The biotic communities of the soil form an intricate living system that can be described as a food web. Food webs describe the relationships among species in an ecosystem, particularly when there is a flow of energy and matter as one organism eats another. This flow is usually represented by arrows.
Did you know? The difference between a food chain and a soil food web is that while a food chain represents one, linear energy pathway through an ecosystem, a food web is more complex and illustrates all of the potential pathways. One may think of a food web as a complex interconnection of food chains.
All food webs are driven by primary producers. Primary producers take the energy of the sun and transform certain inorganic compounds into energy-filled organic compounds; at the same time converting carbon dioxide and minerals into organic compounds by photosynthesis (this is the first trophic level and these organisms are called phototrophs). In most cases, oxygen is also released as a by-product. Primary producers are plants, lichens, moss, photosynthetic bacteria, and algae. The majority of the remaining soil organisms obtain energy and carbon from the organisms in the previous trophic levels by feeding on them. In the soil food web, nutrients are continuously converted from one form to another and made available to the ‘next’ organism. All plants depend on the food web for their nutrition, so one can easily understand the importance of the soil food web for the health of our forest and agricultural fields, for example.
Interesting fact: A few soil microbes called chemoautotrophs, get energy from nitrogen, sulfur, or iron compounds instead of carbon compounds or the sun. Most chemoautotrophs are extremophiles, bacteria or archaea that live in hostile environments. An example of a chemoautotroph is the Nitrosomonas genus. These bacteria oxidize toxic ammonia into nitrite during the nitrogen cycle, increasing the bioavailability of nitrogen to plants which can then be used to produce amino acids and other crucial supplies. Nitrosomonas are useful for bioremediation (a branch of biotechnology that employs living organisms for the removal of contaminants, pollutants, and toxins from soil, water and other environments).
