Asymmetric light competition and founder control in plant communities

We explore the effects of asymmetric competition for light on the outcome of interspecific competition in simple models of resource competition. The models assume that species only differ in their allocation of resource to roots and photosynthetic tissues. Previous studies, which assume symmetric competition for light, have found that all two-species equilibria are unstable leading to founder control, and that as species become more similar in their allocation of resources to roots and photosynthetic tissues so the likelihood of founder control is reduced. In contrast when competition for light is asymmetric as species become more similar the likelihood of founder control increases. Vegetative successions in the model can proceed in one of two directions - from nutrient specialist, with a high allocation to roots, to light specialists, with low allocation to roots, or vice versa. Low nutrient, low disturbance habitats tend to have successions running from light specialists to nutrient specialists, whereas high nutrient, high disturbance habitats have successions in the opposite direction. When light competition is symmetric, we demonstrate that only successions from leaf specialists to root specialists can become arrested. In contrast, when light competition is asymmetric either type of succession may be arrested. Hence, asymmetric competition can have important effects on the outcome of inter-specific competition and on ecosystem properties.