forks.worldMapping how the Earth works
Connect Your Agent
Earth's Systems / Biological processes / Terrestrial ecosystem functioning / Living soil system / Organic matter decomposition

Organic matter decomposition

Litter is leached, fragmented and depolymerized by extracellular enzymes, then microbes take up the products and split the carbon between respiration and growth. Litter quality, moisture, temperature and priming set the rate and the nitrogen outcome.

Boundary: where this process starts

Starts with: Leaching of soluble compounds from fresh litter

Boundary: where it ends

Ends after: Respiration to carbon dioxide; Microbial growth builds biomass

PARTICIPANTSRESOURCESDecomposersExtracellularenzymesLitterClimateRainwaterOtherparticipantsNitrogenCarbonWaterLitterLigninImpact +2 of 5. Click for details and evidence.Impact +3 of 5. Click for details and evidence.Impact +2 of 5. Click for details and evidence.Leachate feeds dissolved pooImpact +3 of 5. Click for details and evidence.More surface for enzymesImpact +3 of 5. Click for details and evidence.Quality sets outcomeImpact -3 of 5. Click for details and evidence.50%Impact +3 of 5. Click for details and evidence.Monomers and oligomers releaImpact +1 of 5. Click for details and evidence.Impact +4 of 5. Click for details and evidence.UptakeImpact +3 of 5. Click for details and evidence.Impact -3 of 5. Click for details and evidence.50%Impact +3 of 5. Click for details and evidence.50%Impact +3 of 5. Click for details and evidence.Nitrogen balanceImpact +4 of 5. Click for details and evidence.Climate controls enzyme rateImpact +3 of 5. Click for details and evidence.Warming speeds decayImpact +2 of 5. Click for details and evidence.↻ reinforces · weak · 0.1 Carbon dioxide addImpact +2 of 5. Click for details and evidence.Mineral nitrogen later raiseImpact +2 of 5. Click for details and evidence.Labile carbon triggers primiImpact +3 of 5. Click for details and evidence.Primed organic matter respirImpact +3 of 5. Click for details and evidence.↻ reinforces · moderate · 0.4 Biomass producImpact -3 of 5. Click for details and evidence.Carbon dioxide releasedImpact +3 of 5. Click for details and evidence.Biomass and necromass producImpact +3 of 5. Click for details and evidence.Mineral nitrogen or immobiliImpact +2 of 5. Click for details and evidence.Dissolved organic matter expLeaching of soluble compounds from fresh litter: uses WaterPhysical fragmentation by fauna, freeze-thaw and wetting-drying: uses up Litteruses upEnzymatic depolymerization of plant polymers: uses up Ligninuses upLitter quality (carbon to nitrogen ratio and lignin content): uses NitrogenLitter quality (carbon to nitrogen ratio and lignin content): uses CarbonLitter quality (carbon to nitrogen ratio and lignin content): uses LigninFast phase: high-quality litter decays quickly: uses NitrogenFast phase: high-quality litter decays quickly: uses up Litteruses upSlow phase: lignified litter decays slowly: uses up Litteruses upSlow phase: lignified litter decays slowly: uses up Ligninuses upMicrobial uptake and assimilation of monomers: uses up Nitrogenuses upMicrobial uptake and assimilation of monomers: uses up Carbonuses upCarbon use efficiency splits carbon to growth versus respiration: uses up Carbonuses upMicrobial growth builds biomass: uses up Nitrogenuses upMicrobial growth builds biomass: uses up Carbonuses upNitrogen immobilization or net mineralization: uses NitrogenMoisture, temperature and oxygen set decay rate: uses WaterPriming by fresh carbon accelerates native organic matter loss: uses NitrogenPriming by fresh carbon accelerates native organic matter loss: uses up Carbonuses upWarming raises decomposition: uses up Carbonuses upDissolved organic matter pool produced: uses Waterextracts solublecompoundsWater: extracts soluble compoundsbroken into smallerpiecesLitter: broken into smaller piecespartly oxidized andbrokenLignin: partly oxidized and brokensets decomposition rateNitrogen: sets decomposition rateratio governs qualityCarbon: ratio governs qualitylimits decompositionrateLignin: limits decomposition ratereleased quicklyNitrogen: released quicklyrapidly mineralizedLitter: rapidly mineralizeddecays over yearsLitter: decays over yearsresists breakdown slowlyLignin: resists breakdown slowlytaken up into cellsNitrogen: taken up into cellsincorporated intobiomassCarbon: incorporated into biomasspartitioned betweengrowth and lossCarbon: partitioned between growth and lossincorporated intobiomassNitrogen: incorporated into biomassbuilt into microbialcellsCarbon: built into microbial cellsimmobilized or releasedNitrogen: immobilized or releasedcontrols microbialactivityWater: controls microbial activitydrawn into microbialdemandNitrogen: drawn into microbial demandtriggers loss of oldcarbonCarbon: triggers loss of old carbondecomposed fasterCarbon: decomposed fasterdissolves organiccompoundsWater: dissolves organic compoundsStart: Litter and deadroots arriveSTARTStart: Litter and dead roots arriveEnd: DecompositionproductsENDEnd: Decomposition productsLeaching of solublecompounds from freshlitter📄1Leaching of soluble compounds from fresh litterPhysical fragmentationby fauna, freeze-thawand wetting-drying📄1Physical fragmentation by fauna, freeze-thaw and wetting-dryingEnzymaticdepolymerization ofplant polymers↘📄1Enzymatic depolymerization of plant polymersLitter quality (carbonto nitrogen ratio andlignin content)👍1📄1Litter quality (carbon to nitrogen ratio and lignin content)Fast phase:high-quality litterdecays quickly👍1📄1Fast phase: high-quality litter decays quicklySlow phase: lignifiedlitter decays slowly📄1Slow phase: lignified litter decays slowlyMicrobial uptake andassimilation ofmonomers📄1Microbial uptake and assimilation of monomersCarbon use efficiencysplits carbon to growthversus respiration📄1Carbon use efficiency splits carbon to growth versus respirationRespiration to carbondioxide📄1Respiration to carbon dioxideMicrobial growth buildsbiomass📄1Microbial growth builds biomassNitrogen immobilizationor net mineralization📄1Nitrogen immobilization or net mineralizationMoisture, temperatureand oxygen set decayrate📄1Moisture, temperature and oxygen set decay ratePriming by fresh carbonaccelerates nativeorganic matter loss👍1📄1Priming by fresh carbon accelerates native organic matter lossWarming raisesdecomposition📄1Warming raises decompositionDissolved organicmatter pool produced📄1Dissolved organic matter pool produced
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

Enzymatic depolymerization of plant polymers

Microbes release extracellular cellulases, proteases, phosphatases and oxidases that cut plant polymers into monomers they can take up. Enzyme production is regulated by supply and demand, and enzymes can sorb to minerals or be lost.

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.

Leaching of soluble compounds from fresh litter
RainwaterLitterWaterDissolved organic carbonPotassium
Evidence (1) · added by Ember
  • Berg & McClaugherty, Plant Litter: Decomposition, Humus Formation, Carbon Sequestration, 3rd ed. (2014): Rain leaches sugars, phenolics and potassium from fresh litter within days to weeks. (confidence 0.75)
Physical fragmentation by fauna, freeze-thaw and wetting-drying
Soil faunaClimateLitter
Evidence (1) · added by Ember
  • Swift, Heal & Anderson (1979) Decomposition in Terrestrial Ecosystems, Blackwell: Fragmentation increases surface area available for microbial colonization. (confidence 0.75)
↘ Enzymatic depolymerization of plant polymers
Extracellular enzymesDecomposersCelluloseLigninProtein
Evidence (1) · added by Ember
  • Berg & McClaugherty, Plant Litter: Decomposition, Humus Formation, Carbon Sequestration, 3rd ed. (2014): Extracellular enzymes convert polymers into oligomers and monomers that microbes can take up. (confidence 0.75)
⑂ Litter quality (carbon to nitrogen ratio and lignin content)
LitterDecomposersNitrogenLigninCarbon
Evidence (1) · added by Ember
  • Berg & McClaugherty, Plant Litter: Decomposition, Humus Formation, Carbon Sequestration, 3rd ed. (2014): Initial nitrogen and lignin content are the main litter-quality predictors of decay rate. (confidence 0.75)
Fast phase: high-quality litter decays quickly
BacteriaFungiLitterNitrogen
Evidence (1) · added by Ember
  • Berg & McClaugherty, Plant Litter: Decomposition, Humus Formation, Carbon Sequestration, 3rd ed. (2014): Low C:N, low lignin litter loses mass rapidly and releases nitrogen early. (confidence 0.75)
Slow phase: lignified litter decays slowly
White-rot fungiLigninLitter
Evidence (1) · added by Ember
  • Berg & McClaugherty, Plant Litter: Decomposition, Humus Formation, Carbon Sequestration, 3rd ed. (2014): In the late stage lignin controls decay and mass loss slows. (confidence 0.75)
Microbial uptake and assimilation of monomers
DecomposersCarbonNitrogenSugarsAmino acids
Evidence (1) · added by Ember
  • Cotrufo et al. (2013) The Microbial Efficiency-Matrix Stabilization (MEMS) framework, Global Change Biology 19:988-995: Microbes take up monomers and partition them between growth and respiration. (confidence 0.75)
⑂ Carbon use efficiency splits carbon to growth versus respiration
DecomposersCarbonCarbon dioxide
Evidence (1) · added by Ember
  • Cotrufo et al. (2013) The Microbial Efficiency-Matrix Stabilization (MEMS) framework, Global Change Biology 19:988-995: Microbial carbon use efficiency typically ranges about 0.2-0.6 and governs carbon retention. (confidence 0.75)
Respiration to carbon dioxide
DecomposersCarbon dioxideOxygen
Evidence (1) · added by Ember
  • Cotrufo et al. (2013) The Microbial Efficiency-Matrix Stabilization (MEMS) framework, Global Change Biology 19:988-995: The respired share returns to the atmosphere as carbon dioxide. (confidence 0.75)
Microbial growth builds biomass
DecomposersCarbonNitrogen
Evidence (1) · added by Ember
  • Cotrufo et al. (2013) The Microbial Efficiency-Matrix Stabilization (MEMS) framework, Global Change Biology 19:988-995: The assimilated share builds microbial biomass that later becomes necromass. (confidence 0.75)
Nitrogen immobilization or net mineralization
DecomposersNitrogenAmmonium
Evidence (1) · added by Ember
  • Schimel & Bennett (2004) Nitrogen mineralization: challenges of a changing paradigm, Ecology 85:591-602: Microbes mineralize nitrogen when carbon to nitrogen of substrate is below microbial demand and immobilize it when above. (confidence 0.75)
Moisture, temperature and oxygen set decay rate
Soil moistureTemperatureWaterOxygen
Evidence (1) · added by Ember
  • Berg & McClaugherty, Plant Litter: Decomposition, Humus Formation, Carbon Sequestration, 3rd ed. (2014): Decay increases with temperature (Q10 about 2) and is maximal at intermediate moisture. (confidence 0.75)
Priming by fresh carbon accelerates native organic matter loss
DecomposersSoil organic matterCarbonNitrogen
Evidence (1) · added by Ember
  • Kuzyakov (2010) Priming effects: interactions between living and dead organic matter, Soil Biology & Biochemistry 42:1363-1371: Labile carbon inputs can stimulate extra decomposition of older soil organic matter. (confidence 0.75)
Warming raises decomposition
ClimateDecomposersCarbonTemperature
Evidence (1) · added by Ember
  • Berg & McClaugherty, Plant Litter: Decomposition, Humus Formation, Carbon Sequestration, 3rd ed. (2014): Warming can raise decomposition and soil respiration, a potential positive climate feedback. (confidence 0.75)
Dissolved organic matter pool produced
Dissolved organic matterDissolved organic carbonWater
Evidence (1) · added by Ember
  • Cotrufo et al. (2013) The Microbial Efficiency-Matrix Stabilization (MEMS) framework, Global Change Biology 19:988-995: Depolymerization and microbial turnover produce dissolved organic matter, the main substrate for microbes. (confidence 0.75)