Seed mass, shape, and persistence in the soil seed bank of Israeli coastal sand dune flora

Question: Are seed mass and shape related to persistence in the soil seed bank among 54 species of the Israeli flora? Search method: Persistence was determined by soil seed bank investigations in which the fraction of non-germinated viable seeds was regarded as the persistent soil seed bank. When seedling emergence had ceased but before new seeds were shed, all soil from the upper 5 cm of 120 quadrats was removed to the laboratory. At that time, the seeds sampled were those from previous seed rains. Data description: Plant species with persistent and transient seeds were widely scattered across the range of seed mass or dimension and variances. A significant relationship was found between seed mass (or dimension) and seed persistence with persistent seeds tending to have larger mass. However, no significant relationship was found between seed shape and seed persistence. Species with persistent seeds had significantly higher seed mass than those with transient seeds (one-tailed t-test = 1.68, n = 48, P = 0.007), but there was no significant difference in shape between them (one-tailed t-test = 1.68, n = 48, P = 0.076; t-test = 1.68, n = 45, P = 0.124). Species with persistent seeds yielded significantly higher seed dimensions than those with transient seeds (one-tailed t-test = 1.95, n = 48, P = 0.029). In this study, there was no threshold in seed mass (or dimension) and shape that distinguished transient from persistent seeds. Conclusions: Species with persistent seeds have significantly larger seeds than species with transient seeds. However, species with small and/or round persistent seeds were relatively common. The underlying mechanism proposed for the observed pattern is a high proportion of large-seeded, persistent species with hard seed coat dormancy and abundant litter on the surface of the soil. Data from all eight floras studied to date suggest that significant differences in climate may determine diverse patterns in the relationships between seed mass and shape and persistence. Small and compact seeds are likely to occur in soil seed banks in humid climates, whereas large-seeded species with persistent seed banks are more likely to be abundant in arid climates. In addition, the importance of the spatial scale of investigations (or the range of habitats) is emphasized for studying the relationships between seed mass and shape and persistence.