the "Add Yearly Growth" button. The tree (which you are viewing a cross-section of the trunk of) grows one year's worth, adding a new ring.

Add some rings while varying the temperature and precipitation. Which of these factors has a stronger influence on the growth of the type of tree being modeled here?

Use the "Reset" button to start over.

The "Show Specimen Tree" button displays a section of an "actual" tree specimen. Can you model the annual climate during each year of the specimen tree's life, matching your diagram with the specimen, to determine the climate history "written" in the rings of the specimen tree? (The "answer" is listed below, lower down this page).

Some Limitations of this Tree Ring Model

Real tree rings are much messier than the ones in the model, but the same principles apply. Credit: UCAR

"All models are wrong... some models are useful." - George E.P. Box

• Real tree ring cross-sections are not so nice and perfectly circular (and centered), or even symmetric, like the ones in this model.
• Different types of trees have different responses in their growth rates to temperature and precipitation. Some really like warm conditions, while others are happiest when it is especially wet.
• Other variables (besides temperature and precipitation) influence growth rates of trees.
• Real trees have a central section called the "pith"; our model starts right in with the first annual ring instead.

The annual climate sequence for the "specimen" tree in the interactive model, starting with the tree's first year of its 15-year long life, is:

1. normal & normal (temperature & precipitation)
2. warm & normal
3. normal & normal
4. warm & normal
5. warm & dry
6. warm & dry
7. normal & dry
8. normal & normal
9. warm & normal
10. normal & normal
11. cool & wet
12. normal & normal
13. warm & normal
14. warm & wet
15. warm & wet