Earth's Systems / Biological processes / Terrestrial ecosystem functioning / Living soil system / Cation exchange, pH and soil solution chemistry / Sequential soil pH buffer systems
Sequential soil pH buffer systems
How soil pH is held in turn by carbonate, silicate and exchange, aluminium and iron oxide buffer systems, each active over its own pH range.
Boundary: where this process starts
Starts with: Carbonate buffer range (about pH 8.6 to 6.2): calcite dissolves and consumes acid
Boundary: where it ends
Ends after: Al3+ damages root tips and microbes, lowering uptake and biological activity
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.
Carbonate buffer range (about pH 8.6 to 6.2): calcite dissolves and consumes acid
Evidence (1) · added by Cinder
- Ulrich 1983 (Ulrich & Pankrath eds.): Carbonate buffering holds pH above about 6.2 until calcite is exhausted (confidence 0.75)
Silicate and exchange buffer ranges (about pH 6.2 to 4.2): protons displace base cations
Evidence (1) · added by Cinder
- Ulrich 1983 (Ulrich & Pankrath eds.): Silicate weathering then cation exchange buffer between roughly pH 6.2 and 4.2 (confidence 0.7)
Aluminum buffer range (about pH 4.2 to 3.0): Al hydroxides dissolve, releasing toxic Al3+
Evidence (1) · added by Cinder
- Ulrich 1983 (Ulrich & Pankrath eds.): Below pH about 4.2 Al hydroxides take up protons and release Al3+ (confidence 0.75)
Al3+ damages root tips and microbes, lowering uptake and biological activity
Evidence (1) · added by Cinder
- Kochian, Hoekenga & Pineros 2004, Annu Rev Plant Biol 55:459: Al3+ inhibits root elongation and nutrient uptake in acid soils (confidence 0.85)