RECOLONIZATION OF CLEARED PATCHES BY MACROPHYTES - MODELING WITH POINT-PROCESSES AND RANDOM MOSAICS

The maintenance of the aquatic vegetation mosaic in a former channel o f the Rhone River frequently disturbed by floods was experimentally in vestigated by clearing patches of the mosaic and by studying the recol onization processes. The present paper proposes a simulation of the ea rly stages of recolonization and a comparison of the results of the mo delling process with data obtained from the field experiment. The hypo theses 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 o nce it was established. The proposed model was based on spatial point processes and random mosaics: the initial germs were dispersed over th e plan using a Poisson point process, and a generator of spatial patte rns, the stochastic pyramid, was used to make these germs grow. The mo del appears useful in predicting the occupation of space by the specie s if their colonization mechanisms are known. It should be helpful in predicting colonization patterns by considering several species that s imultaneously grow and compete on the same patch. (C) 1997 Elsevier Sc ience B.V.