Question: Why does it matter if I stay on the trail while hiking in the woods and parks?
Answer: People love to be outdoors, and soil is an important contributor to a good outing, whether you are hiking, mountain biking, painting, or just enjoying nature. But humans can have significant impacts on the soil. When we walk on soil, our body weight compresses the soil. Soil compaction occurs when soil particles are pressed together, reducing the space between them. This has several effects.
In the figure to the right, you can see that soil particles come in various sizes. In between the particles are open spaces, or “pores”. These pores allow air and water to move through the soil. Air is important because microbes living in soil pores use some of the nitrogen and other elements from air as “food”. And, soil holds water and nutrients for plants to use in the same pores. You can see in the figure that compressing the soil limits the amount of air and water soil can hold—and that’s not good for soil microbes or the plants living in the soil.
Heavily compacted soils contain few large pores. This means that water does not move as easily through those soils. Large pores are more effective in moving water through the soil when it is saturated than smaller pores. A very compacted soil will actually repel water during a rainfall, and this vital water will run off into nearby streams and lakes. So, even though it may rain, the plants in the woods remain “thirsty”.
-Answered by Mary Beth Adams, U.S. Forest Service
To learn more, view SSSA’s Soils Support Recreation video.
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More educational materials can be found on various SSSA websites:
http://soils4teachers.org/ (K-12 Lesson Plans and Activities)
http://soils4kids.org (Just for kids!)
http://soils.org/iys (International Year of Soils, with a coloring book and monthly ideas for teachers and scientists!)