The Importance of Competition

Is competition more likely to occur in resource-rich or resource-poor environments?

It is generally agreed that in resource-rich environments, plants are less likely to compete for nutrients because they will not be limiting, but that plants still compete for light because more individuals will survive and develop leaves that reduce available light (Goldberg, 1990). The discussion on whether plants compete in resource-poor environments has been more polarized. Grime (1979) maintains that competition is not important in resource-poor environ ments because resources cannot be depleted further. He argues that plants adapted for stress tolerance will dominate in these environments, while competitors will be favoured in resource-rich environments. Tilman (1988, 1990) argues that competition occurs in resource-poor environments because, while some plants do adapt generally to tolerate these stressful environments, many individuals also deplete resources more than others by having a high efficiency of nutrient uptake. Grace (1990) believes that both theories are compatible and reflect different aspects of competition, i.e. Grime focuses on the long-term competitive effect on a community, while Tilman focuses on the shorter-term competitive response of individuals. Furthermore, if the ability to tolerate being denied resources is considered a competitive trait (Aarssen, 1989, 1992), then stress tolerance is actually a competitive trait. Indeed, most plants do compete in response to resource-poor envi-

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