- Liebig's law of the minimum. Liebig's (1840) experiments to test the effects of fertilizers on agricultural production demonstrated that the nutrient in shortest supply was the one that limited yields.
- Law of limiting factors. A restatement of Liebig's law by Blackman (1905).
- Keystone predators. Paine (1980) showed by predator manipulation experiments in littoral communities that certain "keystone" predators had a dominating effect on the dynamics of all the species in the community. This idea lead to the concept that community dynamics was dominated by a few strong interactions (Paine 1992).
- Food web simplification. Theoretical studies by Michalski and Arditi (1995) on complex food webs suggest that many (or most) of the potential interactions in complex ecosystems are lost (become effectively zero) as the system evolves towards equilibrium, so that the dynamics become dominated by a few strong interactions or dominant feedbacks (see figure).
- Limiting guilds. A limiting factor may consist of a group, or "guild" of similar or coacting single factors. For example, aphids can be limited by a group of insect predators (Morris 1992).
- Limiting hierarchies. Groups of factors may act in a hierarchical manner to regulate population density. For example, many forest insects are regulated by generalist predators at very sparse densities, by more highly specialized insect parasitoids if they escape from generalists, by viruses or other pathogens if they escape from the specialist parasitoids, and by starvation if all else fails to control them (Berryman et al. 1987).
- Berryman, A. A., N. C. Stenseth and A. S. Isaev. 1987. Natural regulation of herbivorous forest insect populations. Oecologia 71: 174-184.
- Blackman, F. F. 1905. Optima and limiting factors. Annals of Botany 19: 281-295.
- Liebig, J. 1840. Chemistry and its application to agriculture and physiology. Taylor and Walton, London.
- Michalski, J and R. Arditi. 1994. Food web structure at equilibrium and far from it: is it the same? Proceedings of the Royal Society of London B, 259: 217-222.
- Paine, R. T. 1980. Food webs: linkage, interaction strength and community infrastructure. Journal of Animal Ecology 49: 667-685.
- Paine, R. T. 1992. Food-web analysis through field measurement of per-capita interaction strength. Nature 355: 73-75.
- Morris, W. F. 1992. The effects of natural enemies, competition, and host plant water availability on an aphid population, Oecologia 90: 359-365.
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