Modeling competition between plants using an Individual Based Model: Methods and effects on the growth of two species with contrasted growth forms

Individual Based Models are emergent modeling approaches that are developed on the behavior of interacting individuals to study ecosystems properties. Their relevance resides in the validity of the interaction rules between individuals defined in the model. Competitive interactions between plant individuals can be implemented from the combination of four main attributes: (i) the zone of interaction of the target plant, (ii) the intensity of competition, (iii) the effect of competition, and (iv) the target plant response. This study aims at determining the effects of the method used for modeling competition on the performance and individual architecture of two species. We simulated the growth of a guerilla and of a phalanx species either in monoculture or in mixture using 61 methods for modeling competition derived from the published literature and implemented in an Individual Based Model. We showed that (i) the performance and individual architecture of the two species varies with the modefling method, (ii) the effect of the modeling method on the model outputs depends on the species and on the assemblage considered. We subsequently emphasized the importance of accurately calibrating models in particular with experimental data. We finally proposed basic rules supported by literature to evaluate the relevance of the different methods tested.