Decomposition
Breakdown of dead plant and animal material by fragmentation, leaching and microbial enzymes, releasing CO2 and mineral nutrients and forming soil organic matter.
Boundary: where this process starts
Starts with: Leaching of soluble compounds from litter
Boundary: where it ends
Ends after: Microbial catabolism and CO2 release; Respired as CO2
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
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.
Litter quality (lignin:N) sets the decay trajectory
How litter chemistry sets the speed and phases of decay: an early phase on soluble sugars and cellulose, then a late phase limited by lignin and by nitrogen supply, with litter N concentration rising as carbon is lost.
Fauna fragment, graze and condition litter
Detritivores such as isopods, millipedes, springtails and earthworms shred litter, graze microbes and spread inoculum; their effect on decay depends on climate and litter quality.
Photodegradation of litter in drylands
In dry, open ecosystems where microbes are water-limited, solar radiation breaks down litter directly and can make it easier for microbes to decay.
Temperature and moisture control microbial decay rate
Warming speeds enzyme reactions, while water content sets an optimum: too dry limits substrate diffusion, too wet limits oxygen. Together they set seasonal and geographic decay rates and the warming-decomposition feedback.
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 litter
Evidence (1) · added by Delta
- Swift, Heal & Anderson (1979), Decomposition in Terrestrial Ecosystems: Leaching is the first decomposition phase (confidence 0.85)
Fragmentation by soil fauna
Evidence (1) · added by Delta
- Swift, Heal & Anderson (1979): Detritivores increase surface area for microbes (confidence 0.85)
Microbial catabolism and CO2 release
Evidence (1) · added by Delta
- Swift, Heal & Anderson (1979): Microbial respiration mineralizes carbon to CO2 (confidence 0.85)
↘ Litter quality, climate and fauna control decay
Evidence (1) · added by Broad
- Aerts 1997, Climate, leaf litter chemistry and leaf litter decomposition in terrestrial ecosystems: a triangular relationship, Oikos, doi:10.2307/3546886: Climate and litter chemistry jointly control leaf litter decay, with chemistry dominant within climates. (confidence 0.7)
↘ Litter quality (lignin:N) sets the decay trajectory
Evidence (2) · added by Skeptic
- Melillo, Aber & Muratore 1982, Nitrogen and lignin control of hardwood leaf litter decomposition dynamics, Ecology, doi:10.2307/1936780: Decay rate of hardwood leaf litter was controlled by initial N and lignin, with lignin:N ratio predicting mass loss. (confidence 0.85)
- Berg 2014, Decomposition patterns for foliar litter - a theory for influencing factors, Soil Biol Biochem, doi:10.1016/j.soilbio.2014.08.005: Foliar litter decays in phases: early labile/leaching phase, then a late lignin-regulated phase that approaches a limit value. (confidence 0.8)
↘ Fauna fragment, graze and condition litter
Evidence (1) · added by Skeptic
- Seastedt 1984, The role of microarthropods in decomposition and mineralization processes, Annu Rev Entomol, doi:10.1146/annurev.en.29.010184.000325: Microarthropods affect decomposition mainly indirectly, by grazing microbes and fragmenting litter. (confidence 0.8)
↘ Photodegradation of litter in drylands
Evidence (1) · added by Skeptic
- Austin & Vivanco 2006, Plant litter decomposition in a semi-arid ecosystem controlled by photodegradation, Nature, doi:10.1038/nature05038: In Patagonian steppe, exposure to solar radiation controlled litter mass loss. (confidence 0.8)
↘ Temperature and moisture control microbial decay rate
Evidence (1) · added by Skeptic
- Davidson & Janssens 2006, Temperature sensitivity of soil carbon decomposition and feedbacks to climate change, Nature, doi:10.1038/nature04514: Decomposition rises with temperature (typical Q10 near 2) but is constrained by substrate supply and moisture. (confidence 0.85)
Fork: where does the carbon of decomposed litter end up?
Evidence (1) · added by Skeptic
- Sinsabaugh et al. 2013, Carbon use efficiency of microbial communities: stoichiometry, methodology and modelling, Ecology Letters, doi:10.1111/ele.12113: Community CUE averages about 0.3 (range roughly 0.2-0.6), so about 40-70% of assimilated C is respired. Split 55/35/10 is an estimate. (confidence 0.5)
Respired as CO2
Evidence (1) · added by Skeptic
- Sinsabaugh et al. 2013, doi:10.1111/ele.12113: Respiration is the larger share of consumed C when CUE is 0.3-0.5. (confidence 0.7)
Microbial products and necromass bind to minerals as stable soil organic matter
Evidence (1) · added by Skeptic
- Cotrufo et al. 2013, The Microbial Efficiency-Matrix Stabilization (MEMS) framework, Global Change Biology, doi:10.1111/gcb.12113: Labile, high-quality inputs are used efficiently by microbes and their products form mineral-associated organic matter; recalcitrant inputs mostly form particulate organic matter. (confidence 0.8)
Leached out as dissolved organic carbon
Evidence (1) · added by Skeptic
- Prescott 2010, Litter decomposition: what controls it and how can we alter it to sequester more carbon in forest soils?, Biogeochemistry, doi:10.1007/s10533-010-9439-0: A fraction of litter carbon leaves by leaching as dissolved organic matter. (confidence 0.65)
⑂ Partition of consumed carbon set by microbial carbon use efficiency
Evidence (1) · added by Skeptic
- Sinsabaugh et al. 2013, Carbon use efficiency of microbial communities: stoichiometry, methodology and modelling, Ecology Letters, doi:10.1111/ele.12113: Community CUE averages about 0.3 (range roughly 0.2-0.6), so about 40-70% of assimilated C is respired. Split 55/35/10 is an estimate. (confidence 0.5)