Seed bank assembly follows vegetation succession in dune slacks

Abstract

Question: Is the seed bank in dune slacks during the whole successional range mainly composed of early successional species or does it vary according to the changing vegetation? Location: Belgium, western part of the coast. Methods: We investigated the soil seed bank composition using a seedling germination method in a chronosequence of 20 dune slacks, ranging in age from five to 55 yr. Results: Both seed density and species richness in the seed bank were very low in the first successional stages and increased with age, mainly as a result of increasing seed production. The similarity between seed bank and vegetation was higher in older slacks. A comparison of characteristics between seed bank and vegetation showed that the seed bank was, to a large extent, composed of later successional species. Occurrence patterns of individual species also showed that seeds become incorporated in the soil after the species has established in the vegetation. Conclusion: The seed bank is not likely to be the driving force for successional changes in the vegetation, and successional changes rely on dispersal. Some early successional species persist in the seed bank, but generally only in low numbers. The results also confirm that most typical dune slack species do not form persistent seeds, so that re-establishment from the seed bank is not to be expected when the species has disappeared from the vegetation.