The Critical Zone

Soil Ecology


Now that we've spent the better part of two lessons studying ecosystem and biome scale processes, I want you to focus especially on soil organisms, soil biodiversity, and the ecology of soils.

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Earthworms play a variety of important roles in soil ecology, including bioturbation by consuming soil particles, digesting the organic content, and recycling the mineral content as castings near burrows.
Source: Wikipedia


For this activity, I want you to complete the paper you have been working on for this lesson (see pages 3 and 4).



For this assignment, you will need to record your work on a word processing document. Your work must be submitted in Word (.doc) or PDF (.pdf) format so I can open it. In addition, documents must be double-spaced and typed in 12 point Times Roman font.

  1. Read the following chapter, located in Library Reserves:
    • Brady, N. C., and Weil (2002). Organisms and Ecology of the Soil. In The Nature and Properties of Soils (13th ed., pp. 449–97). Upper Saddle River, N.J.: Prentice-Hall.
  2. As you read this chapter, finish the three-page report you've been working on for this lesson by answering these questions:
    • What are the primary contributing factors to soil biodiversity? What about at your study site?
    • Consider figure 11.1: can you use this as a template to fill in the details for your site?
    • What role do earthworms fill in pedogenesis at your site? Ants? Microorganisms? Roots?
    • Are there regional or site-specific natural conditions of organic matter content (soil moisture or temperature, for example) that most affect soil biodiversity at your site? How have land use and management practices affected the natural soil biodiversity of your study site?
  3. Re-save your paper.

Submitting your work

Upload your paper to the "Lesson 11 - Biomes" dropbox in Canvas (in the lesson under the Modules tab) by the due date indicated on our Canvas calendar.

Grading Criteria

You will be graded on the quality of your writing. You should not simply write responses to the questions and submit them to me. Instead plan on writing a short stand-alone paragraph (or page or whatever you decide is necessary considering any constraints I might have placed on you) so that anyone can read what you've written and understood it. You should strive to be specific and complete in responding to the questions. Your answers should be analytic, thoughtful and insightful, and should provide an insightful connection between ideas. The writing should be tight and crisp with varied sentence structure and a serious, professional tone.

Check this out . . .

The elite journal Science ran a special section entitled "Soils—The Final Frontier" in June 2004. We will read several articles from the special section in Lesson 12; the following three provide further insight and knowledge on the topic of soil ecology and soil biotic processes.

  • Pennisi, E., 2004, The secret life of fungi, Science, 304, 1620–1622.
  • Wardle, D., et al., 2004, Ecological linkages between aboveground and belowground biota, Science, 304, 1629–1633.
  • Young, I., and Crawford, J., 2004, Interactions and self-organization in the soil-microbe complex, Science, 304, 1634–1637.

To learn about the effects of invasive earthworms on soils see Non-native invasive earthworms as agents of change in northern temperate forests.