Soil Biodiversity

Soil Biodiversity Overview

There is plenty of food and water to be found in the soil, the climate is stable, and there are great places to hide from predators. For all these reasons, soil is full of living creatures. In fact, so many different kinds of organisms live in soil that thousands of new species are discovered each year.

Biodiversity means the number and variety of living organisms that are found in an area. Generally, the higher the degree of biodiversity, the healthier an ecosystem tends to be. The healthier the soil, the more life that ecosystem can support, resulting in a greater degree of biodiversity. In these activities, we'll investigate the biodiversity of the soil in your field site.

What Are We Doing?

In these two activities, you will sample the soil organisms at your field site in two different ways. The activities in this section use the following worksheet:

Want more information before you get started? Read on to find out:

How Does This Help Our Inquiry?

Remember our research question—What is the relationship between the soil's physical properties, environmental and human factors, and soil biodiversity?—or the research question you asked instead. In each of these activities, you will gather data about the critters that live in the soil at your field site. Look at the data you gather in these activities and the data you gather in Soil Properties. This will help you to see the relationship between the type of soil in your field site and the biodiversity that you find there. Look at the data you gather in these activities and the data you gather in Factors That Affect the Soil. This will help you to see how a variety of different environmental and human factors affect the critters that live in the soil. Be sure you do these activities at the same time and place so you can compare the data you get. Do these activities as many times as you can. The more data you collect, the easier it will be to see the relationships between soil biodiversity, environmental factors, and soil type. Keep all your data in your field journal so that you can easily compare and draw conclusions.

Before you begin these activities, print the Soil Biodiversity Overview worksheet and place it in your field journal. After you complete each activity, use this sheet to summarize and analyze your results. When you have completed all the activities in this section, fill in the Big Picture section of the overview worksheet.

What Do We Need to Know?

Giving Back to Soil
All critters that live in the soil play a role in keeping it healthy. Ants bring soil to the surface and food down into the soil, mixing up the soil and enriching it with new nutrients. Decomposers like the millipede help to break down dead plants and animals, returning those nutrients to the soil. As earthworms tunnel through the soil, they mix in organic matter and break up clumps of soil while creating spaces for air and water in the soil. Each of these critters, as well as many others found in the soil, gives something back to the soil, making it a healthier place for other organisms.

Classifying Critters
Scientists classify all living organisms, or sort them into groups based on their properties. Organisms are first sorted into large groups by looking at just a few main properties. They are then sorted into smaller and smaller groups as more properties are considered. Classifying organisms in this way allows scientists from around the world to call each unique creature by the same unique name, regardless of what language they speak. It also helps them to keep track of the many diverse and amazing creatures with which we share our planet.

Most of the soil critters that you will see are invertebrates. Invertebrates have one important characteristic in common—they have no backbone. Some of the invertebrates you will see are arthropods. Although all arthropods are different, they all have jointed legs and a hard outer skeleton called an exoskeleton. Insects are arthropods that have three body regions; a head, a thorax, and an abdomen. They have one pair of antennae on the head and they have six legs that are attached to the thorax. Arachnids are arthropods with eight legs, one or two body regions, no antennae, and no wings.

Why Is This So Important, Anyway?

The creatures we find in the soil can help to make the soil healthier. They can also help us to judge how healthy the soil is. Healthy soil tends to have lots of different organisms living in it. The health of the soil is very important to us. We depend on it for food, clothes, and many other things we use every day. By understanding the creatures that live in the soil, we can better understand the soil itself and we can work to keep it healthy.

Understanding the creatures that live in the soil can also help us to make important decisions. If you were going to plant a garden, for example, you would want to plant it in soil that was full of earthworms, but not full of slugs! The farmers who grow the food we eat must understand the critters that live in the soil in order to have good crops.

General Tips

  • Be ready for dirt! You may want to bring an extra pair of shoes to wear for your field work. You can change shoes before going outside and then leave those dirty shoes at the door when you come back in.
  • Remember to do the soil study at the same time and place each time.
  • Be prepared to do the activities in Soil Properties and Factors That Affect the Soil at the same time and place as these activities.
  • Be sure to bring your field journal so you can record your observations and all the data you gather.

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Here’s a fun, easy way to check out the soil biodiversity in your area: Rock Flip!