Recolonization of cleared patches by macrophytes: Modelling with point processes and random mosaics

The maintenance of the aquatic vegetation mosaic in a former channel of the Rhône River frequently disturbed by floods was experimentally investigated by clearing patches of the mosaic and by studying the recolonization processes. The present paper proposes a simulation of the early stages of recolonization and a comparison of the results of the modelling process with data obtained from the field experiment. The hypotheses were that one macrophyte species could colonize patches (1) by border effect from the adjacent vegetation, (2) totally at random or (3) through an intermediate pattern, and that its abundance increased once it was established. The proposed model was based on spatial point processes and random mosaics: the initial germs were dispersed over the plan using a Poisson point process, and a generator of spatial patterns, the stochastic pyramid, was used to make these germs grow. The model appears useful in predicting the occupation of space by the species if their colonization mechanisms are known. It should be helpful in predicting colonization patterns by considering several species that simultaneously grow and compete on the same patch.