Estimate the effects of aboveground traffic on soil properties and communities.
Impacts of Schoolyard Traffic
Students will know that the presence of humans has an impact on soil communities in their schoolyard.
- For the "super soil" OBIS component; see list in OBIS handout.
- For the percolation test, each group of students will need a soup can with both ends removed, a water source, and a container to measure water with.
- For the survey of soil animals, each group should have a magnifier, a data sheet, and a clipboard.
- Soil temperature may also be measured; each group of students will need a thermometer.
- Each group should select 2 areas on the schoolyard to be compared with respect to physical features associated with schoolyard traffic. Select one area with heavy kid traffic and one area with little or no kid traffic, but try to keep the general habitat the same. For example, a path through a section of woods edge and an area just off the trail would be ideal. OR, use an area of a grassy playground that is heavily trodden (e.g. soccer field goals!) vs. spots in the same area with little traffic (perhaps just behind the goal). Have the children PREDICT which location will have more soil organisms and/or a greater variety (diversity) of living things than the other and WHY this may be the case. Most children will probably predict that the disturbed areas will have less - make sure they back up their reasons for WHY because the point of this exercise will be to discover some of the physical features associated with "disturbance/traffic" that may impact the living communities. Conduct each of the following measurements (or any subset the teacher selects) at BOTH sites.
- "Super Soil," an OBIS activity (http://www.outdoorbiology.com/node/91). Have the children describe (in writing) the characteristics of the soil at the 2 sites - color, texture, odor, graininess, lumpiness, etc. Secondly, conduct an ALUM test at each site to determine the amount of ORGANIC material present in the soil. Which site has a higher organic content? Make sure the children record their results. A quantitative way to report the results would be to measure the depth of the organic layer in the tube by measuring it with a cm ruler.
- Percolation. Percolation here will be used as an indication of how compacted the soil is and how much water runoff might be expected in the two areas. Insert the soup can about 2 cm into the ground at the site to be measured by twisting. Try not to disturb the soil on the inside of the can. Pour 50 ml of water into the can and time how long it take for all of the water to percolate into the soil. Record this time. For areas that have a LONG percolation time (water sits in the can), we would associate slow percolation of water into the soil and high surface runoff during rain, watering, etc. What is the significance of high surface runoff? EROSION!
- Temperature. Measure the temperature just beneath the surface of the soil at each site by inserting the bottom red bulb of the thermometer into the soil until the entire bulb is just covered.
- Ground Creatures. You may elect to have the children to census only animals or only plants or both. In either case, select a plot size that will be consistent from group to group. Stretched coat hangers or large embroidery hoops, or circles of string about 20 cm in diameter are all possibilities. Have the children count and record each variety of organism and the number of each on their data sheet. Remember that the number of different kinds (= biodiversity) is every bit as important as how many creatures.
- Do this exercise in combination with the Decomposers on Jello exercise beginning on page 196 of Eco-Inquiry by Kathleen Hogan. Have the children predict before-hand where there will be fewer vs. greater microbes that decompose dead plant and animal bodies. Also see the extensions listed in this exercise for growing funguses in baggies - again - the two areas could be contrasted for decomposer activity in this way.
- See the follow-through extensions listed in the Super Soil Obis handout.
- If you have a hill on your schoolyard, measure the amount of erosion that occurs when water runs down a trampled part of the hill vs. a vegetated/grassy part of the hill. All you need is a mound such as the one at Van Raalte Elementary! See OBIS: "Hold-a-Hill."
Hogan, Kathleen. 1994. Eco-Inquiry: A Guide to Ecological Learning Experiences for the Upper Elementary/Middle Grades. Kendall/Hunt Publishing Co. Dubuque, Iowa.
"Super Soil." Outdoor Biology Instructional Strategies. Published by Delta Education, 5 Hudson Park Drive, Hudson, New Hampshire, 03051.
Hope College, 1994