Chapter 8: Trees Are Us

Many schools celebrate Arbor Day by planting young trees to replenish our ecosystem. Trees use carbon dioxide that humans and animals exhale to make oxygen. Trees anchor the soil and prevent erosion. They also produce fruit. Wood from trees is used for the construction of everything from pencils to houses.

As you work through the activities, you will learn more about the uses of trees. You will use formulas to analyze data and predict the production of wood and fruit. Then you will decide how to organize and display your results. 

Task 1: Researching

A board foot is a linear measure of lumber equal to a square foot of wood 1 in. thick.

• • What can you make from 10 board feet? 100 board feet? 1000 board feet? How is the size of a house related to the amount of wood used to build it?

  • What different types of wood are needed for cabinets, floors, and roofs? What tools do carpenters use to make these items?

Task 2: Calculating

You can use the expression 0.0655l(1 - p)(d - s)2 to find the number of useable board feet in a log.

• • Estimate the useable board feet in a 35-ft log if its diameter is 20 in. Assume the log loses 10% of its volume from the saw cuts and a total of 2 in. is trimmed off the log.

• The diameter of a log is 25 in. A total of 2 in. will be trimmed off the log. The estimated volume loss due to saw cuts is 10%. How long must the log be to yield 600 board feet of lumber? 

Task 3: Calculating

With aerial photography, you can study a forest of ponderosa

pines without ever walking through it. To find the diameter

in inches of trees in the forest, use the expression:

3.76 + (1.35 x 10-2)hv - (2.45 x 10-6)hv2 + (2.44 x 10-10)hv3. The variable h is the height of the tree in feet, and v is the crown diameter visible in feet (from a photograph). Determine the diameter of a 100-ft tree that has a visible crown diameter of 20 ft.