Changes in the environment

Although certain feedbacks may dominate the dynamics of a population over a particular period of time and in a particular place, dominance can shift from one feedback mechanism to another depending on environmental conditions. For example, adding nitrogen fertilizer may alleviate competition for nitrogen but some other nutrient like phosphorus would soon become limiting.

Density induced changes

Feedback dominance can also shift in response to changes in the density of the population. For example, when populations are very dense, the hazards of living in a crowd should be greater than the rewards, and so intraspecific competition should dominate. On the other hand, when density is very low, the benefits of communal living should outweigh the hazards of competition, and intraspecific cooperation should dominate. Under these conditions, the R-function can have a positive slope at low densities and negative slope at high densities (see figure).

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