Infodoc : Sciences, Techniques et Culture

Recent changes in forestry practices raise new scientific issues concerning the dynamics of mixed forests, and especially the coexistence of different species. The spatial structure of such forest stands is known to play a key role in their dynamics, but classical forest models are not adapted to study this phenomenon. Foresters have therefore begun to build distance-dependent individual-based forest models. As far as theoretical models are concerned, the relation between competition and the coexistence of various plant species in a mixed community has been studied extensively in theoretical ecology, but few of the corresponding models explicitly take the spatial structure of the community into account. The aim of this paper is to present a simple individual-based mechanistic model of[...]

Recent changes in forestry practices raise new scientific issues concerning the dynamics of mixed forests, and especially the coexistence of different species. The spatial structure of such forest stands is known to play a key role in their dynamics, but classical forest models are not adapted to study this phenomenon. Foresters have therefore begun to build distance-dependent individual-based forest models. As far as theoretical models are concerned, the relation between competition and the coexistence of various plant species in a mixed community has been studied extensively in theoretical ecology, but few of the corresponding models explicitly take the spatial structure of the community into account. The aim of this paper is to present a simple individual-based mechanistic model of neighbourhood competition that allows to study the relation between the spatial structure of mixed stands and the survival of an inferior competitor. We have build this model as an extension of former theoretical models of competition for a soil resource, by adding explicit spatial interactions. We have studied it both analytically and through simulations, using generalised Gibbs processes to simulate stands of various spatial structures. At the individual scale, we have obtained an explicit relation between the survival of a tree, the specific composition of its neighbourhood, and soil fertility. At the stand scale, we have linked the number of surviving trees to the spatial structure, and shown how interspecific repulsion and aggregated patterns improve the survival of inferior competitors. We have also illustrated how the competition process modifies the spatial structure of the stand. Such a neighbourhood competition model is thus a useful tool to study the relation between the spatial structure of a community and its dynamics.