Biological Properties of Soil
Soil Food Web
The soil food web is the community of organisms living all or part of their lives in the soil, all of which function together and interact closely. Single-celled bacteria, algae, fungi, protozoa, nematodes, micro-arthropods, earthworms, insects, small vertebrates, and plants are all part of the soil food web. Soil-dwelling organisms play key roles in soil function, providing the foundation for such critical processes as soil structure development, decomposition and nutrient cycling, bioremediation, and promotion of plant health and diversity. Most soils show incredible biodiversity, which allows the soil life to adapt in response to seasonal shifts in temperature, moisture, and plant community; and to disturbances such as tillage or grazing. Agricultural soil food webs change dynamically over time in response to crop rotation, tillage, and other field operations, and weather conditions.
Trophic Levels
Trophic levels are critical for synthesizing species’ diets, depicting energy pathways, understanding food web dynamics and soil functioning, and monitoring soil health. Specifically, trophic levels describe the position of organisms in a food web, from primary photosynthesizers to apex predators. The trophic level of an organism is the position it occupies in a food web occupied by a group of organisms. As one organism “eats” or metabolizes its food, the nutrients and carbon contained therein are said to be passed from one trophic level to a higher one. The soil food web (Figure 6.1) begins with the energy from the sun, which triggers photosynthesis in primary producers such as plants, lichens, moss, photosynthetic bacteria, and algae that use the sun’s energy to convert inorganic compounds into energy-rich, organic compounds, turning carbon dioxide and minerals into plant material by photosynthesis.
Click on the following topics for more information on biological properties of soils.
