Spatial Analysis of School Yard Plot
Objective: Analyze the field map of plants and determine percentage of cover. Develop computer manipulation skills. Design data tables and practice math skills.
The prerequisites are a working knowledge of NIH Image, knowing how to Set Scale, Measure, and Density Slice.
This can be done without a computer by simply counting up the squares covered by each plant and making an estimate of the halves and quarters of coverage. It could also be done more quickly without using the computer, but it isn't as much fun. Cut the time down by a day.
In a perfect world this activity would be practice for a real plot in the desert. See A-3 for assessment.
Digitize the plots that you have drawn up for your school yard exercise. Using NIH Image analyze the spatial arrangements and determine the percentages of each of the plants in the plot.
1) Scan the image using the flat bed scanner.
2) Open the image after it has been digitize (scanned).
3) Choose the Options/Grayscale.
4) Use the measure tool ‡ and measure the length of the plot. Go to Analyze/Set Scale and put down the units and the number meters long of your plot.
5) Go to Options/LUT Options and change Reserved Entries to 6.
6) Select the brush ‰ and choose the green Reserved Entries color with the Ï. Double click on the brush and set the point value to 3.
7) Find a plant on your plot and outline it. Make sure that there are no gaps in your outline. Go and fill in the outline using the paint can Á. (The tip of the dripping paint is the active pixel.) Do this for all the same species of alien.
8) Now go to Options/Density Slice and choose the cursor to move the red density slice on the LUT to a single line by grabbing the top of the red and dragging it clear down to the bottom. With the single line, drag it up to the green color on the top of the LUT. This is kind of tricky so be patient. As a guide, the Info window will tell you which color you are on. If you look down and see that the green is the second the color and the Info window says upper "2" and lower "2" then you are on the green.
9) Now, use the magic wand Î and choose one of the plant outlines. It should start the "marching ants" that indicates it has been chosen. Hold down the shift key ø and you will see a little plus sign on the magic wand. Now find another plant of the same color and click on it. This too should have the "marching ants" around it along with your first one.
10) Choose all of the same color and then choose Analyze/Measure (Hold down the ü and hit 1)
11) Then go to Analyze/Show Results (Hold down the ü and hit 2).
12) Write down the area of the which ever it is. Label this or I will make fun of you if you don't.
13) Now you will have to go back and do the same set of instructions for your each of your plants and then do the Bermuda Grass. You will have a "Show Results" window filled with measurements, each of which means something only to you.
14) Find the total area. If your plot was 3 meters by 1 meter then it is 3 X 1 = 3 square meters.
% of Bermuda grass = [Area of Bermuda grass *100] / Total Area of Plot
15) Draw up a chart showing the percentages of Bermuda grass versus all of the alien invaders. Then if you're really good, use Claris Works to make a pie chart showing the percentages of cover of each known plant.