THE DEVELOPMENT OF SIZE STRUCTURE IN A YOUNG FUCUS-SERRATUS POPULATION

Artificial discs were used to monitor the settlement and development o f Fucus serratus propagules in five areas cleared of an adult canopy, in order to test the assumptions that sizes of recently settled propag ules are normally distributed but that over time plant sizes become mo re variable and hierarchical. Settlement was spatially (3-20 m) variab le only at the beginning and end of the settlement period, and at the time when most settlement took place (88% in a fortnight) no differenc es between areas were found. Increases in the skewness coefficient, Gi ni coefficient and coefficient of variation confirmed that there was n ot a size hierarchy in the recently settled population, but 8 months l ater sizes of plants were variable and a positive skew in plant sizes (many small and few big) developed. Mortality was high at first (70% i n 1 month) but fell considerably later. F. serratus behaves like most higher plants with respect to changing population structure. The obser ved change in population structure provided evidence of how a ''seed b ank'' develops in an algal population, as 1 year after settlement an e stimated 37 000 plants m(-1) are still <1 mm in length.