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The Soil Food Web
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What It Is and A Few Interesting Facts

  • The soil food web is a simple way of referring to the functions of the soil biological community. (Click here to view soil food web graphic.) It sounds simple, but it is actually incredibly complex. First of all, think of all the organisms that are a part of the soil biological community: bacteria, algae, cyanobacteria, fungi, protozoa, nematodes, and arthropods. Plants, larger animals (such as ground squirrels, badgers, and jackrabbits), and many other organisms are also part of this biological community. The organisms that live in the soil all or part of the time are incredibly diverse. They also are incredibly busy. Up to 90 percent of the total productivity of rangelands occurs in the soil.
  • Soil Economics 101: Plants, algae, cyanobacteria, lichens, bryophytes, and photosynthetic bacteria use the sun’s energy to fix atmospheric carbon to sugar form and are the primary producers that fuel the food web.  Other soil organisms obtain energy and nutrients by feeding on primary producers and each other. These organisms are the consumers. The mass of dead organisms (or pieces and parts thereof) in the soil is referred to as "soil organic matter." You can think of soil organic matter as a bank, storing currency (nutrients and energy) that help both producers and consumers prosper.
  • Soil food webs are wonderful in their complexity. But like any complex system, the whole is greater than the sum of its parts, and if parts are removed, well, the whole thing disintegrates. Think of your car: you can do without a windshield wiper for a while, or a window, or a glovebox cover. But start removing tires, the steering wheel, the clutch, the brakes, and you won’t be going very far. The soil food web functions in a similar way. Nobody may miss a few ants, a little algae. But if key organisms or multiple groups disappear, you’ve got a problem.

Why It Is Important

  • Rangeland plants depend upon the food web for their nutrition. In turn, they provide food and habitat for all sorts of wildlife and domestic animals. They also make rangelands a beautiful place to spend a day. So, in the long run, this "invisible" soil food web makes our lives pretty darn pleasant.
  • Nutrients in decomposing material are converted to forms that are readily used by plants. The plants, in turn, tie up the nutrients, preventing them from accumulating in water and soil (sort of a "natural" form of pollution control). In a nutshell, if allowed to do so, the system will maintain itself.
  • All those organisms in the soil moving, eating, digesting, excreting, and dying, enhances the soil structure, stability, porosity, infiltration, and aeration. So what does that mean? It means that the soil biological community improves the condition of the soil. The bottom line is that they make the soil a better place to live, which translates into stronger, healthier plants and a more stable and attractive environment for humans and wildlife.

Learn More!

Ingham, Elaine R. 1998. The soil biology primer, the food web. USDA, Natural Resources Conservation Service, Soil Quality Institute.

Ingham, Elaine R. 1998. The soil biology primer, the food web and soil health. USDA, Natural Resources Conservation Service, Soil Quality Institute.

Stanton, N.L. 1988. The underground in grasslands. Ann. Rev. Ecol. Syst. 19: 573-589.

Whitford, Walter G. 1986. Decomposition and nutrient cycling in deserts. pp. 93-117 in Pattern and Process in Desert Ecosystems. W.G. Whitford (ed). University of New Mexico Press. Albuquerque, NM.

Whitford, Walter G. and Jeffrey E. Herrick. 1996. Maintaining soil processes for plant productivity and community dynamics. pp. 33-37 in Rangelands in a Sustainable Biosphere. Proceedings of the Fifth International Rangeland Congress. Vol. II. Society for Range Mgmt. Denver, CO.

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