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Earth's Systems / Biological processes / Terrestrial ecosystem functioning / Energy transfer through food webs / Trophic efficiency and top-down control

Trophic efficiency and top-down control

How much energy each trophic step passes on (around ten percent), how predators change plant biomass, and the parallel detrital channel that eats dead material.

Boundary: where this process starts

Starts with: Consumers ingest plant or prey tissue

Boundary: where it ends

Ends after: Respired as heat or lost in faeces; Detrital energy channel

PARTICIPANTSRESOURCESHerbivoresPredatorsDecomposersPlantsSoil faunaEnergyOrganic carbonOxygenHeatDead organicmatterImpact +3 of 5. Click for details and evidence.Impact +3 of 5. Click for details and evidence.Impact -3 of 5. Click for details and evidence.90% respired or egestedImpact +3 of 5. Click for details and evidence.10% assimilated into biomassImpact -2 of 5. Click for details and evidence.Impact +3 of 5. Click for details and evidence.Impact +3 of 5. Click for details and evidence.unconsumed plant tissue becoImpact 02 of 5. Click for details and evidence.Consumers ingest plant or prey tissue: uses up Energyuses upConsumers ingest plant or prey tissue: uses up Organic carbonuses upFate of ingested energy: uses EnergyRespired as heat or lost in faeces: uses up Energyuses upRespired as heat or lost in faeces: uses up Oxygenuses upRespired as heat or lost in faeces: makes HeatmakesAssimilated into consumer biomass: uses up Energyuses upAssimilated into consumer biomass: makes Organic carbonmakesPredators suppress herbivores and release plant biomass: uses Organic carbonDetrital energy channel: uses EnergyDetrital energy channel: uses Organic carbonDetrital energy channel: uses Dead organic mattertaken in as foodEnergy: taken in as foodeaten and digested byconsumersOrganic carbon: eaten and digested by consumerssplit between uses andwasteEnergy: split between uses and wastelost as metabolic heatEnergy: lost as metabolic heatconsumed in metabolismOxygen: consumed in metabolismgiven off to theenvironmentHeat: given off to the environmentconverted into newtissueEnergy: converted into new tissuebecomes consumer bodymassOrganic carbon: becomes consumer body massless plant matter eatenOrganic carbon: less plant matter eatenfuels the decomposerfood webEnergy: fuels the decomposer food webcarried into detritusOrganic carbon: carried into detritusenters the detrituspathwayDead organic matter: enters the detritus pathwayStart: Trophicefficiency and top-downcontrolSTARTStart: Trophic efficiency and top-down controlEnd: Trophic efficiencyand top-down controlENDEnd: Trophic efficiency and top-down controlConsumers ingest plantor prey tissue📄1Consumers ingest plant or prey tissueFate of ingested energy📄1Fate of ingested energyRespired as heat orlost in faeces📄1Respired as heat or lost in faecesAssimilated intoconsumer biomass📄1Assimilated into consumer biomassPredators suppressherbivores and releaseplant biomass📄1Predators suppress herbivores and release plant biomassDetrital energy channel↘📄1Detrital energy channel
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

Detrital energy channel

Most terrestrial plant production is not eaten alive but enters the detrital food web of microbes and soil fauna, where grazing on microbes speeds nutrient turnover.

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.

Consumers ingest plant or prey tissue
HerbivoresPredatorsOrganic carbonEnergy
Evidence (1) · added by Broad
  • Lindeman 1942, The trophic-dynamic aspect of ecology, Ecology, doi:10.2307/1930126: Energy enters a trophic level by consumption. (confidence 0.7)
⑂ Fate of ingested energy
HerbivoresPredatorsEnergy
Evidence (1) · added by Broad
  • Lindeman 1942, The trophic-dynamic aspect of ecology, Ecology, doi:10.2307/1930126: About 10% (range 5-20%) of energy becomes biomass of the next level; the rest is respired or egested. 90/10 is a rule-of-thumb midpoint. (confidence 0.55)
Respired as heat or lost in faeces
HerbivoresPredatorsEnergyOxygenHeat
Evidence (1) · added by Broad
  • Lindeman 1942, The trophic-dynamic aspect of ecology, Ecology, doi:10.2307/1930126: Most ingested energy is dissipated as heat or egested. (confidence 0.65)
Assimilated into consumer biomass
HerbivoresPredatorsEnergyOrganic carbon
Evidence (1) · added by Broad
  • Lindeman 1942, The trophic-dynamic aspect of ecology, Ecology, doi:10.2307/1930126: Biomass production is the portion passed on. (confidence 0.65)
Predators suppress herbivores and release plant biomass
PredatorsHerbivoresPlantsOrganic carbon
Evidence (1) · added by Broad
  • Schmitz 2000, Trophic cascades in terrestrial systems: a review of the effects of carnivore removals on plants, American Naturalist, doi:10.2307/3078939: Terrestrial carnivore removal generally raises herbivory and lowers plant biomass (trophic cascade). (confidence 0.75)
↘ Detrital energy channel
DecomposersSoil faunaBacteriaFungiDead organic matterEnergyOrganic carbon
Evidence (1) · added by Broad
  • Wardle 2004, Ecological linkages between aboveground and belowground biota, Science, doi:10.1126/science.1094875: Aboveground and belowground food webs are linked through litter and plant carbon inputs. (confidence 0.7)