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Earth's Systems / Biological processes / Terrestrial ecosystem functioning / Living soil system / Mineral weathering and parent material / Soil CO2 and biotic enhancement of weathering

Soil CO2 and biotic enhancement of weathering

How roots, mycorrhizal fungi and microbes raise soil carbon dioxide and release organic acids that speed mineral dissolution and nutrient release from rock.

Boundary: where this process starts

Starts with: Root and microbial respiration raise soil CO2 to roughly 10-100 times atmospheric

Boundary: where it ends

Ends after: Plant uptake removes released cations, keeping solution undersaturated

PARTICIPANTSRESOURCESPlant rootsMycorrhizalfungiSoil microbesSoil waterFungiOrganic acidsPotassiumCarbon dioxideSoil organicmatterCarbonic acidImpact +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.Impact +3 of 5. Click for details and evidence.Impact +3 of 5. Click for details and evidence.↻ reinforces · moderate · 0.2 More released Root and microbial respiration raise soil CO2 to roughly 10-100 times atmospheric: makes Carbon dioxidemakesRoot and microbial respiration raise soil CO2 to roughly 10-100 times atmospheric: uses up Soil organic matteruses upCarbonic and organic acids acidify microsites at mineral surfaces: uses Organic acidsCarbonic and organic acids acidify microsites at mineral surfaces: uses Carbonic acidMycorrhizal hyphae tunnel into mineral grains and extract Ca, Mg, K, P: uses Organic acidsMycorrhizal hyphae tunnel into mineral grains and extract Ca, Mg, K, P: uses up Potassiumuses upPlant uptake removes released cations, keeping solution undersaturated: uses up Potassiumuses upreleased by respirationCarbon dioxide: released by respirationrespired by microbes androotsSoil organic matter: respired by microbes and rootsacidify micrositesurfacesOrganic acids: acidify microsite surfacesacidifies mineralmicrositesCarbonic acid: acidifies mineral micrositesdissolve grain surfacesOrganic acids: dissolve grain surfacesextracted from mineralgrainsPotassium: extracted from mineral grainsremoved from solutionPotassium: removed from solutionStart: Soil CO2 andbiotic enhancement ofweatheringSTARTStart: Soil CO2 and biotic enhancement of weatheringEnd: Soil CO2 andbiotic enhancement ofweatheringENDEnd: Soil CO2 and biotic enhancement of weatheringRoot and microbialrespiration raise soilCO2 to roughly 10-1…📄1Root and microbial respiration raise soil CO2 to roughly 10-100 times atmosphericCarbonic and organicacids acidifymicrosites at miner…📄1Carbonic and organic acids acidify microsites at mineral surfacesMycorrhizal hyphaetunnel into mineralgrains and extract C…👍1📄1Mycorrhizal hyphae tunnel into mineral grains and extract Ca, Mg, K, PPlant uptake removesreleased cations,keeping soluti…📄1Plant uptake removes released cations, keeping solution undersaturated
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.

Root and microbial respiration raise soil CO2 to roughly 10-100 times atmospheric
Plant rootsSoil microbesCarbon dioxideSoil organic matter
Evidence (1) · added by Cinder
  • Brook, Folkoff & Box 1983, Earth Surf Process Landforms 8:79: World model of soil CO2: soil air CO2 far above the atmosphere, rising with productivity (confidence 0.7)
Carbonic and organic acids acidify microsites at mineral surfaces
Soil waterPlant rootsFungiCarbonic acidOrganic acidsHydrogen ions
Evidence (1) · added by Cinder
  • Berner, Lasaga & Garrels 1983, Am J Sci 283:641: High soil pCO2 accelerates acid attack (confidence 0.7)
Mycorrhizal hyphae tunnel into mineral grains and extract Ca, Mg, K, P
Mycorrhizal fungiPrimary mineralsOrganic acidsPotassiumPhosphorus
Evidence (1) · added by Cinder
  • Jongmans et al. 1997, Nature 389:682: Narrow hyphal tunnels (3-10 um) in weatherable minerals of forest podzols (confidence 0.8)
Plant uptake removes released cations, keeping solution undersaturated
Plant rootsCalciumMagnesiumPotassium
Evidence (1) · added by Cinder
  • Drever 1994, Geochim Cosmochim Acta 58:2325: Uptake and exudates lower product concentrations, speeding dissolution (confidence 0.65)