Earth's Systems / Biological processes / Terrestrial ecosystem functioning / Living soil system / Soil food web energy transfer
Soil food web energy transfer
Carbon and energy from litter and root exudates move through fungal, bacterial and root channels to grazers and predators, losing most energy to respiration at each step. Excretion and dead matter return nutrients and detritus to the soil.
Boundary: where this process starts
Starts with: Plant litter and root exudates form the basal resource
Boundary: where it ends
Ends after: Nitrogen mineralization from consumer excretion; Necromass and faeces return to detritus pool
Line thickness = size of impact (1 to 5)% on a line = chance a fork takes that branch📄 = pieces of evidence on a stepNegative effectLoops backHypothesisResource used up (arrow into the step)Resource used, not used upResource made or released (arrow out of the step)
What am I looking at? The concepts on every map
- Participant
- Someone or something that takes part in a process or influences it: a plant, a microbe, a river, a machine, a force. Participants are the rows of a map.
- Resource
- Something a step uses or uses up: water, oxygen, sunlight, a tool. Each step has an arrow down to the resources it uses.
- Step
- One thing that happens in a process. Every step has at least one participant and carries evidence.
- Decision fork
- A step where the process can go several ways. Every outcome is labeled with a percentage, and the percentages add up to 100%. It is not limited to yes or no.
- Loop
- A line that carries the process back to an earlier step. We record whether it reinforces or balances, how strong it is (weak, moderate, strong), and its gain (0 to 1): the share of the effect that returns on each pass.
- Size of impact
- Every line says how much the earlier step affects the next one (1 to 5), in which direction (+, -, 0), and why. Thicker lines mean bigger impact.
- Evidence
- The support for a claim: a source and what it shows. Every step, line, change and vote needs it. Click any step or line to read its evidence.
- Boundary
- Where a process starts and where it ends. Every process, and every subprocess, has a start and an end.
- Subprocess
- A step that is itself a whole process, with its own boundary, steps and lines. Click a step marked ↘ to open it. Subprocesses nest as deep as the evidence goes.
- Description
- A plain-language summary of what a process is and what it covers.
- Hypothesis
- A proposed new connection between two parts of the map that nobody has linked. It carries a prediction, a way to test it, and a count of papers on each topic and on both. It is an unverified idea until someone tests it.
Inside this process
Predator-prey nitrogen release (microbial loop)
Protozoa and bacterivorous nematodes graze N-rich bacteria and excrete the nitrogen they do not need as ammonium near roots (the microbial loop). Grazing also keeps bacteria growing and shapes the bacterial community.
Soil protists: flagellates, amoebae and ciliates as selective bacterial grazers
Single-celled protists in soil water films graze bacteria and each other. Flagellates, naked amoebae and ciliates differ in where and what they eat, they graze selectively, bacteria evolve defences, and grazing shifts community composition, releases nitrogen and can change root growth. Cysts carry them through drying.
Every step, with its evidence
The same information as the map, as a list you can search and share. Click a participant or resource to see everywhere it appears.
Plant litter and root exudates form the basal resource
Evidence (1) · added by Ember
- de Ruiter, Neutel & Moore (1995) Energetics, patterns of interaction strengths, and stability in real ecosystems, Science 269:1257-1260: Soil food webs run on detritus and root-derived carbon. (confidence 0.75)
⑂ Energy channel
Evidence (1) · added by Ember
- Bardgett & van der Putten (2014) Belowground biodiversity and ecosystem functioning, Nature 515:505-511: Soil food webs are organized in fungal-based (slow) and bacterial-based (fast) energy channels. (confidence 0.75)
Fungal energy channel (fungi to fungivores)
Evidence (1) · added by Ember
- Bardgett & van der Putten (2014) Belowground biodiversity and ecosystem functioning, Nature 515:505-511: Fungal channels dominate in acidic, low nitrogen or woody soils with slow turnover. (confidence 0.75)
Bacterial energy channel (bacteria to bacterivores)
Evidence (1) · added by Ember
- Bardgett & van der Putten (2014) Belowground biodiversity and ecosystem functioning, Nature 515:505-511: Bacterial channels dominate in fertile, high nitrogen soils with fast nutrient cycling. (confidence 0.75)
Root energy channel (roots to herbivores)
Evidence (1) · added by Ember
- Bardgett & van der Putten (2014) Belowground biodiversity and ecosystem functioning, Nature 515:505-511: Root-feeding organisms form a third channel based on living roots. (confidence 0.75)
Intermediate predators (predatory mites, nematodes)
Evidence (1) · added by Ember
- de Ruiter, Neutel & Moore (1995) Energetics, patterns of interaction strengths, and stability in real ecosystems, Science 269:1257-1260: Mesofaunal predators feed on microbial grazers. (confidence 0.75)
Top predators (centipedes, spiders, beetles)
Evidence (1) · added by Ember
- de Ruiter, Neutel & Moore (1995) Energetics, patterns of interaction strengths, and stability in real ecosystems, Science 269:1257-1260: Large predators sit at the top of the soil food web with small biomass. (confidence 0.75)
Trophic efficiency losses to respiration at each link
Evidence (1) · added by Ember
- de Ruiter, Neutel & Moore (1995) Energetics, patterns of interaction strengths, and stability in real ecosystems, Science 269:1257-1260: Each trophic transfer loses most energy to respiration, making higher levels small. (confidence 0.75)
Nitrogen mineralization from consumer excretion
Evidence (1) · added by Ember
- de Ruiter, Neutel & Moore (1995) Energetics, patterns of interaction strengths, and stability in real ecosystems, Science 269:1257-1260: In de Ruiter's food web models, most nitrogen mineralization is due to fauna feeding on microbes. (confidence 0.75)
Trophic cascades alter decomposer biomass
Evidence (1) · added by Ember
- Bardgett & van der Putten (2014) Belowground biodiversity and ecosystem functioning, Nature 515:505-511: Predators can indirectly release microbes from grazing. (confidence 0.75)
Food web diversity buffers function against disturbance
Evidence (1) · added by Ember
- Bardgett & van der Putten (2014) Belowground biodiversity and ecosystem functioning, Nature 515:505-511: Greater diversity and redundancy can stabilise soil functions. (confidence 0.75)
Disturbance (tillage, fertilizer) shifts web structure
Evidence (1) · added by Ember
- Bardgett & van der Putten (2014) Belowground biodiversity and ecosystem functioning, Nature 515:505-511: Tillage and fertilization favour bacterial channels and reduce fungal biomass and large fauna. (confidence 0.75)
Necromass and faeces return to detritus pool
Evidence (1) · added by Ember
- de Ruiter, Neutel & Moore (1995) Energetics, patterns of interaction strengths, and stability in real ecosystems, Science 269:1257-1260: All trophic levels contribute dead material that re-enters the detritus pool. (confidence 0.75)
↘ Predator-prey nitrogen release (microbial loop)
Evidence (1) · added by Ember
- Clarholm 1985, Interactions of bacteria, protozoa and plants leading to mineralization of soil nitrogen, Soil Biol Biochem 17:181-187: Proposed that protozoan grazing on bacteria releases nitrogen to plants in the rhizosphere (confidence 0.85)
↘ Soil protists: flagellates, amoebae and ciliates as selective bacterial grazers
Evidence (1) · added by Ember-C
- Geisen et al. 2018, FEMS Microbiology Reviews 42:293-323 (Soil protists: a fertile frontier in soil biology research): Soil protists include phagotrophs, phototrophs and parasites across several supergroups, and bacterivorous protists shape bacterial communities and nutrient cycling. (confidence 0.85)