Soil erosion lab
Samantha Smithers, Amber Mitchell, Maggie McCaffity
Introduction:
Deforestation is everywhere around us, in our communities, in our forests, and in our world. Ever since deforestation has become a prevalent force in our world people have been examining the effects it has on our environment. What many people may not realize are the effects beyond the ones most widely known, such as added carbon dioxide and decreased oxygen in the atmosphere, which are the ones on the ecosystems left behind after the vegetation is cleared. If vegetation and trees are kept in an area, the amount of soil erosion that takes place can be kept to a minimum because there are an abundance of roots deep down in the soil. This keeps a lot of nutrients and moisture in the soil and allows the animals in the ecosystem to prosper. In addition to the amplified effects that can take place without vegetation in an area, these effects also happen much quicker. Buffer zones have been used for many years as another method to reduce soil erosion by setting aside an area designated for environmental protection. Buffers can have a positive impact on agriculture by reducing erosion, improving water quality, increasing biodiversity, and expanding wildlife habitats. Buffers remove sediment from surface runoff and reduce concentrations of nutrients and pesticides. Research demonstrates that buffers can be effective in promoting environmental quality in and beyond agricultural landscapes. In this lab those effects are measured using similar scenarios set up on a smaller scale to see the amounts of soil erosion, water, and the time it took for the water to seep out of the soil.
Problem: How does grass affect the movement of water in an ecosystem?
Hypothesis: If we add 100 mL of water to a different type of soil (grass, ground-cover, and soil), then the soil growing the grass will have the least amount of erosion because the roots will hold the soil in place and absorb the water, while the just soil/ ground-cover will have a larger amount of soil erosion.
Materials:
- 2 liter
bottles, cut in half
- Potting
soil
- Grass seed
- Water
- Pebbles,
gravel or leaf litter
Sowing the seeds
1. Place soil in an empty 2L bottle that has been cut in half (see picture above). Spread grass seed evenly throughout the soil.
2. Water grass seed every 3-4 days and allow it to sit near a source of sunlight or under a plant grow lamp.
Testing the effects
- When the grass has grown 2-4 inches in height, you are ready to test the effects.
- Fill two more empty 2L bottles with soil. Cover one with a top cover of your choice (gravel, pebbles, or leaf litter) and leave the other one alone as a control.
- Place one of the bottles up on top of an elevated surface. Place an empty beaker underneath the mouth the bottle.
- Prepare a graduated cylinder with 100 mL of water.
- Have a student start a timer and say “GO.” When the timer says go, pour the water into the soil/grass.
- Record the time, amount, and color of the water discharge in the table below.
- Repeat for the other two bottles.
Data:
Bottle: Water Collected: Water stopping time: Characteristics
With Grass 50 mL 11.6 sec Clear water
With Ground cover 49 mL 9.8 sec Light shade of brown
With Soil Only 123 mL 19 sec Very dark, murky
Data Analysis:
In the bottle with only soil, the water was very dark and murky. In the bottle with rocks and soil, the water was a lighter shade of brown than the first bottle. In the bottle with grass, the water was much clearer than the other bottles. In class we talked about positive loops of ways to prevent erosion. I found that my hypothesis was very accurate. The test bottle with just grass had the least amount of erosion from 100 mL of water, not surprising since the grass roots soaked up the water and held the soil into one place. I was able to deduce this hypothesis because I knew the roots from the grass in the soil would help to hold the moisture in the soil. In addition to the amplified effects that can take place without vegetation in an area, these effects also happen much quicker, which is exemplified in the above table which shows that the bottle with grass took much longer than the other bottles to finish spewing water out. One problem we did have is that each bottle did not contain the same amount of soil, which may have thrown off how much erosion. There were a few things that we could of changed, for instance we missed a few days of watering, so when we poured the water on the soil it instantly absorbed, shortening the erosion/ water time.
Conclusion:
This lab can ultimately apply to any unit we have learned throughout this course. Erosion is a growing problem especially due to the amount of deforestation taking place. Some ecosystems are reaching tipping points where forests and vegetation can no longer even be sustained. “A nation that destroys its soil destroys itself.” Franklin Roosevelt, an advocate for environment protection, wrote these words in a letter calling for the creation of local Soil & Water Conservation Districts stating the importance of soil to the nation and how without soil our nation will be in severe trouble. The roots of plants also pump organic matter deep into the soil. Organic matter, formed from the breakdown of living material, is literally the glue that holds soil together. This is why keeping the soil and planting grass, trees, even shrubs are important. I can personally connect because my mom, a homeowner, explains how planting gardens in our backyard can help prevent erosion of our own soil. This lab has shown us the physical effects that deforestation can have on an ecosystem and the physical effects that can be avoided by not clearing forests. If vegetation and trees are kept in an area, the amount of soil erosion that takes place can be kept to a minimum because there are an abundance of roots deep down in the soil. This is demonstrated in the bottle containing only grass. Vegetation, we have observed, keeps a lot of nutrients and moisture in the soil and allows the animals in the ecosystem to prosper. In addition to the amplified effects that can take place without vegetation in an area, these effects also happen much quicker, which is exemplified in the above table which shows that the bottle with grass took much longer than the other bottles to finish watering out. Another advantage to having trees and vegetation in an area that is shown in the soil erosion lab is the filtration of water. The water in the bottle with the grass was much clearer than the water in the other two bottles, showing that ecosystems without excessive deforestation can help clean water of pollutants and other nasty material that may be harmful to organisms or even humans in surrounding areas. I believe the results of the lab were very accurate and if one were to perform a similar lab on a larger scale, for example, a large inhabited forest area, they would find results that would correlate with the ones we found in our lab by testing the speed on runoff. In an article I researched, Jared Diamond, a physiologist at University of California Los Angeles discovered that Iraq, part of the Fertile Crescent in which agriculture started 10,000 years ago, was once the wealthiest, most innovative, most advanced country in the world. But today it was a "basket case", mainly because of "soil problems, salinisation, erosion, coupled with problems of deforestation". This may lead to a collapse in society because more than 99% of the world's food comes from the soil and experts estimate that each year more than (25m acres) of crop land are degraded or lost as rain and wind sweep away topsoil. Deforestation is something that we will probably never be able find a complete solution to, but is something that must be monitored and limited as much as possible because of the many effects it has on the atmosphere and on the ecosystems it is performed in. Other situations this lab can be applied to are the areas around rivers, which are also very important to keep vegetated because erosion can devastate these areas and affect the rivers they surround as well. The erosion of soil on banks surrounding rivers and lakes can be reduced by governmental restricting areas in buffer zones for environmental protection. Overall, the lab shows us that limiting deforestation can benefit the ecosystems in many different ways.
Citations:
Article researched: http://www.theguardian.com/world/2004/feb/14/science.environment
"The Effects of Forest Management on Erosion and Soil Productivity*William J. Elliot, Deborah Page-Dumroese, and Peter R. Robichaud." The Effects of Forest Management on Erosion and Soil Productivity. N.p., n.d. Web. 02 Apr. 2015.