EXPERIMENTAL DISCRIMINATION BETWEEN CONTRASTING MODELS OF NEIGHBORHOOD COMPETITION

1. Previously published competition models have been categorized into four types, based on the territorial extent over which individual plants are assumed to draw resources. 2. The different types of models give different expectations for the growth responses of focal plants when the spacing of neighbours is systematically varied, thus allowing the different types of model to be discriminated. 3. These systematic spacings were imposed in three experiments using carrots (Daucus carota L). The absolute growth rate (AGR) of single plants located at the centre of a ring of four plants was less than that of such plants encompassed by three rings of plants. The difference in AGR between these two treatments initially increased but then became constant. 4. These findings support the 'overlapping domain' type of model and are shown to falsify the assumptions made by other types of competition model. 5. Experiments in which the spacing of individual plants were systematically varied in contrasting light and nutrient regimes did not support the expectation that a 'non-overlapping domain' type of model would be most appropriate to simulate the competitive interactions between plants when light is the resource subject to competition.