Rapid burial has differential effects on germination and emergence of small- and large-seeded herbaceous plant species

The dynamics of many plant populations essentially depend upon seed and seedling stages, and a persistent seed bank may give species an opportunity to disperse through time. Seed burial is a decisive prelude to persistence and may strongly influence seed-bank dynamics. The fate of buried seeds depends on species-specific traits, environmental conditions and possibly also burial mode. We tested seed germination, seedling emergence and growth of the co-occurring herbaceous flood-meadow species Arabis nemorensis, Galium wirtgenii, Inula salicina, Sanguisorba officinalis and Selinum carvifolia in response to the experimental manipulation of burial depth (0, 1, 2, 4, 8, 12 cm) and substrate type (sand, clay). Increasing burial depth led to decreased germination, emergence and growth in all species studied, and seedling growth differed significantly between substrate types. The responses of species differed on an individual basis, but also showed a higher-ranking pattern based on seed size. Larger-seeded species were able to emerge from greater depths and experienced less depth-mediated growth inhibition than smaller-seeded species, which, in turn, had higher survival rates during burial and were less likely to experience fatal germination. Based on these results, we suggest that herbaceous flood-meadow species have developed two different seed-size based strategies for coping with the extreme recruitment conditions prevailing in flood meadows, the balance of which seems to be maintained by disturbance events.