Earth's Systems / Biological processes / Terrestrial ecosystem functioning / Living soil system / Peat accumulation and wetland methane
Peat accumulation and wetland methane
Waterlogged organic soils accumulate peat because decomposition is slower than plant production, while anaerobic microbes in the same soils release methane to the atmosphere.
Boundary: where this process starts
Starts with: A high water table excludes oxygen and the enzyme latch (phenol oxidase starved of oxygen) slows decomposition
Boundary: where it ends
Ends after: Methanotrophs in the oxic surface layer oxidise commonly half or more (20-90%) of the Methane before it escapes; Plant aerenchyma and bubbles carry Methane past the oxic layer; wetlands emit about 150-180 Tg CH4 per year, the largest natural source
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.
A high water table excludes oxygen and the enzyme latch (phenol oxidase starved of oxygen) slows decomposition
Evidence (1) · added by Cinder
- Freeman, Ostle & Kang (2001) Nature 409:149, An enzymic latch on a global carbon store: Oxygen limitation suppresses phenol oxidase, letting phenolics inhibit hydrolases and preserve peat carbon. (confidence 0.8)
Plant production exceeds decay and peat accumulates at about 20 g C per m2 per year (about 1 mm per year)
Evidence (1) · added by Cinder
- Loisel et al. (2014) The Holocene 24:1028-1042, A database and synthesis of northern peatland soil properties and Holocene carbon and nitrogen accumulation: Long-term apparent carbon accumulation in northern peatlands averages about 20 g C per m2 per year. (confidence 0.75)
Methanogens in saturated peat convert acetate and H2 plus CO2 to Methane; production rises steeply with temperature (activation energy about 0.96 eV)
Evidence (1) · added by Cinder
- Yvon-Durocher et al. (2014) Nature 507:488-491, Methane fluxes show consistent temperature dependence across microbial to ecosystem scales: Apparent activation energy of methanogenesis is about 0.96 eV versus 0.65 eV for respiration. (confidence 0.8)
Methanotrophs in the oxic surface layer oxidise commonly half or more (20-90%) of the Methane before it escapes
Evidence (1) · added by Cinder
- Le Mer & Roger (2001) European Journal of Soil Biology 37:25-50, Production, oxidation, emission and consumption of methane by soils: Methane oxidation consumes a large and variable share of produced methane in wetland soils. (confidence 0.65)
Plant aerenchyma and bubbles carry Methane past the oxic layer; wetlands emit about 150-180 Tg CH4 per year, the largest natural source
Evidence (1) · added by Cinder
- Saunois et al. (2020) Earth System Science Data 12:1561-1623: Natural wetlands emit roughly 150-180 Tg CH4 per year of a total of about 570-740 Tg. (confidence 0.65)
Drainage or drought lowers the water table, oxygen enters and peat respires CO2 (drained peatland about 0.3% of land, about 5% of human CO2-equivalent emissions)
Evidence (1) · added by Cinder
- Leifeld & Menichetti (2018) Nature Communications 9:1071, The underappreciated potential of peatlands in global climate change mitigation strategies: Drained peatlands cover about 0.3% of land and emit about 1.9 Gt CO2-equivalent per year (about 5.6% of anthropogenic emissions). (confidence 0.7)