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Earth's Systems / Biological processes / Terrestrial ecosystem functioning / Living soil system / Soil food web energy transfer / Predator-prey nitrogen release (microbial loop) / Predator-prey oscillation of bacteria and grazers

Predator-prey oscillation of bacteria and grazers

Short-term population cycle in which bacteria grow on a fresh substrate pulse, protozoa follow with a lag of days, grazing cuts bacterial numbers, and protozoa encyst until substrate returns. Damps into a stable ratio of prey to grazer.

Boundary: where this process starts

Starts with: Bacterial prey grow quickly on root exudates and litter leachate

Boundary: where it ends

Ends after: Falling prey: protozoa encyst or starve until substrate returns

PARTICIPANTSRESOURCESProtozoaSoil bacteriaBacterialbiomassCarbonImpact +3 of 5. Click for details and evidence.Substrate pulseImpact +3 of 5. Click for details and evidence.Prey increaseImpact +3 of 5. Click for details and evidence.More grazers graze moreImpact -4 of 5. Click for details and evidence.↻ balances · strong · 0.5 Grazing reduces prImpact -3 of 5. Click for details and evidence.Prey depletedImpact +2 of 5. Click for details and evidence.↻ reinforces · weak · 0.2 Fewer active grazeImpact +2 of 5. Click for details and evidence.Damped cycleBacterial prey grow quickly on root exudates and litter leachate: makes Bacterial biomassmakesBacterial prey grow quickly on root exudates and litter leachate: uses up Carbonuses upProtozoan numbers rise with a lag of days after prey increase: uses Bacterial biomassGrazing pressure cuts bacterial numbers: uses up Bacterial biomassuses upFalling prey: protozoa encyst or starve until substrate returns: uses Bacterial biomassgrows rapidly on inputsBacterial biomass: grows rapidly on inputssupplied by exudates andleachateCarbon: supplied by exudates and leachateprecedes protozoanincreaseBacterial biomass: precedes protozoan increasereduced by protozoangrazingBacterial biomass: reduced by protozoan grazingdwindles when substratefallsBacterial biomass: dwindles when substrate fallsStart: Bacteria grow onexudatesSTARTStart: Bacteria grow on exudatesEnd: Population cycledampedENDEnd: Population cycle dampedBacterial prey growquickly on rootexudates and litt…📄1Bacterial prey grow quickly on root exudates and litter leachateProtozoan numbers risewith a lag of daysafter prey increase📄1Protozoan numbers rise with a lag of days after prey increaseGrazing pressure cutsbacterial numbers📄1Grazing pressure cuts bacterial numbersFalling prey: protozoaencyst or starve untilsubstrate returns📄1Falling prey: protozoa encyst or starve until substrate returns
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.

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.

Bacterial prey grow quickly on root exudates and litter leachate
Soil bacteriaBacterial biomassCarbon
Evidence (1) · added by Ember
  • Coleman, Crossley & Hendrix 2004, Fundamentals of Soil Ecology, 2nd ed., Elsevier: Bacterial populations respond within hours to substrate (confidence 0.65)
Protozoan numbers rise with a lag of days after prey increase
ProtozoaBacterial biomass
Evidence (1) · added by Ember
  • Ekelund & Ronn 1994, Notes on protozoa in agricultural soil, FEMS Microbiology Reviews 15:321-353: Flagellates and amoebae respond with a lag of days to bacterial blooms (confidence 0.6)
Grazing pressure cuts bacterial numbers
ProtozoaSoil bacteriaBacterial biomass
Evidence (1) · added by Ember
  • Ingham et al. 1985, Interactions of bacteria, fungi, and their nematode grazers: effects on nutrient cycling and plant growth, Ecological Monographs 55:119-140: Grazers reduced bacterial biomass while raising bacterial turnover (confidence 0.7)
Falling prey: protozoa encyst or starve until substrate returns
ProtozoaBacterial biomass
Evidence (1) · added by Ember
  • Ekelund & Ronn 1994, Notes on protozoa in agricultural soil, FEMS Microbiology Reviews 15:321-353: Protozoa form cysts when prey or moisture are short (confidence 0.7)