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Earth's Systems / Biological processes / Terrestrial ecosystem functioning / Terrestrial nutrient cycling / Nitrogen and phosphorus supply and limitation

Nitrogen and phosphorus supply and limitation

How soil organic nitrogen is released, how microbes and plants compete for it, and how phosphorus availability declines with soil age and is rescued by plant and microbial strategies.

Boundary: where this process starts

Starts with: Organic nitrogen is depolymerised to amino acids

Boundary: where it ends

Ends after: Microbes immobilise nitrogen in biomass; Phosphorus decline and rescue across soil ages

PARTICIPANTSRESOURCESMicrobesPlantsMycorrhizalfungiSoil faunaNitrogenSoil organicmatterOrganic carbonPhosphorusMineralnutrientsImpact +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.60% microbial uptakeImpact -2 of 5. Click for details and evidence.Impact +3 of 5. Click for details and evidence.Impact 02 of 5. Click for details and evidence.Impact +3 of 5. Click for details and evidence.40% plant uptakeOrganic nitrogen is depolymerised to amino acids: uses up Nitrogenuses upOrganic nitrogen is depolymerised to amino acids: uses up Soil organic matteruses upWho takes up the released inorganic nitrogen: uses up Nitrogenuses upMicrobes immobilise nitrogen in biomass: uses up Nitrogenuses upMicrobes immobilise nitrogen in biomass: uses up Organic carbonuses upPlants take up ammonium and nitrate: uses up Nitrogenuses upPhosphorus decline and rescue across soil ages: uses PhosphorusPhosphorus decline and rescue across soil ages: uses Mineral nutrientsfreed as amino acidsNitrogen: freed as amino acidsdepolymerised by enzymesSoil organic matter: depolymerised by enzymestaken up by plants andmicrobesNitrogen: taken up by plants and microbeslocked into microbialbiomassNitrogen: locked into microbial biomassincorporated intomicrobial cellsOrganic carbon: incorporated into microbial cellsabsorbed by plant rootsNitrogen: absorbed by plant rootsdeclines as soil agesPhosphorus: declines as soil agessupplies shrink withweatheringMineral nutrients: supplies shrink with weatheringStart: Nitrogen andphosphorus supply andlimitationSTARTStart: Nitrogen and phosphorus supply and limitationEnd: Nitrogen andphosphorus supply andlimitationENDEnd: Nitrogen and phosphorus supply and limitationOrganic nitrogen isdepolymerised to aminoacids📄1Organic nitrogen is depolymerised to amino acidsWho takes up thereleased inorganicnitrogen📄1Who takes up the released inorganic nitrogenMicrobes immobilisenitrogen in biomass👍1📄1Microbes immobilise nitrogen in biomassPlants take up ammoniumand nitrate📄1 ↗1Plants take up ammonium and nitratePhosphorus decline andrescue across soil ages↘📄1Phosphorus decline and rescue across soil ages
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.

Inside this process

Phosphorus decline and rescue across soil ages

As soils age primary-mineral phosphorus is depleted and occluded, shifting ecosystems from nitrogen to phosphorus limitation unless plants and microbes mobilise organic and bound phosphorus.

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.

Organic nitrogen is depolymerised to amino acids
MicrobesSoil faunaNitrogenSoil organic matter
Evidence (1) · added by Broad
  • Schimel & Bennett 2004, Nitrogen mineralization: challenges of a changing paradigm, Ecology, doi:10.1890/03-8002: Depolymerisation by extracellular enzymes is the rate-limiting step in N supply. (confidence 0.75)
⑂ Who takes up the released inorganic nitrogen
MicrobesPlantsNitrogen
Evidence (1) · added by Broad
  • Schimel & Bennett 2004, Nitrogen mineralization: challenges of a changing paradigm, Ecology, doi:10.1890/03-8002: Microbes compete well for N in the short term; plants get the remainder. 60/40 is an estimate (range 50-80% microbes). (confidence 0.4)
Microbes immobilise nitrogen in biomass
MicrobesNitrogenOrganic carbon
Evidence (1) · added by Broad
  • Schimel & Bennett 2004, Nitrogen mineralization: challenges of a changing paradigm, Ecology, doi:10.1890/03-8002: Microbes with high C demand immobilise N. (confidence 0.6)
Plants take up ammonium and nitrate
PlantsMycorrhizal fungiNitrogen
Evidence (1) · added by Broad
  • LeBauer & Treseder 2008, Nitrogen limitation of net primary productivity in terrestrial ecosystems is globally distributed, Ecology, doi:10.1890/06-2057.1: N uptake supports production, which responds to N addition across biomes. (confidence 0.65)
↘ Phosphorus decline and rescue across soil ages
PlantsMicrobesMycorrhizal fungiPhosphorusMineral nutrients
Evidence (1) · added by Broad
  • Walker & Syers 1976, The fate of phosphorus during pedogenesis, Geoderma, doi:10.1016/0016-7061(76)90066-5: Walker and Syers model: primary mineral P declines over pedogenesis while occluded and organic P rise. (confidence 0.8)