TREE GROWTH IN ADJACENT MICROCLIMATES

David Garvin

OVERVIEW: In this lesson, students use a map to predict variations in microclimates. Working in pairs, they take basic environmental information and produce diagrams of "tree cookies" showing the growth rings that would be produced in a young tree. This lesson is designed to follow a lab activity where students examine and interpret tree cookies. The objective of this lesson is to reinforce those concepts while illustrating the existence of microclimates in close proximity.

GEOGRAPHIC QUESTIONS:

1. How do different microclimates in a small area impact the growth of trees?

2. In what ways do annual variations in precipitation and other local conditions impact tree growth?

3. How would climate factors affect the placement of a new tree in your yard?

CONNECTION WITH CURRICULUM: Lesson fits into current Life Science curriculum regarding plants and ecology.

NATIONAL GEOGRAPHY STANDARDS: The physical processes that shape the patterns of Earth's surface. (#16)

OREGON GEOGRAPHY CONTENT STANDARD EIGHT GRADE BENCHMARK: Use maps to analyze spatial distributions and patterns.

OREGON SCIENCE CONTENT STANDARD EIGHTH GRADE BENCHMARK: Describe how animal and plant structures adapt to environmental change.

GRADE LEVELS: Planned for 6th-9th. With modifications this activity could be done at any level.

OBJECTIVES: Students will:

1. Map the tree locations.

2. Analyze the microclimates of the four locations.

3. Use environmental information provided to predict the growth of young trees.

MATERIALS: Map of Area (attached), List of Events (attached), two or three tree cookies, metric ruler, paper, and pencil. Optional item: compass.

PRESENTATION STEPS:

1. Review by having students list things that green plants need to get from their environment to grow (water, carbon dioxide, light, and nutrients.)

2. Have students measure the ring spacings on a couple of cookies to get an idea what the ring spacing for good and poor growing years might be. Create a table on the board for the students to refer to. For example:

Poor year------1 mm

Average year--2 mm

Good year-----3 mm

Great year-----4 mm

3. On overhead show attached area map.

4. Explain that the students will be receiving a paper stating the locations of some young trees and a year by year listing of important environmental factors.

5. Handout "Lists of Events" and Maps.

6. Ask students to plot the location of the four tree seedlings on the map.

7. Tell students to use the information provided in the List of Events and the table on the board to predict the growth rings that would be created each year on the four seedlings.

8. After discussion of results, ask students to sketch a map of their yard and identify the “best” location for a new tree to grow. Have the students write a few sentences justifying their decision.

ASSESSMENT: Student's tree cookies will be graded on the reasonableness of their data interpretation.

Excellent/A-Shows understanding of the impact on tree growth of sunlight, rainfall, and nutrients levels.

Good/B-Shows understanding of the impact on tree growth of sunlight and rainfall levels.

Fair/C-Shows understanding of the impact on tree growth of sunlight levels.

Poor/D-Has about the right number of rings on each of the four cookies.

ADAPTATIONS: If they are working alone, students with learning difficulties can be assigned fewer trees to do. They may also require reading assistance.

EXTENSION: Imagine you are a forester looking at this area in 2010. Which tree (or trees) would you remove to enhance the growth and health of the remaining trees? Explain why you choose the tree (or trees) that you did.

LIST OF EVENTS

1990 Four Douglas Fir seeds sprout in the area shown on the map.

A--at the X.

B--5 m West of the X.

C--5 m North of the X.

D--5 m Southeast of the X.

The soil throughout the site has moderate amounts of nutrients, except under the alder where the phosphorus levels are low. The ground slopes down to the south at about 10 degrees. The alder is 2 m tall. Rainfall is average.

1991 Rainfall is average.

1992 Deer eat about half the leaves from the blackberry. Rainfall is above average.

1993 The alder is now 3 m tall. Rainfall is above average.

1994 An owl often uses the alder tree as a roost. It scatters owl pellets and droppings around under it. Rainfall is average.

1995 The owl continues roosting in the alder. A large branch of the alder is broken off by a windstorm. Rainfall is average.

1996 The owl moves to a new hunting area. Rainfall is below average.

1997 Tree C is now taller than the blackberry. The alder is 4 m tall. Rainfall is below average.

1998 Rainfall is below average.

1999 A bear looking for beetle grubs rolls the rock down the hill. The rock tears the bark of tree B. Rainfall is average.

2000 A very cold hard winter causes deer to eat lower buds on all of the trees. The alder is 5 m tall. Rainfall is very heavy.

2001 Caterpillars attack the alder tree, eating about half of its leaves. Rainfall is above average.

2002 Rainfall is average.

2003 A cougar kills a deer and buries the uneaten part of the carcass just north of tree A. The carcass rots away during the year. Rainfall is average.

2004 Rainfall is below average.

2005 A family of ground squirrels dig a burrow at the base of tree B. The alder is 6 m tall. Rainfall is above average.

2006 The squirrels expand their den by digging more tunnels near tree B. Birds build nests in trees A and C. Rainfall is average.

2007 The trees' outer limbs begin to touch one another. Rainfall is above average.

2008 A bear digs up a large portion of the squirrel burrow under tree B. The surviving squirrels move elsewhere. Birds are now nesting in all of the trees. Rainfall is below average.

2009 The trees' outer limbs are now in close contact with each other. Rainfall is average.

2010 Another large limb is broken off the alder tree by a windstorm. It falls on tree D breaking several of its limbs. Rainfall is average.