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Earth's Systems / Biological processes / Terrestrial ecosystem functioning / Decomposition / Litter quality, climate and fauna control decay

Litter quality, climate and fauna control decay

What sets how fast litter is decomposed (chemistry, temperature, moisture, sunlight, fauna) and what fraction of litter carbon is respired versus stabilised in soil.

Boundary: where this process starts

Starts with: Initial litter nitrogen and lignin set the decay rate

Boundary: where it ends

Ends after: Respiration returns carbon to the air as CO2; Temperature and moisture regulation of decay

PARTICIPANTSRESOURCESBacteriaFungiSoil faunaLitterMineralsCarbon dioxideDead organicmatterOrganic carbonNitrogenOxygenImpact +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.Impact -3 of 5. Click for details and evidence.60% respiredImpact +3 of 5. Click for details and evidence.40% microbial biomass and reImpact -2 of 5. Click for details and evidence.Impact 02 of 5. Click for details and evidence.Impact 02 of 5. Click for details and evidence.Initial litter nitrogen and lignin set the decay rate: uses up Dead organic matteruses upInitial litter nitrogen and lignin set the decay rate: uses NitrogenSoil animals speed litter mass loss: uses up Dead organic matteruses upFate of decomposed litter carbon: makes Carbon dioxidemakesFate of decomposed litter carbon: uses up Organic carbonuses upRespiration returns carbon to the air as CO2: makes Carbon dioxidemakesRespiration returns carbon to the air as CO2: uses up Oxygenuses upMicrobial residues stabilise on minerals as soil organic matter: uses up Organic carbonuses upTemperature and moisture regulation of decay: uses Carbon dioxidedecay rate set bychemistryDead organic matter: decay rate set by chemistrysets microbial decayspeedNitrogen: sets microbial decay speedmass lost faster throughfragmentationDead organic matter: mass lost faster through fragmentationreleased as respirationgasCarbon dioxide: released as respiration gassplit betweenrespiration and humusOrganic carbon: split between respiration and humusreleased by microbialrespirationCarbon dioxide: released by microbial respirationused up in respirationOxygen: used up in respirationbound intomineral-associated humusOrganic carbon: bound into mineral-associated humusemitted as decayproceedsCarbon dioxide: emitted as decay proceedsStart: Litter quality,climate and faunacontrol decaySTARTStart: Litter quality, climate and fauna control decayEnd: Litter quality,climate and faunacontrol decayENDEnd: Litter quality, climate and fauna control decayInitial litter nitrogenand lignin set thedecay rate📄1Initial litter nitrogen and lignin set the decay rateSoil animals speedlitter mass loss📄1Soil animals speed litter mass lossFate of decomposedlitter carbon📄1Fate of decomposed litter carbonRespiration returnscarbon to the air asCO2👍1📄1Respiration returns carbon to the air as CO2Microbial residuesstabilise on mineralsas soil organic matter📄1 ↗1Microbial residues stabilise on minerals as soil organic matterTemperature andmoisture regulation ofdecay↘📄1Temperature and moisture regulation of decay
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)
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Participant
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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.
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Boundary
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Subprocess
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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

Temperature and moisture regulation of decay

Warmth speeds enzyme-driven decay, dryness slows it, and sunlight can break down litter directly in dry ecosystems; the CO2 released feeds back on warming.

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.

Initial litter nitrogen and lignin set the decay rate
LitterBacteriaFungiDead organic matterNitrogen
Evidence (1) · added by Broad
  • Melillo 1982, Nitrogen and lignin control of hardwood leaf litter decomposition dynamics, Ecology, doi:10.2307/1936780: Hardwood leaf litter mass loss is regulated by initial nitrogen and lignin; high lignin slows decay. (confidence 0.8)
Soil animals speed litter mass loss
Soil faunaDead organic matter
Evidence (1) · added by Broad
  • Wall 2008, Global decomposition experiment shows soil animal impacts on decomposition are climate-dependent, Global Change Biology, doi:10.1111/j.1365-2486.2008.01672.x: Global experiment found soil animals raise decomposition, with effects dependent on climate. (confidence 0.7)
⑂ Fate of decomposed litter carbon
BacteriaFungiOrganic carbonCarbon dioxide
Evidence (1) · added by Broad
  • Manzoni 2012, Environmental and stoichiometric controls on microbial carbon-use efficiency in soils, New Phytologist, doi:10.1111/j.1469-8137.2012.04225.x: Microbial carbon-use efficiency is typically 0.2-0.6 (midpoint about 0.4): 60% respired, 40% into microbial biomass. Estimate with wide range. (confidence 0.5)
Respiration returns carbon to the air as CO2
BacteriaFungiCarbon dioxideOxygen
Evidence (1) · added by Broad
  • Manzoni 2012, Environmental and stoichiometric controls on microbial carbon-use efficiency in soils, New Phytologist, doi:10.1111/j.1469-8137.2012.04225.x: The respired fraction is 1 minus carbon-use efficiency. (confidence 0.6)
Microbial residues stabilise on minerals as soil organic matter
BacteriaFungiMineralsSoil organic matterOrganic carbon
Evidence (1) · added by Broad
  • Cotrufo 2013, The Microbial Efficiency-Matrix Stabilization (MEMS) framework, Global Change Biology, doi:10.1111/gcb.12113: In the MEMS framework, efficient microbes produce residues that bind to minerals and form long-lived organic matter. (confidence 0.7)
↘ Temperature and moisture regulation of decay
BacteriaFungiClimateHeatWaterSunlightCarbon dioxide
Evidence (1) · added by Broad
  • Davidson & Janssens 2006, Temperature sensitivity of soil carbon decomposition and feedbacks to climate change, Nature, doi:10.1038/nature04514: Decomposition rises with temperature (Q10 about 2), with uncertainty over whether stable carbon responds as strongly. (confidence 0.7)