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Resource: used or used up in processesNitrogen
Appears in 86 processs and 248 steps. Everything below is linked: open a process to see it in context.
Top processes
Living soil system
11 steps- Nutrient availability and leaching
- Mycorrhizal fungi network
- Saprotrophic fungi
- and 8 more in this process
Terrestrial nutrient cycling
8 steps- Plant nutrient uptake
- Litterfall returns nutrients to soil
- Mineralization and immobilization by microbes
- and 5 more in this process
Soil fauna
8 stepsSaprotrophic fungi
7 stepsNitrogen cycling
7 stepsShow 80 more processes
Roots and rhizosphere
6 stepsMycorrhizal fungi network
6 stepsOrganic matter decomposition
6 stepsBacteria and archaea
5 stepsNutrient cycling
5 steps- Free-living heterotrophic fixers add only about 1-5 kg N per ha per year in most ecosystems
- Legume symbioses supply tens to over 100 kg N per ha per year; agricultural fixation totals about 50-70 Tg N per year
- Nodule senescence, root turnover and rhizodeposition return fixed nitrogen to soil (below-ground N is about 4-70% of legume plant N across studies)
- and 1 more in this process
- Reaching a nutrient-rich patch triggers hyphal proliferation there and thickening of cords back to the base
- Cords and rhizomorphs translocate carbon, nitrogen and phosphorus over decimetres to metres, driven by source-sink gradients
- Fungi import soil nitrogen into N-poor surface litter and speed its decomposition (fungal translocation in no-till residue)
- and 1 more in this process
- Ectomycorrhizal fungi (Cortinarius, Russula, Suillus) secrete peroxidases and proteases that mine organic nitrogen from soil organic matter
- Fungi retain much of the mined nitrogen and pass only part to the tree when fungal N demand is high, aggravating tree N limitation
- Ectomycorrhizal fungi compete with free-living decomposers for N and may slow decomposition (the Gadgil effect): trenching to remove ectomycorrhizal roots raised litter mass loss in a pine plantation
- and 1 more in this process
Primary production
3 steps- Autoregulation of nodulation: shoot-acting CLE peptides and the SUNN/HAR1 receptor kinase cap nodule number
- Rhizobia are released into plant cells and differentiate into nitrogen-fixing bacteroids (in Medicago via NCR peptides, with genome endoreduplication)
- Host sanctions: nodules that fix less nitrogen get less oxygen and their rhizobia reproduce about 50% less
- Bacterivorous nematodes excrete ammonium because bacteria are N-rich prey; nematodes account for roughly 5-20% of net N mineralization (wide range)
- Plant-parasitic nematodes (root-knot Meloidogyne, cyst Heterodera and Globodera) feed on roots; root-knot nematodes induce giant cells that act as nutrient sinks
- Disturbance reshapes the nematode community: tillage and fertilizer favour c-p 1 enrichment opportunists, while undisturbed soils keep c-p 4-5 taxa
Decomposition
3 stepsOften found with
Carbon 86Phosphorus 65Plants 60Ammonium 32Soil microbes 30Soil organic matter 25Water 24Plant roots 21Mycorrhizal fungi 18Decomposers 16Carbon dioxide 16Microbes 15
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