Wind Dynamics and Forests

In this activity, students will set up a model forest using plastic bottles to observe changes caused by differences in wind speed and differences in forest density. An extension to the activity will allow students to explore the concept of evapotranspiration.

Background

While we often think of climate as a non-biological factor that influences ecosystems, changes in the structure and distribution of living organisms in an ecosystem can, in fact, have profound climate effects both regionally and globally.

Changes in vegetation affect regional atmospheric phenomena, including rainfall and evapotranspiration as well as convection and winds. It is well documented that vegetative changes due to human activity have led to significant climatic consequences. For example, desertification increases the albedo (reflectivity) of the land surface, further reducing local rainfall.

Changes in vegetation reflect and influence the interaction of the land surface and the atmosphere. In this exercise, students explore this powerful but often unexpected interaction by using a simple model of a forest under different wind conditions.

In this activity, students will set up a model forest to observe changes caused by differences in wind speed and differences in forest density. An extension to the activity will allow students to explore the concept of evapotranspiration.

Learning Goals

  1. Students will understand that living organisms in an ecosystem can have profound effects upon the local atmosphere.

  2. Students will understand that changes in vegetation can have profound effects upon wind speed.

  3. Students will understand that models are useful to researchers in understanding the shaping of ecosystems.

Alignment to National Standards

National Science Education Standards

Benchmarks for Science Literacy, Project 2061, AAAS

Grade Level/Time


Materials

Main Activity

Extension activity

Procedure

Main activity

  1. Pour about 2 inches of sand into each soda bottle.

  2. Arrange the bottles on a table in eight staggered rows, three bottles in each row with each row approximately 12 inches apart. The bottles represent the "forest."



  3. At one end of the table, place a fan on a stool level with the table.

  4. Place a wind meter level with the table at the opposite end from the fan.

  5. Turn the fan to low and record the wind reading. Record the wind reading at tabletop (ground level), at approximately six inches above the table (mid-canopy level), at the top of the bottles (top of the canopy), and slightly above the bottles (above the canopy).

  6. Turn the fan to a higher level and record.

  7. Remove eight bottles, simulating a selectively cut timber operation.

  8. Repeat steps 5 and 6.

  9. Randomly remove eight more bottles and repeat steps 5 and 6.

  10. Remove the remaining eight bottles and again repeat steps 5 and 6.

To make the 'forest' more realistic, you may use different sized bottles to represent different ages or species, although the activity works just as well representing a 'monoculture' forest.

Observations and Questions

  1. Make a table of the results for wind speeds at various levels in the forest when the forest was dense and undisturbed.

  2. Make other tables for each stage of cutting, for example, one third of the trees removed, two-thirds of the trees removed, and all the trees removed.

  3. Graph the results. You might have the students divide into groups with each group graphing a different portion of the data.

  4. Have students compare their graphs and then discuss the significance of the experiment. What does the experiment show?

  5. What might be done to improve the model used?

  6. What other environmental parameters might also show changes as a forest is cut?

Extension

Evapotranspiration from a vegetation canopy is also strongly influenced by wind pattern and direction. Following the wind speed activity, you may wish to simulate a moist forest canopy by:

This would perhaps best be done as a 'quick and dirty' qualitative analysis of drying levels (which paper towels are completely dry, which remain wet, which are partially dry).

Following the activity, discuss with the students the implications of greater or lesser

Assessment Ideas

Ask students to imagine a rainforest with frequent rainfall, abundant water, and a low wind speed within the canopy (where most of the plants and animals live). Either by timber harvest or disease, trees begin to disappear. Create three labeled graphs to illustrate how the environment within the original forest might change with the loss of trees.

In a paragraph, explain the significant changes illustrated by each graph.

Modifications for Alternative Learners

When you're finished with the activity, click on Back to Activities List at the top of the page to return to the activity menu.