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Ecologyphenomenon

The soil food web

A springtail grazing leaf litter is mostly eating the fungus growing through it.

The community living in soil, from bacteria to the mites that eat the animals that eat the fungi. It is drawn at group level because most of its species have no names — and it is not one web, but a different one in every soil.

A handful of soil holds more organisms than there are people on earth, and the great majority belong to species nobody has described. That is not a rhetorical flourish; it is the practical constraint that shapes how the subject is studied. Soil food webs are almost always drawn as functional groups — bacteria, fungi, bacterial-feeding nematodes, fungal-feeding mites, predatory arthropods — because resolving them to species is beyond what current description supports for most soils. The structure has two entry points rather than one. Some energy enters through roots, as carbon released below ground, feeding organisms that live around them. The rest enters as dead material from above and is worked on by fungi and bacteria, then by the animals that eat those, then by their predators. The two channels differ in speed: the bacterial route is fast and the fungal route slower, and their relative importance shifts with soil conditions and disturbance. The animals in the middle are mostly not eating what they appear to be. A springtail grazing leaf litter is largely consuming the fungal hyphae growing through it. A nematode in the rhizosphere may be eating bacteria rather than roots. This matters for a reason beyond accuracy: when a mite eats a fungus that has taken up nitrogen, some of that nitrogen is excreted in a form plants can use, and grazing the decomposers turns out to be one of the mechanisms that makes nutrients available. Two opposite oversimplifications are worth refusing. Soil is not so finely tuned that every organism is essential — for broad processes like respiring carbon, many different organisms can do the job and losing some changes little. Nor is it interchangeable — nitrification is carried out by a narrow group, and nitrogen fixation by another, and those processes are vulnerable in a way carbon respiration is not. Redundancy is a property of the process, not of the soil.

Early coverage · 43% complete · reviewed 2026-09-04

What this page covers

Bacteria, archaea, fungi, protists, nematodes, mites, springtails, earthworms and their predators. Most soil species have never been formally described, so the web is drawn at group level rather than species level almost everywhere.

Often confused with: One universal soil food web, when composition differs enormously between soils; A tidy pyramid, when most of the interactions are microbial and unresolved

Quick facts

Drawn at group level
Most soil species have never been described
Two entry points
Carbon from roots, and dead material from above
Redundancy varies by job
High for respiring carbon, low for nitrification
Grazing releases nutrients
Eating a fungus that took up nitrogen puts some back in usable form

Who is actually down there

And what each of them is really eating.

The main groups, and what they do
GroupWhat it eatsWhat that does
Bacteria and archaeaSimple compounds, root carbon, litterFast turnover; most of the chemistry
FungiComplex polymers including lignin and celluloseThe slow, difficult breakdown
ProtistsBacteriaReleases nitrogen the bacteria had taken up
NematodesBacteria, fungi, roots, or each otherNot one ecological type — four at least
Springtails and mitesMostly fungi, plus litter and each otherFragmentation, grazing, dispersal of spores
EarthwormsLitter and soil, with its microbesMixing, burrowing, aggregation
Predatory arthropodsThe animals aboveRegulation, and nutrient release

Diagram

The half that is missing from the usual diagram

Dead material, the organisms that work on it, and what comes back.

The half that is missing from the usual diagramDead materialLitter, wood, dung, bodiesFungi and bacteriaDetritivoresmostly eatsPredatorsNutrients released — and taken up again by plantsA detritivore is largely eating the microbes, not the leaf.Simplified: the real web has cannibalism, diets that change with age, and many more links.
The same explanation in words

Dead material — litter, wood, dung and bodies — feeds two routes: fungi and bacteria, and detritivores. An arrow marks that detritivores mostly eat the microbes rather than the material itself. Predators feed on the detritivores. Beneath, nutrients released from the whole process are taken up again by plants. Two notes record that a detritivore is largely eating the microbes rather than the leaf, and that the diagram is simplified: a real web contains cannibalism, diets that change with age, and many more links.

The nematode row is worth pausing on, because "nematodes" is routinely used as though it named an ecological role. It does not. Some eat bacteria, some eat fungi, some feed on plant roots, some are predators of other nematodes, and they are told apart by mouthparts. Treating them as one thing in a food web is like having a single box labelled "vertebrates".

Does it matter how many kinds there are?

For some jobs, hardly. For others, enormously.

Neither "every soil species matters" nor "soil organisms are interchangeable" is right. Broad jobs like respiring carbon have many organisms able to do them; narrow ones like nitrification have very few.

Well supported

Good evidence backs this, though some details remain open.

Relationships between soil biodiversity and ecosystem function are process-specific. Functional redundancy is high for broad processes such as organic matter respiration, and low for narrow processes carried out by restricted taxonomic groups, such as nitrification and nitrogen fixation.

Who this applies to
Soil communities generally; the degree of redundancy differs by process.
Studied in
Bacteria, Fungi, Animalia
Why we rate it this way, and what the caveats are
Well supportedModerate confidence

The process-specific pattern is well supported. Soil biodiversity is poorly described relative to above-ground diversity, so much remains unmeasured.

How far it can be extended

Documented across processes and systems in diversity-function studies.

Caveats

  • Most diversity–function experiments manipulate coarse groups rather than species, so "redundancy" is measured at a coarse resolution.
  • Absence of evidence is common here: soil organisms are far less completely described than above-ground ones.

Still unanswered

  • How much of the apparent redundancy would survive description at species rather than functional-group level.

Last reviewed 2026-09-04

The evidence (2 studies)

The distinction is between broad and narrow processes. Breaking down simple carbon compounds and respiring them is something an enormous range of soil organisms can do, so losing a subset changes the rate rather little — high redundancy. Nitrification, converting ammonium to nitrate, is performed by a comparatively narrow set of microbes; so is nitrogen fixation. Processes carried out by few groups are vulnerable in a way processes carried out by many are not, and a claim that soil biodiversity does or does not matter has to say which process it means.

Related

  • Soil

    The structure this community lives in and builds

  • The rhizosphere

    The busiest few millimetres of it

  • Earthworms

    The one everybody knows, and its context problem

There is no universal soil food web

Which is why the diagram on this page is a type, not a map.

A grassland soil is dominated by bacterial channels; a coniferous forest soil by fungal ones. A waterlogged soil runs on anaerobic processes that barely feature elsewhere. An arable soil disturbed annually has a truncated web with fewer large animals. Published soil food-web diagrams are composites — reasonable for showing what kinds of link exist, and misleading if read as the community under any particular field.

The research behind this page

8 studies, newest first. Each one has a page explaining what it found and what it could not show.

2015Nature

The contentious nature of soil organic matter

Soil organic matter is better described as a continuum of progressively decomposing fragments than as discrete humic macromolecules.

2014Nature

Belowground biodiversity and ecosystem functioning

Soil hosts an extraordinary and incompletely described diversity of organisms.

2009Plant and Soil

Carbon flow in the rhizosphere: carbon trading at the soil–root interface

A substantial share of photosynthetically fixed carbon is released below ground by several distinct processes, of which passive leakage along a concentration gradient is a major one.

2005Annual Review of Ecology, Evolution, and Systematics

Biodiversity and litter decomposition in terrestrial ecosystems

Mixing litter species frequently produces decomposition rates that differ from those predicted by the species alone, in both directions.

2004Ecology Letters

Detritus, trophic dynamics and biodiversity

Detritus supports food webs whose dynamics differ from grazing webs in important respects: the resource does not respond to its consumers, inputs arrive independently of consumption, and the resulting couplings can stabilise or destabilise the wider community depending on structure.

2004Science

Ecological linkages between aboveground and belowground biota

Above-ground and below-ground communities are reciprocally linked.

2004Soil and Tillage Research

A history of research on the link between (micro)aggregates, soil biota, and soil organic matter dynamics

Aggregation operates hierarchically: mineral particles and organic matter bind into microaggregates, which are held into macroaggregates by transient binding agents including roots and fungal hyphae.

1999The American Naturalist

Patterns in the fate of production in plant communities

The share of plant production eaten alive varies enormously between ecosystem types, from a small minority in forests to a large majority in phytoplankton systems.

This page is a stop on a longer route

A guided journey reads several subjects in a deliberate order, with an argument for why one follows another. You can join in the middle.

Where to go from here

Each of these follows from something on this page — a relationship in the evidence, a claim people ask about, or the next mechanism along.

How complete this page is, and what it is still missing

NatureHQ publishes its own gaps. This page is at 43% completeness against what we would call a finished subject, and was last reviewed on 2026-09-04. It carries 5 claims and answers 1 mapped search questions.

  • no research from the last few years is attached — check for newer work
  • more experiments could be explained in plain English
  • no popular claim about this subject has been checked yet
  • Protists are named but not covered in their own right, despite being a major route for nitrogen release.
  • Springtails and mites have no pages of their own; they are treated here as functional groups.
  • Anaerobic soil communities are covered on the peat and anaerobic decomposition pages.