Moss is Boss: Using Plants to Determine Direction
AbstractHave you ever gone camping, looked up at the stars, and found the Big Dipper? Two stars in the dipper part of this constellation point to Polaris, the north star, which people have used for thousands of years to help them find their way. In this plant biology science fair project, you'll investigate whether plants, like moss, can help you find your way, too.
Kristin Strong, Science Buddies
To determine whether the location of moss growth on trees is a good way to determine cardinal direction.
Can plants talk? No, but they can still tell you things, like whether spring or fall is coming, if there's a drought, if there's enough nitrogen in the soil, or if a plant has an infection. That's a lot of communication for something that doesn't have a mouth! People have used the signs and signals of nature for thousands of years to make calendars and to figure out the best time to plant crops, to migrate, or to hunt. Following nature was a matter of survival.
Paying attention to natural signs has also been critical to people as they travel. Before the development of the compass, sailors and land voyagers used stars and plants to figure out their cardinal direction (north, south, east, or west) and their latitude (distance from the equator) as they moved from place to place. Perhaps the best-known star for ancient travelers in the northern hemisphere of Earth was Polaris, the north star, which can be found using a star constellation called the Big Dipper (also known as the Drinking Gourd to people who were trying to escape slavery by fleeing north). Stars are fine to use by night, but during the day, people needed another method to figure out their direction. The Sun, of course, can give a general sense of east and west, since it rises in the east and sets in the west, but it's helpful to have more information, especially on cloudy days! The plant that people have turned to most to help them find their way are the lowly mosses.
Figure 1. This photo shows an example of a type of moss. (A. Lin, Wikipedia, 2006.)
Jewel-green, soft, and carpet-like, mosses love to grow where there is low light and moisture. You'll often find them along the edges of streams in the woods, or poking up through cracks in city sidewalks. Moisture is very important to mosses since they are very thin plants, so have no waxy coating to protect them from drying out, and need water to reproduce.
So how does moss relate to cardinal direction? Earth is a sphere and spins on a tilted axis. The result of this arrangement is that in the northern hemisphere, the southern side of any fixed object gets more sunlight than the northern side. The opposite is true in the southern hemisphere. As you can see in the drawings below, the southern side of the tree in the northern hemisphere gets more sunlight, whether it's summer or winter (the Sun is just higher in the sky and has more direct, or straight-on, rays in the summer).
Figure 2. These drawings show that the southern side of objects, like trees in the northern hemisphere, get more sunlight than the northern side, whether it's summer or winter.
So, if you have a lone tree in the northern hemisphere (that is not shaded by any other trees), on which side of the tree do you think moss would like to grow? In this science fair project, you're going to find three such trees and photograph their trunks to see if you really can tell the cardinal direction from the growth of moss on trees.
Terms and Concepts
- Cardinal direction
- Why do people pay attention to the signs and signals in nature?
- Before the development of compasses, how did people figure out in which direction they were going?
- Why does moss like to grow in low-light areas with lots of moisture?
- Which side of a tree gets the most Sun exposure in the northern hemisphere? What about in the southern hemisphere?
These sources discuss moss and the location of its growth:
- EarthSky Contributors. (2008). Does moss only grow on the north side of tree trunks?. Retrieved April 10, 2009.
- Indiana University. (2002, December 2). Is it true that moss grows on the north side of a tree? Don and Yael give the answer on this Moment of Science. Retrieved April 10, 2009.
- Wikipedia Contributors. (2009, March 23). Moss. Wikipedia: The Free Encyclopedia. Retrieved April 10, 2009.
For help creating graphs, try this website:
- National Center for Education Statistics (n.d.). Create a Graph. Retrieved March 19, 2009.
This source describes how a compass works:
- Brain, M. (2009). How Compasses Work. Retrieved April 17, 2009.
Materials and Equipment
- Trees (3)
- With easily visible trunks
- With enough moss on their bases to be visible by a picture taken from a few feet away
- Not crowded or shaded by other trees or buildings
- In a similar geographic area (within a mile or so of each other)
- Compass, available from Carolina Biological, item #: 758669
- Sticks, straight (4)
- Tape measure
- Digital camera
- Graph paper
- Colored pencil
- Lab notebook
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Note: Before starting this science fair project, read about how a compass works in the Bibliography, and play with the compass to familiarize yourself with how to use it. The needle of the compass has an arrow head or a white tip. This is the part to focus on during the experiment. You will line up the arrow head or white tip with N (for north) on the background of the compass.
Testing Your Trees
- Find three trees that meet the requirements listed above in the Materials and Equipment section.
- Place the compass on flat ground near the base of the first tree. Slowly turn the compass until the compass arrow head or white tip is pointing in the same direction as the "N" on the compass.
- Place the first stick at the base of the tree so that it is parallel to the compass needle and pointing north from the base of the tree. This will be your north stick. If desired, use another stick to scratch out an "N" in the dirt beside the north stick to help you remember its direction.
Figure 3. This photo shows how to make the north stick parallel with the needle of the compass.
- From where you are standing looking at the tree, take your compass to the right of the tree in approximately the area that you think west will be. Set your compass on flat ground near the base of the tree. Slowly turn the compass until the needle is again pointing in the same direction as the "N" on the compass.
- Place the second stick at the base of the tree so that it is perpendicular (at a 90-degree angle) to the compass needle (pointing in the direction of west on the compass). This will be your west stick. If desired, use another stick to scratch out a "W" in the dirt beside your west stick to help you remember its direction.
Figure 4. This photo shows how to make your west stick perpendicular to the needle of the compass.
- From where you are standing looking at the tree, take your compass to the right of the tree in approximately the area that you think south will be. Set your compass on flat ground near the base of the tree. Slowly turn the compass until the needle is again pointing in the same direction as the "N" on the compass.
- Place the third stick at the base of the tree so that it is parallel to the compass needle and pointing south from the base of the tree. This will be your south stick. If desired, use another stick to scratch out an "S" in the dirt beside the south stick to help you remember its direction.
Figure 5. This photo shows how to make your south stick parallel to the needle on the compass.
- From where you are standing looking at the tree, take your compass to the right of the tree in approximately the area that you think east will be. Set your compass on flat ground near the base of the tree. Slowly turn the compass until the needle is again pointing in the same direction as the N on the compass.
- Place the fourth stick at the base of the tree so that it is perpendicular to the compass needle and pointing east from the base of the tree. This will be your east stick. If desired, use another stick to scratch out an "E" beside the east stick to help you remember its direction.
Figure 6. This photo shows how to make the east stick perpendicular to the compass needle.
- You will now have four sticks pointing out from the base of the tree in each of the four directions, as shown below.
Figure 7. This photo shows a tree with the four directions marked around its base.
Go to each stick and take a photograph of the base of the tree, using the following instructions:
- Kneel down so that your camera is parallel to the ground as you take the photograph (but it doesn't need to be on the ground).
- Use the stick as a guide for each photograph. As you look through the viewfinder, make sure the stick will be in the bottom center of each photo, as shown below.
- Try to stay the same distance away from the tree for each photograph. You can use the measuring tape to help you stay approximately the same distance away.
- You may want to take a couple of photos just in case your first photo doesn't work out.
- Write down in your lab notebook which stick you photographed first, second, third, and fourth, so that when you take the photos home and print them out, you will know in which direction you were looking.
Figure 8. This photo shows two example photographs taken of a tree from different directions.
- Repeat steps 2–11 for two other trees.
Analyzing Your Photos
- Print out your photos onto graph paper.
- If desired, shade in the moss with one colored pencil and shade in the bark with a different colored pencil to make it easier to distinguish the two on the graph paper.
- Count up the approximate number of squares that are covered by moss. For partial squares, estimate how much of the square is covered by moss, for example, if it looks like one-fourth of the square is covered, add 0.25; if it looks like half of the square is covered, add 0.5; if it looks like three-fourths of the square is covered, add 0.75. For each tree, enter your counts in a data table, like the one below:
Tree 1 Square Counts Data Table
|Direction||Number of moss-covered squares||Total number of tree base squares. (Count up all the squares in the tree base, whether they are covered by moss or just bark.)||Percentage of the tree base covered by moss = (Number of moss-covered squares divided by the total number of tree base squares) x 100|
- Count up the total number of tree base squares (any square that falls within the tree base, whether it is covered by moss or just bark), and enter your count in the data table.
- Calculate the percentage of the tree trunk base that is covered by moss for each direction by dividing the number of moss-covered squares by the total number of tree base squares and multiplying by 100.
- Combine your three data tables into one by entering the last column of each table into a new data table, like the one below.
Percentage of the Tree Bases Covered by Moss Data Table
- For each direction, calculate the average percentage of the trees that were covered by moss and enter your calculations in the data table.
- Make a bar chart showing the four directions on the x-axis and the average percentage of the tree bases that were covered by moss on the y-axis. You can make the bar chart by hand or use a website like Create a Graph to make the graph on the computer and print it.
- In which direction did you observe the most moss growth? In which direction did you observe the least? Do you think moss growth is useful as an indicator of cardinal direction?
Ask an Expert
- Try using mushroom growth around trees, instead of moss. Be careful not to touch the mushrooms, as they could be poisonous.
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