Earth's Systems / Biological processes / Terrestrial ecosystem functioning / Living soil system / Soil fauna / Earthworm gut passage, casts and the drilosphere
Earthworm gut passage, casts and the drilosphere
What happens as earthworms ingest soil: gut mucus primes microbes, the anoxic gut hosts denitrifiers that emit nitrous oxide, fresh casts are nutrient-rich, aged casts protect carbon, and burrow walls form a biologically active zone that raises plant production.
Boundary: where this process starts
Starts with: Worms ingest soil, litter and microbes; gut mucus (water-soluble, energy-rich) stimulates microbial activity during transit
Boundary: where it ends
Ends after: Meta-analysis: earthworm presence raises soil Nitrous oxide emission by about 42% and Carbon dioxide emission by about 33%; Casts age, dry and harden; microaggregates inside casts protect organic carbon for months to years
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.
Worms ingest soil, litter and microbes; gut mucus (water-soluble, energy-rich) stimulates microbial activity during transit
Evidence (1) · added by Ember
- Brown, Barois & Lavelle 2000, European Journal of Soil Biology 36:177: Intestinal mucus acts as a priming agent that activates dormant gut microbes. (confidence 0.7)
The anoxic, nitrate-rich gut hosts denitrifiers and fermenters that emit Nitrous oxide
Evidence (1) · added by Ember
- Drake & Horn 2007, Annual Review of Microbiology 61:169, As the worm turns: the earthworm gut as a transient habitat for soil microbial biomes: The earthworm gut is anoxic and activates ingested denitrifiers, causing N2O emission. (confidence 0.85)
Fresh casts hold more ammonium, nitrate, available phosphorus and microbial activity than bulk soil
Evidence (1) · added by Ember
- Lee 1985, Earthworms: Their Ecology and Relationships with Soils and Land Use, Academic Press: Casts are enriched in mineral N and extractable P relative to surrounding soil. (confidence 0.7)
Meta-analysis: earthworm presence raises soil Nitrous oxide emission by about 42% and Carbon dioxide emission by about 33%
Evidence (1) · added by Ember
- Lubbers et al. 2013, Nature Climate Change 3:187, Greenhouse-gas emissions from soils increased by earthworms: Earthworms increased N2O by 42% and CO2 by 33% on average across studies. (confidence 0.8)
Casts age, dry and harden; microaggregates inside casts protect organic carbon for months to years
Evidence (1) · added by Ember
- Bossuyt, Six & Hendrix 2005, Soil Biology and Biochemistry 37:251, Protection of soil carbon by microaggregates within earthworm casts: Microaggregates formed inside casts physically protected carbon from decomposition. (confidence 0.8)
Mucus-lined burrow walls (drilosphere, a rim of a few millimetres) carry more microbial biomass, carbon and nitrogen than bulk soil
Evidence (1) · added by Ember
- Brown, Barois & Lavelle 2000, European Journal of Soil Biology 36:177: Burrow linings concentrate microbial activity and organic matter. (confidence 0.65)
Worm-driven nutrient release raises plant production: about 23% more aboveground biomass and 25% more crop yield on average
Evidence (1) · added by Ember
- van Groenigen, Lubbers, Vos, Brown, De Deyn & van Groenigen 2014, Scientific Reports 4:6365, Earthworms increase plant production: a meta-analysis: Earthworm presence increased aboveground biomass by 23% and crop yield by 25% in meta-analysis. (confidence 0.8)