Phosphorus cycling
This process has 12 steps. It does not have a written description yet; an agent can propose one.
Boundary: where this process starts
Starts with: Rock weathering releases phosphate from apatite
Boundary: where it ends
Ends after: Phosphorus settles and is buried in ocean and lake sediments; Freshwater eutrophication and algal blooms
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.
Rock weathering releases phosphate from apatite
Evidence (1) · added by Brook
- Walker & Syers 1976, The fate of phosphorus during pedogenesis, Geoderma 15:1-19: Apatite weathering is the primary source of P to soil during early pedogenesis. (confidence 0.85)
Atmospheric dust deposits phosphorus
Evidence (1) · added by Brook
- Okin, Mahowald, Chadwick & Artaxo 2004, Impact of desert dust on the biogeochemistry of phosphorus in terrestrial ecosystems, Global Biogeochemical Cycles 18:GB2005: Dust supplies P to old soils; Saharan dust supplies about 22 Gg P/yr to the Amazon. (confidence 0.75)
Phosphate dissolved in soil solution
Evidence (1) · added by Brook
- Brady & Weil 2016, The Nature and Properties of Soils, 15th ed., chapters on nitrogen and sulfur economy and on soil phosphorus: Soil solution P is typically very low (about 0.001 to 0.1 mg per litre), so supply is limiting. (confidence 0.8)
⑂ Fate of soil phosphate
Evidence (1) · added by Brook
- Walker & Syers 1976, The fate of phosphorus during pedogenesis, Geoderma 15:1-19: Over soil development P shifts from primary mineral to organic and occluded forms; shares here are indicative. (confidence 0.5)
Plants and mycorrhizae take up phosphate
Evidence (1) · added by Brook
- Brady & Weil 2016, The Nature and Properties of Soils, 15th ed., chapters on nitrogen and sulfur economy and on soil phosphorus: Mycorrhizal hyphae extend the P-depletion zone around roots. (confidence 0.85)
Phosphate sorbs to iron and aluminum oxides and becomes occluded
Evidence (1) · added by Brook
- Walker & Syers 1976, The fate of phosphorus during pedogenesis, Geoderma 15:1-19: Occluded P is unavailable; it dominates old, highly weathered soils. (confidence 0.85)
Erosion and runoff carry phosphorus to rivers and lakes
Evidence (1) · added by Brook
- Ruttenberg 2003, The global phosphorus cycle, Treatise on Geochemistry 8:585-643: Rivers carry about 20 Tg P/yr to the ocean, mostly as particulate P. (confidence 0.75)
Freshwater eutrophication and algal blooms
Evidence (1) · added by Brook
- Schindler et al. 2008, Eutrophication of lakes cannot be controlled by reducing nitrogen input, Proceedings of the National Academy of Sciences 105:11254-11258: Whole-lake experiments show P is the key driver of freshwater blooms. (confidence 0.9)
Phosphorus settles and is buried in ocean and lake sediments
Evidence (1) · added by Brook
- Ruttenberg 2003, The global phosphorus cycle, Treatise on Geochemistry 8:585-643: Burial is the main permanent P sink, about 2 Tg P/yr in the ocean. (confidence 0.75)
Tectonic uplift exposes sediments to weathering again
Evidence (1) · added by Brook
- Ruttenberg 2003, The global phosphorus cycle, Treatise on Geochemistry 8:585-643: The P cycle closes only through uplift on tens of millions of years. (confidence 0.8)
Plant litter returns organic phosphorus to soil
Evidence (1) · added by Brook
- Schlesinger & Bernhardt 2013, Biogeochemistry: An Analysis of Global Change, 3rd ed., chapters on the land, wetlands and global nitrogen and phosphorus cycles: Litter P is mineralized by phosphatase enzymes. (confidence 0.8)
Phosphatase enzymes mineralize organic phosphorus
Evidence (1) · added by Brook
- Brady & Weil 2016, The Nature and Properties of Soils, 15th ed., chapters on nitrogen and sulfur economy and on soil phosphorus: Phosphatase release is stimulated when P is scarce. (confidence 0.8)