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Our Family Tree

Keywords: cambium, springwood, summerwood, annual ring; Lesson Plan Grade Level: ninth through twelfth grade; Total Time Required for Lesson: 2 hours in 2 days (1 hour each day); Setting: shop or laboratory area

Goals of the Lesson

  • The students will investigate the important dates of their families' heritage.
  • The students will plot the time line of their families' history in years from most current to oldest important dates.
  • The students will become aware of the age of wood and the time it takes for a tree to mature as compared to a human being.
  • The students will realize the importance of sustainable forestry and forest management.
  • The students will appreciate wood as the renewable resource that requires time and management to reach its full potential.

Materials Needed

  • log round; one per student & one demo 10 to 14 inches in diameter by 1.5 inches thick (from sawmill, woodlot, or craft store)
  • quick-drying polyethylene or varnish (water based for easy cleanup)
  • palm sander
  • 1.5-inch paint brush
  • time line sheet of family history
  • card of thumb tacks (available at office supply)
  • 3 x 5 card as a legend to be laminated
  • copies of Our Family Tree homework sheet

State Standards Addressed: Renewable & Nonrenewable resources (4.2.10); Humans & Environment (4.8.10) (4.8.7)

Subjects Covered: history, biology, botany

Topics Covered: human history, tree growth

Methods

The instructor should read over entire lesion and become familiar with the topic, goals, and materials needed.

The instructor should secure the materials required in advance of the lesson date and in amounts sufficient so that each student may participate.

Introduction

"Today's lesson is called 'Our Family Tree.' Each year that goes by in our lives is filled with important events. These events become the history of our lives and those of our family. We've all heard of a 'family tree.' A family tree is a list of births and marriages that traces our families' genetic roots. Today, however, we're going to discuss how a tree records its history. Tomorrow after you all bring back your home work assignment, we're going to compare our family's history and the life of a tree.

A tree's trunk, when looked at in cross section, is a series of rings starting at just under the bark in a circular pattern and extending circle after circle to the center of the trunk. The bark is the hard outer layer of protective tissue around the trunk. Just inside this layer of bark is a thin layer of tissue called 'the cambium' layer. This layer is the only actively growing layer of cells in the trunk and continues to expand a tree's trunk girth till the tree stops growing.

Each year the cambium makes two layers of cells that will form the inner layer we call wood. The first layer is formed each spring and is called (springwood) because it is made up of larger cells that occur in the springtime when growth is rapid. Springwood is usually lighter in color and slightly wider in width than the summerwood. Summerwood is a slightly darker and denser ring next to the springwood. It is formed during the summer when the tree is growing at a slower rate. So, each year is represented by a dark and a light ring. When we look at a trunk in cross section we can count these rings and see how old the tree was. We can also look at the rings to see what physical or climatic changes effected the growth of our tree."

Steps

  1. Each student will now be given their log round and asked to study it. They should choose the best display side and count the rings from the outside to the center. Their names should be taped to the bottom side of the round.
  2. Each student will now bring their round to the shop area where they will be shown how to use a palm sander to smooth out the display side and prepare the wood for sealing.
  3. Each student will have their wood as smooth and dust free as possible and then apply several coats of urethane or varnish. The student must allow time for each coat to dry.
  4. The rounds will be allowed to sit over night until dry and we will continue this lesson tomorrow.
  5. Each student will now be given their homework sheet. This must be filled out and returned for tomorrow's lesson to be meaningful.
  6. Day 2. The students will be gathered in the classroom and their homework assignment checked. They should list all their important dates in chronological order as per sheet.
  7. The student will now place a thumb tack at the corresponding year of each event by counting the rings in a straight line from bark to center of the round. The ring just under the bark is considered year one or the current year.
  8. After all the important family dates are located with a tack, the student will make a legend on the 3 x 5 inch or 5 x 7 inch card, indicating what each tack represents. Number the tacks from outside to center in order by writing on the tack head with a fine permanent marker. See example:

    1 (tack)

    Paula Smith's Family Tree Legend- 1. 2002 Paula- Jr. at DCTS 2. 3.

  9. It would be best if all the legend cards were laminated before gluing onto log round on lower center of round.
  10. Once finished work can be graded and the students can discuss their history in relativity to the tree. For example: How old was this tree? What species of tree was it? Was it a fast- or slow-growing tree? What family event was closet to its beginning?

 

Evaluation/Assessment

 

Ask the students what they've learned from this lesson in terms of family history and forest growth. A short quiz could be given on terminology and each log round should be graded neatness and accuracy.

Reference

Hansen R. S. (1996). Trees & Me = Forestry. University Park, Pa.: The Pennsylvania State University.

Author:

Ronald Fite, Dauphin County Technical School, Horticulture Dept., Grades 9-12