Soil Food Web

The soil food web is the network of feeding relationships among plant roots, microorganisms and soil animals. It sustains nutrient cycling by decomposing organic matter, transforming nutrients into plant-available forms and retaining them within living biomass and stable soil organic matter.

Organic matter enters the web

Forest litter, dead roots, animal remains and wastes supply detritus, while living roots release carbon compounds into the soil.

• Bacteria and fungi chemically break down complex organic material through decomposition.
• Detritivores such as earthworms and arthropods fragment litter, increasing the surface available for microbial action.

Nutrients are transformed and transferred

During mineralisation, decomposers convert organically bound nutrients into inorganic forms that plants can absorb. Nutrients then move through the web as organisms consume microbes, detritus and one another.

• Microorganisms temporarily incorporate nutrients into their biomass through immobilisation, reducing immediate losses by leaching.
• Microbial grazers release part of the nutrients held in microbial cells back into the soil in available forms.
• Predators influence decomposer and grazer populations, helping regulate the rate and location of nutrient release.

The forest nutrient loop is completed

Plant roots absorb released nutrients, and mycorrhizal fungi extend the effective soil volume from which many plants obtain mineral nutrients. Plants return these nutrients to the soil through litter, root turnover and death, completing the cycle.

• Aggregation promoted by roots, fungi and soil animals helps protect soil organic matter and maintain soil structure.
• A diverse food web provides multiple pathways for decomposition and nutrient transfer, supporting forest productivity and recovery from disturbance.