A resource-driven strategy conflict in two dimensions

The behaviour of a model of plant strategies, developed by Colasanti & Grime (1993,Funct. Ecol.7,169–176), is explored in detail both by systematic simulation experiments and by considering theoretical and mathematical aspects. The model considers the three primary strategies for resource capture and utilization described by Grime (1977,Am. Nat.111,1169–1194): ruderals, competitors and stress-tolerators. Each one is represented by a deterministic rule for both its maintenance and seeding while the recycling of resources occurs randomly. These processes take place on a lattice so that the whole model is a probabilistic cellular automaton. A key feature of the model is shown to be the difference between the resource recycling rates of the different species, which is fundamental to explaining the qualitative behaviour of the model. It is shown that the implementation by Colasanti & Grime of the stress-tolerator strategy does not involve resource storage, and therefore that storage is not relevant to explaining the qualitative results they obtain. A variant of the model which illustrates this point is discussed briefly.