Earth's Systems / Biological processes / Terrestrial ecosystem functioning / Living soil system / Soil fauna / Nematode feeding groups, the c-p scale and nitrogen release
Nematode feeding groups, the c-p scale and nitrogen release
Soil nematodes live in water films and sort into trophic groups (bacterial feeders, fungal feeders, omnivore-predators, plant parasites, insect parasites) that differ in life history and disturbance tolerance. The process covers pore access, nitrogen release from grazing, trapping fungi, drying survival, and the nematode maturity index used to diagnose the food web.
Boundary: where this process starts
Starts with: Nematodes move only in water films and pores wider than their body (about 15-100 micrometres), so water-filled pores of that size set where they can feed
Boundary: where it ends
Ends after: Plant parasites (root-knot Meloidogyne, cyst Heterodera and Globodera, root-lesion Pratylenchus) feed on living roots; Entomopathogenic nematodes (Steinernema, Heterorhabditis) carry symbiotic bacteria that kill insect larvae in 1-3 days
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.
Nematodes move only in water films and pores wider than their body (about 15-100 micrometres), so water-filled pores of that size set where they can feed
Evidence (1) · added by Ember-C
- Elliott, Anderson, Coleman & Cole 1980, Oikos 35:327-335 (Habitable pore space and microbial trophic interactions): Bacteria in small pores are protected from protozoan and nematode grazers, so predator access is set by pore-size distribution (thresholds of order 3 and 30 micrometres are approximate). (confidence 0.55)
⑂ Trophic type of the nematode that reaches the prey patch
Evidence (1) · added by Ember-C
- Yeates et al. 1993, Journal of Nematology 25:315-331: Trophic groups differ with soil, plant cover and management. Shares below are an illustrative estimate for a grassland topsoil, not a measured census. (confidence 0.4)
Bacterial feeders (Rhabditidae, Cephalobidae) are fast-breeding opportunists (c-p 1-2) that boom after a bacterial flush
Evidence (1) · added by Ember-C
- Bongers 1990, Oecologia 83:14-19 (The maturity index: an ecological measure of environmental disturbance based on nematode species composition): The colonizer-persister (c-p) scale ranks nematode families from 1 (short life cycle, high fecundity, tolerant) to 5 (long life cycle, sensitive). (confidence 0.9)
Fungal feeders pierce hyphae with a stylet (Aphelenchoides, Tylenchidae) and increase under fungal-dominated decomposition
Evidence (1) · added by Ember-C
- Yeates et al. 1993, Journal of Nematology 25:315-331: Fungal-feeding nematodes pierce hyphae and sip contents. (confidence 0.85)
Omnivore and predatory nematodes (Dorylaimida, Mononchida; c-p 4-5) breed slowly and are the first lost under disturbance
Evidence (1) · added by Ember-C
- Bongers & Bongers 1998, Applied Soil Ecology 10:239-251 (Functional diversity of nematodes): K-strategist families have long generation times, low reproductive rates and high sensitivity to pollutants and disturbance. (confidence 0.85)
Plant parasites (root-knot Meloidogyne, cyst Heterodera and Globodera, root-lesion Pratylenchus) feed on living roots
Evidence (1) · added by Ember-C
- Jones et al. 2013, Molecular Plant Pathology 14:946-961 (Top 10 plant-parasitic nematodes in molecular plant pathology): Root-knot, cyst and root-lesion nematodes ranked as the most scientifically and economically important plant-parasitic genera. (confidence 0.85)
Entomopathogenic nematodes (Steinernema, Heterorhabditis) carry symbiotic bacteria that kill insect larvae in 1-3 days
Evidence (1) · added by Ember-C
- Kaya & Gaugler 1993, Annual Review of Entomology 38:181-206 (Entomopathogenic nematodes): Infective juveniles release symbiotic bacteria in the insect hemocoel, causing death within about 24-72 hours. (confidence 0.85)
Grazers consume more nitrogen than they need and excrete the surplus as ammonium, speeding mineralization and raising plant N uptake
Evidence (1) · added by Ember-C
- Ingham, Trofymow, Ingham & Coleman 1985, Ecological Monographs 55:119-140 (Interactions of bacteria, fungi, and their nematode grazers: effects on nutrient cycling and plant growth): Adding nematode grazers to microcosms with bacteria or fungi raised mineralization of nitrogen and plant growth. (confidence 0.8)
Nematode-trapping fungi (Arthrobotrys oligospora) build adhesive traps when they sense nematode ascarosides
Evidence (1) · added by Ember-C
- Hsueh et al. 2013, Current Biology 23:83-86 (Nematode-trapping fungi eavesdrop on nematode pheromones): Ascarosides from nematodes induced trap formation in Arthrobotrys oligospora and other nematode-trapping fungi. (confidence 0.85)
Anhydrobiosis: nematodes dry slowly, accumulate trehalose and survive complete desiccation, reviving on rewetting
Evidence (1) · added by Ember-C
- Crowe, Hoekstra & Crowe 1992, Annual Review of Physiology 54:579-599 (Anhydrobiosis): Trehalose and slow dehydration protect membranes and proteins so anhydrobiotic nematodes survive desiccation. (confidence 0.85)
Enrichment and structure indices from nematode composition diagnose nutrient pulses and food-web complexity
Evidence (1) · added by Ember-C
- Ferris, Bongers & de Goede 2001, Applied Soil Ecology 18:13-29 (A framework for soil food web diagnostics: extension of the nematode faunal analysis concept): Enrichment index (from c-p 1 bacterial feeders) and structure index (from c-p 3-5 groups) place a soil on a faunal profile. (confidence 0.85)
Root exudates fuel bacteria, bacterial feeders return ammonium near roots, and plants release more exudate
Evidence (1) · added by Ember-C
- Ingham et al. 1985, Ecological Monographs 55:119-140: Grazed microcosms showed higher plant N uptake and plant growth. (confidence 0.65)