It's All in the Rings

Concepts to Be Covered

• Impact of nature and man on tree growth
• Trees are resilient: they respond to adversity in order to survive

Goals for the Lesson

• Students will become aware of how trees grow.
• Student will analyze growth rings to see how plants adjust to adverse conditions in order to survive.
• Students will learn more about the anatomy of a tree.

Teaching Model: Focus, Explore, Reflect

Academic Standards Addressed: 4.3.7; 4.5.10; 4.7.7; 4.7.10

Introduction

This lesson is designed to explore the growth of trees. Although trees do not have nervous systems and therefore lack nervous responses, they certainly do respond to changes in their environment. We will look inside a tree and try to arrive at some conclusions about changes in growth patterns in it's life history.

Focus Phase (15 minutes) Pass out handouts and use overhead transparencies of tree cross sections to identify the internal anatomy of a tree. Discuss the value and importance of each part with the class. Analyze the life history of a hypothetical tree. (See data sheet, tree layers, and tree rings.)

Explore Phase (20 minutes)

Preparation

Prior to class, have your woodshop teacher saw a small log (preferably a hardwood at least 20 to 25 years old) into 1-inch sections. Sand or plane the surface so that it is smooth and the growth rings are clearly visible.

Procedure

1. Students should work in pairs. The only materials they need are a ruler, a section of the tree, and a data sheet to record their observations.
2. Count the rings and determine the age of the tree.
3. Measure the diameter of the each ring in millimeters (be sure to take measurements in several places along the growth ring, then average them for accuracy). Record the answers on the data sheet.
4. Using the largest as excellent and the smallest as poor, rate the tree's growth for each year of its life. Rate the growth as excellent, good, fair, or poor. Record the choices on the data sheet.
5. Each team should record their results on the board or overhead transparency.

Reflect/Conclusion Phase (15 minutes)

Once all the data is recorded, provide students with the following information:

• Species of tree
• Where the tree was growing
• Weather data for the years the tree lived (use Internet sources)
• Other possible factors such as plant diseases, insect infestations, natural disasters, and human-made situations that could have made an impact on the tree's growth.

Have each student write a report that indicates what they feel caused variations in the tree as it grew each year. There is no absolutely correct answer, but students should be able to see that plants do respond to changes in their environment, both natural and human made.

References

Hansen, Robert S., and James C. Finley (1996). Trees + Me = Forestry . University Park, Pa.: The Pennsylvania State University.

Ketchum, Richard M. The Secret Life of the Forest. American Heritage Press. 1970.

Author

William Lundvall, Indian Valley High School