Terrestrial
Ecosystems

5th grade spring unit

revised February 21, 2008

What is an ecosystem?

An ecosystem is a self-sustaining, self-regulating community of plants and animals interacting with one another and the physical environment upon which they are dependent. Non-living parts of the ecosystem include sunlight, air, water, and the land.

How are ecosystems dependent on the physical environment?

Every living organism has needs and preferences when it comes to their surroundings. Some animals are very specific, others can live almost anywhere (or have sub-species that can). As the physical surroundings change, so do the plants and animals that live there. It can work the other way, too, as plants and animals can have impacts on their surroundings that effect the ability of other plants and animals to live there.

What are some examples of how biological (living) parts of an ecosystem change from year to year?

From bare land arise plants that prefer open space and plenty of sunlight. As those plants mature, other plant species move in as well, eventually shading out the early plants before themselves losing out to other species. Meanwhile, every stage of plant growth also has certain species of animals associated with it. For example, white-tail deer thrive in areas of early succession with plenty of short shrubs, bushes, and grasses, but don't fare as well in the deep, tall forests with little undergrowth that come later. On the other hand, raccoons do better in old, mature woods but not so well in a young forest with few old, dead trees in which to live.

Here is a good web page that tells more about forest succession in Minnesota.

What are some examples of how the landscape in an ecosystem changes from year to year?

The forces of wind, rain, moving water, gravity, sunlight, temperature, plant growth, and animal activity are always changing the physical landscape around us. Two primary categories of these changes are erosion and weathering.

Erosion - Erosion is simply the removal of ground materials (soil, sand, rocks) by water or wind. While most people are already familiar with this term, it's often easy to forget about deposition. Everything that is washed away has to be deposited somewhere else. These are the most obvious natural forces and they are still changing our landscape today.

Weathering refers to different forces that are changing rocks in a very short time, even day to day. If you throw a rock down on the sidewalk and the rock breaks, that's a type of weathering called physical weathering. Physical weathering happens whenever some force breaks a rock into smaller pieces by forcing them apart. Another type of weathering, called chemical weathering occurs when something "eats away" at a rock rather than breaking it apart, such as water dissolving a rock or sunlight changing the color of a rock.

What will we do at River Bend?

You and your team will visit River Bend's Big Woods forest and complete a series of tests and observations -- sort of a "snapshot" assessment of that part of the terrestrial ecosystem. Eventually you will compare your results to those of other teams and in future years teams will make comparisons to yours.

You and your team will:

• Record date and the weather conditions at the time of your visit.
• At your study plot in the Big Woods forest (Forest worksheet):
  • Use the densiometer you made back in the classroom to measure the forest leaf canopy cover (download plans).
  • Measure the diameter of the largest tree(s) in your plot using a special tape measure.
  • Use a prism tool to measure the forest density in your study plot.
  • Measure the pH of the soil in your plot using a special kit and the temperature of the soil with a dial thermometer.
  • Note any wildlife signs you encounter.
• At a series of study points along the "Great Bend" of the Straight River (see actual aerial photo of section of river you will study!) (River worksheet):
  • Use a tape measure to determine the height and width of the a small stream that feeds into the river, as well as it's exposed bank.
  • Measure the width of the river with a range-finding tool
  • Judge the turbidity (clear or dirty) of the water flowing that day
  • Map the Great Bend valley, noting features of erosion, deposition, and weathering.
• Your data will be compiled with data gathered by other teams on this web page to generate ranges and averages for future comparisons.

What are some basic principles of a scientific investigation?

Science is often a process of performing scientific tests to investigate and learn things. For example, we can test a sample of water to see how much oxygen is present in a pond. In order for such tests to have any meaning, there are some rules (or "principles") that we must remember:

• Follow all directions and safety instructions for a test carefully.
• Do each test the same way each time you do it.
• When measuring something, be as exact as possible.
• Doing the same test several times and taking an average can give you a better answer to question than doing just one test.

What do we need to remember when we visit River Bend?

1. The quieter we are, the better.
2. Listen to your leader.
3. Be careful and safe with all tools and equipment
4. Raise your hand if you have something to say.
5. Do not pick anything unless given permission.
6. Stay where you leader asks you to be.
7. Be respectful of nature - and of each other!

2007 data reports

Some suggested pre- or post-visit activities

Send us your ideas here!

• Create model of a river valley ecosystem out of some media, and another predicting how it will look 20 years from now.
• Monitor the results from other classes posted on this site to include in graphing. (In the future, most value will be gained by comparing results from different years).
• Research other types of terrestrial ecosystems, in North America and around the globe.
• Monitor and research current news stories on land changes, such as mud slides, sink holes, bank erosion, etc.

Interesting links

The following links contain some interesting information on changing terrestrial ecosystems: Send us your ideas (and broken links) here!

Here is a page that talks about mud slides

This one discusses serious beach/bank erosion

(c) River Bend Nature Center
Faribault MN USA
www.rbnc.org
rbncinfo@rbnc.org
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