Objectives: Students will understand
how the scientific method can be applied in their own backyard
and how shade and sunlight is important for various plants.
Related Web-Activity: Forest
Rebirth
Subjects: Ecology, Biology, Agriculture
ELRS: Mathematics 1.1, 1.2, 5.2;
Science 1.3, 2.1, 3.1
Size: Classroom, groups or individuals
Setting: Backyard or school yard.
Duration: Fifteen minutes, three
times per week for two months
Materials: Radish seeds or another
species of quick-growing vegetable and a wide sheet of paper
Background
Scientists at North Cascades use the scientific method for solving
problems created by past land management practices, as in the case
of fire suppression in the Stehekin Valley. Historically, summer
drought conditions in the Stehekin Valley have led to periodic lightning-caused
forest fires in this rainshadowed region. This natural fire regime
supports ponderosa pine, whose seedlings depend on open forests
and meadows that are created by periodic burning.
Although some tree species depend on open-forest conditions, others,
such as Western hemlock, are shade tolerant and are able to slowly
mature in low light conditions. These species dominate areas with
wetter conditions on the west side of the Cascades. Although they
are dominant on the west side of the park, Western hemlock rarely
dominate in fire-dependent forests; these 'shady characters' are
usually snuffed out by fire.
Apply the scientific method by testing the light tolerance of a
common vegetable species under various shade conditions in your
backyard.
Procedure
Teachers, discuss the scientific method with your students and
demonstrate how the method is essentially problem solving. We have
outlined the scientific method into seven steps as it applies to
North Cascades Fuel Reduction Plan.
Follow each step of the scientific method during your experiment:
1) State the Problem
How much shade or sunlight do radishes or other garden vegetable
require for best growth?
2) Gather background information
What does the gardening literature say about the amount of light
needed by radishes? Assign this task to two classroom researchers.
3) Create an hypothesis
Discuss with your students possible outcomes and have them predict
where the best light conditions will be if plants are left out
in the yard.
4) Test the Hypothesis
Distribute ten plants around the yard in varying degrees of shade.
You can also do this project indoors on a windowsill and create
artificial shade factors. Then make a 12 column chart on a wide
sheet of paper: a) plant name, b) location, c) shade factor, d)
- j) seven columns for plant height, k) average circumference
of radish bulb, and l) comments.
Fill columns a) through c) for each plant. You will need to
assign a shade factor of 1 - 10 by making an educated guess of
the varying degrees of shade available for each plant.
5) Make and Record Your Observations
Have two students water plants daily (you may need to let them
go unwatered over the weekend) and take notes if anything out
of the ordinary happens to the plants. Each plant should receive
the same amount of water. Have two students record plant height
each week on the same day.
6) Analyze the Data
After seven weeks of growth have been recorded, harvest the
radishes, remove the tops and measure average bulb circumference
by measuring a vertical and horizontal circumference and averaging
the two measurements for each bulb. Graph average circumference
of surviving radish plants and compare to the estimated shade
factor.
7) Make Conclusions
Which shade condition is best suited for radishes? Where did
the experiment go wrong and how would you remedy the difficulties
next time?
Extensions
Survey your yard for shade-tolerant plant species. Log all the
species you find in a designated survey plot. Be sure that the area
contains both shady and full sun areas. If you don't know the species
name, devise your own. When you list each clump of a species, note
its location and define an estimated shade factor from one to ten
for the location. After all the clumps of plants have been recorded,
plot each species on a graph. Each column will represent a different
species. For each column, plot each occurrence of the species marking
its recorded shade tolerance factor. (You will need to estimate
for the shade tolerance factor: the most shaded areas will receive
a 10, while the sunniest areas will receive a 1.) The end result
will demonstrate the shade tolerance range for each species. Notice
that some species are found in a broad range of light conditions,
while others are only found in specific light conditions.
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