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, students will sample the soil organisms at their field site in two different ways. The activities in this section use the following worksheet:

How Does This Help Our Inquiry?

The data students collect in these activities will likely be central to their research question. Before beginning these activities, remind students of the research question—What is the relationship between the soil's physical properties, environmental and human factors, and soil biodiversity?—or the research question that they posed instead. As they do the activities in this section, ask students to consider how each relates to their research question. Depending on the research question, you may do one or both of these activities in conjunction with the activities in the Soil Properties and Factors That Affect the Soil sections. Rather than introducing all of the activities to students at once, you may want to introduce only one or two at a time, saving the activities in this section for last. Once students have had practice with each of the activities, they should be able to complete multiple activities in one field visit. Doing this once a week, or even once a month, will enhance the activity by allowing students to collect data over an extended period of time and to gain an increased familiarity with their field site.

The activities you choose to combine for your field study should be done together at the same time and place each time they are done. Doing this allows students to control the variables of time and location. You may also give students the opportunity to identify and find ways to control other variables that could affect the outcome.

It is important to give students an opportunity to review and assimilate the data they have collected in their field work. Students should do this following each field study activity. Allowing students to display and discuss their data with other students will help them to relate their data to the research question. Over time, students may want to revise their hypotheses or add activities to their field studies to answer new questions. Students should keep all of their data in their field journals to make it easier to compare data and draw conclusions.

In each of these activities, students will gather data about the critters that live in the soil at the field site. Students can compare this data and the data they gather in Soil Properties. This will help them to see the relationship between soil type and soil biodiversity. Some connections they can make with this data include:

  • How soil compaction affects the critters that can live in the soil.
  • How soil temperature affects the critters that live in the soil.
  • How soil texture/type affects the critters that live in the soil.

Students can also look at the data they gather in these activities and the data they gather in Factors That Affect the Soil. This will help them to see how a variety of factors affect soil life. Some connections they can make with this data include:

  • How soil temperature relates to the numbers and types of critters found in the soil.
  • How food source habitats relate to the critters found in the soil.

Allow students to review the Underground Adventure Field Guide , Meet the Creepy Critters, and/or conduct their own research using some of the resources in the Resources section of the Underground Adventure site. Having this background information will enable students to make more informed hypotheses for each of these activities.

Before students begin these activities, hand out the Soil Biodiversity Overview worksheet and have students place it in their field journals. Students can use this summary sheet to analyze the data they have collected in the field. You may choose to have them do this analysis after each visit to the field or after they have completed several sessions. The Big Picture section of the summary sheet prompts them to make connections between the activities in the different sections.

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 kinds of 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 have students bring an extra pair of shoes to wear while they are doing field work. They can change shoes before going outside and then leave those dirty shoes at the door when they return to the classroom.
  • 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 students bring their field journals, writing utensils, all necessary data sheets, and—if possible—clipboards so they can record their data and observations.

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