When most people think of soil, they imagine lifeless dirt beneath their feet. In reality, soil is one of the most biologically diverse and active ecosystems on Earth. A single teaspoon of healthy soil can contain billions of microorganisms, thousands of species of fungi, and countless microscopic animals. These organisms form intricate relationships that sustain soil fertility, regulate nutrient cycling, and support plant growth.
This dynamic network of interactions is often described as the soil food web. Much like the food webs that connect animals in forests or oceans, the soil food web represents the flow of energy and nutrients among organisms underground. At its base are decomposers, which are bacteria and fungi that feed on organic matter. Higher up are protozoa, nematodes, and larger organisms like earthworms that graze, hunt, or recycle materials. Together, they create a self-sustaining system that maintains soil health and ecosystem resilience.
Understanding soil life and the soil food web is essential for appreciating soil not merely as a medium for plants but as a living, breathing system central to ecosystem function. By examining its biological components and their interactions, we gain insight into how soils regulate water, recycle nutrients, sequester carbon, and support biodiversity above and below ground.
https://www.youtube.com/watch?v=ErMHR6Mc4Bk
The soil food web describes the network of organisms that live in soil and the relationships between them. It begins with organic inputs, such as dead plant material, leaf litter, and root exudates (compounds secreted by plant roots). These inputs provide energy for soil microbes, which in turn become food for larger soil organisms. At its simplest, the food web can be thought of in levels:
This web is not linear but a complex network of interactions. Nutrients are constantly cycled as organisms eat, digest, and excrete. Carbon, nitrogen, and phosphorus are transformed and redistributed, ensuring that plants have the resources they need to grow. Without the soil food web, organic matter would simply accumulate, nutrients would become locked away, and ecosystems would collapse.
https://www.youtube.com/watch?v=-dhdUoK7s2s
Bacteria are the most abundant organisms in soil, numbering in the billions per gram. Bacterial diversity ensures functional redundancy, meaning that if one group is disturbed, others can often fill its role. This resilience contributes to the soil’s ability to recover from disturbance and maintain ecosystem services.They play critical roles in decomposition, nutrient cycling, and soil structure: