VEGETATIVE REGENERATION OF FUCUS ROCKWEED CANOPY AS A MECHANISM OF SECONDARY SUCCESSION ON AN EXPOSED ROCKY SHORE

Canopy regeneration by vegetative regrowth from damaged holdfasts has been examined in two species of rockweed, Fucus vesiculosus and Fucus evanescens. About 20-30% of experimentally damaged holdfasts sprouted large numbers of adventitious shoots, even when the basal tissue had been cut to less than 2 mm thickness. Vegetative regrowth was observed from minute amounts of holdfast tissue. This vegetative sprouting appears more important in the F. vesiculosus zone than in the F. evanescens zone. Comparison of Fucus growth in plots with sterilized or damaged holdfasts provided estimates of the relative importance of recruitment and vegetative regrowth to canopy recovery. We consider that vegetative regrowth from basal tissues may make variable but important contributions to succession in this community, and to the persistence of rockweed populations. We argue that the possibility of vegetative regrowth must be considered in interpreting successional patterns, particularly those which followed a recent, severe ice-scour of exposed seashores near Halifax, Nova Scotia.