Observing Tree Rings

Observing Tree Rings

by Liz LaRosa

www.middleschoolscience.com

Objectives:

to determine the age of a tree
to see if we can determine what years had more precipitation than others
to label the cross section of a tree: bark, heartwood, sapwood, rings
to practice collecting class data, stem and leaf and data tables
to reinforce lab notebook procedures

Procedure:

Make a rubbing of half of your tree section in Figure 1. Label the bark, heartwood, sapwood, and rings
Count the rings of your tree; a light and dark band represents one year. Record in Table 1.
Look at your rings, look for dry years and wet years. Record in Table 1.
Measure the diameter of your tree in cm. Record in Table 1. Place on the Stem and Leaf on the board and in Figure 2.

Data:

Figure 1: Rubbing of tree cross section. Label the bark, heartwood, sapwood, and rings (whole page)
Table 1: Tree Ring Data (1/2 page)

# of Rings
Diameter of Tree cross section	cm
# of dry years
# of wet years

Figure 2: Stem and Leaf of Tree Diameter (1/2 page)
Table 2: Summary Data Table (1/2 page)

n=		mean=
max=		med=
min=		Q3=
range=		Q1=
sum=		IQR=

Analysis:

How many rings do you have? How old is your tree?
Why aren't rings made in the winter?
What is the function of xylem? phloem?
Were there any years of little rainfall? heavy rainfall? How can you tell?
According to your tree, were there more dry seasons than wet seasons?
What is the diameter of your tree?
MATH QUESTIONS !!! What is the area of your tree cross section? What is the circumference of your tree? Show work! Formulas to use: ( A = pr²) ;( C = 2pr ); use p=3.14

Conclusion: 2-3 complete sentences on what you learned today.

TEACHER NOTES:

Background Information: Trees grow annually producing rings as they grow. A light layer is produced in the spring when growth is the fastest, a darker ring in the summer where slower growth occurs. You can determine the age of a tree by counting the rings. Tree rings can also give clues to the amount of rainfall in a growing season. Narrow rings indicate slow growth, wider rings indicate rapid growth. Wood is made mostly of xylem cells: these are used to conduct water. Heartwood is found in the center of the tree and is made of xylem cells that do not carry water anymore. Sapwood surrounds the heartwood and is made of xylem cells that still carry water. The outermost layer is made of phloem cells (these conduct sugars made by the leaves) and cork, together they make up the bark.