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# Tree Ring Model

#### Summary

While working in groups to facilitate peer tutoring, students manipulate a hands-on, physical model to better comprehend the natural variations of tree-ring width and their uses for determining past climatic conditions. Students use the model as a real-world data sample, collect direct observations from the specimen, and infer past climate conditions.

## Learning Goals

Students will understand:
• How to obtain the age of a tree by counting its rings.
• Learn that differences in tree ring width can be used as a proxy precipitation indicator.
• Be able to interpret the general climatic pattern of a region using tree ring data.

## Context for Use

This model works best during units on global climate change and can be used to demonstrate one method that climatologists use to determine past climates. Ideally students each have their own specimens, however one board can be used with up to four students at a time. Regardless of the number of students per board, working within a group allows students to instruct their peers on how to interpret the data.

## Teaching Materials

Each student model consists of one board cut such that the center of the tree is visible (a 1 x 12 pine board cut width-wise into pieces approximately 8 cm wide works well).

## Teaching Notes and Tips

Students determine the age of their specimen by counting the number of rings visible on the end of the board starting from the center. To foster inquiry, do not explain how trees produce rings or why they indicate. Some groups will count each light and dark band as separate rings. Some groups will count all of the rings from one side of the board to the other without identifying the center.

After students have counted the rings on their specimen, address how trees produce rings and how to properly age the specimen. Also have students discuss factors that might affect ring width. Have student reexamine their block of wood and identify places where the rings are close together and places where they are farther apart. Discuss these patterns and what conclusions can be drawn about the climatic variations experienced by that tree.

Caution:
• Some students will count each light and dark band as a separate ring
• Students may count all of the rings that are visible across the board rather than the rings from the center outward
• The actual age will be a minimum because the entire tree width is not exposed. There will be a distribution of ages depending on the direction in which the board was cut

## Assessment

Several different assessment techniques can be used depending on time and the needs of your class.
• If you have a personal response system, you can ask ConcepTest questions that focus on the use of tree rings to determine past climates. (See References and Resources for sample ConcepTest questions)
• By walking around the class, the instructor can observe how well the groups comprehend the underlying concepts and ask individual students to explain their conceptual understanding
• Students could complete a worksheet containing questions about the use of tree rings to construct past climates.
• Students could write a 'minute paper' explaining how tree ring variability is used to determine past climates.

## References and Resources

Archived tree-ring activities:

Biology:Ecology

## Resource Type

Activities:Classroom Activity:Short Activity:Demonstration, Activities