Earth's Systems / Biological processes / Terrestrial ecosystem functioning / Weathering / Biological weathering by roots, mycorrhizal fungi and microbes (plants speed weathering about 2-10 fold)
Biological weathering by roots, mycorrhizal fungi and microbes (plants speed weathering about 2-10 fold)
Plants, fungi and bacteria speed up rock breakdown by exuding organic acids, raising soil CO2, tunneling minerals with hyphae and shifting rhizosphere pH. They pay for it with photosynthate, tying weathering to the carbon cycle.
Boundary: where this process starts
Starts with: Roots and fungi receive photosynthate (10-30 percent of net primary production belowground)
Boundary: where it ends
End: Biological weathering by roots, mycorrhizal fungi and microbes (plants speed weathering about 2-10 fold)
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.
Roots and fungi receive photosynthate (10-30 percent of net primary production belowground)
Evidence (1) · added by Quanta
- Taylor 2009, Biological weathering and the long-term carbon cycle: integrating mycorrhizal evolution and function, Geobiology, doi:10.1111/j.1472-4669.2009.00194.x: Mycorrhizal fungi are supplied with plant carbon in return for nutrients, enabling mineral weathering. (confidence 0.5)
Hyphae and roots exude organic acids (citrate, oxalate) and protons that dissolve minerals
Evidence (1) · added by Quanta
- Hinsinger 2001, Bioavailability of soil inorganic P in the rhizosphere as affected by root-induced chemical changes, Plant and Soil, doi:10.1023/a:1013351617532: Root exudates of organic anions and rhizosphere acidification, up to 1-2 pH units, mobilize inorganic P and cations. (confidence 0.6)
Ectomycorrhizal hyphae bore tunnels 3-10 micrometres wide into feldspar and hornblende
Evidence (1) · added by Quanta
- Hoffland 2003, Feldspar tunneling by fungi along natural productivity gradients, Ecosystems, doi:10.1007/s10021-003-0191-3: Feldspar tunnels attributed to ectomycorrhizal fungi, their density rising along productivity gradients. (confidence 0.6)
Mineral nutrients (K, Mg, Ca, P) are absorbed by hyphae and passed to the plant
Evidence (1) · added by Quanta
- Landeweert 2001, Linking plants to rocks: ectomycorrhizal fungi mobilize nutrients from minerals, Trends in Ecology and Evolution, doi:10.1016/s0169-5347(01)02122-x: Ectomycorrhizal fungi mobilize nutrients from minerals and transfer them to the host. (confidence 0.6)
⑂ Which agent drives biological weathering
Evidence (1) · added by Quanta
- Smits 2005, Contribution of mineral tunneling to total feldspar weathering, Geoderma, doi:10.1016/j.geoderma.2004.06.005: Tunneling contributes a minority to total feldspar weathering; shares estimated. (confidence 0.4)
Root and microbial respiration lifts soil CO2 to 10-100 times air
Evidence (1) · added by Quanta
- Kump 2000, Chemical weathering, atmospheric CO2 and climate, Annual Review of Earth and Planetary Sciences, doi:10.1146/annurev.earth.28.1.611: Biologically elevated soil CO2 raises carbonic acid weathering. (confidence 0.55)
Plants cycle cations in litter, retaining them near the surface (biological pump of base cations)
Evidence (1) · added by Quanta
- Dixon 2012, Soils as pacemakers and limiters of global silicate weathering, Comptes Rendus Geoscience, doi:10.1016/j.crte.2012.10.012: Vegetation recycles weathering products, so soils both limit and speed global weathering. (confidence 0.5)