The germination ecology, including primary and secondary dormancy, mortality of seeds, and seed-bank type, of 20 fen grassland species from Northern Germany was investigated using a combination of burial and germination experiments. To analyze primary dormancy and effects of after-ripening (dry storage for 28 days) on freshly matured seeds, germination was measured at two fluctuating temperature regimes (15/25°C and 5/15°C) in the light and in darkness. Temporal changes in dormancy were investigated by burying seeds at 8–10 cm depth in nylon bags, exhuming samples at bimonthly intervals over a period of two years, and analyzing germination at the above-mentioned temperature and light treatments. Additional seed samples were retrieved five years after burial to determine seed longevity and seed-bank type. Freshly matured seeds of all species except Bromus racemosus showed primary dormancy. Dry after-ripening significantly increased germination in Parnassia palustris and Triglochin palustre. Mortality of buried seeds of Bromus racemosus, Sanguisorba officinalis, and Succisa pratensis reached 100% within 12 months (transient seed banks). All other species germinated both in the first and in the second growth period after burial and (with the exception of Briza media) showed annual changes in dormancy. For Silene flos-cuculi and Juncus filiformis, dormancy cycles were detected only in the dark treatments. Most species had a lower percentage germination in darkness than in the light, and the greatest suppression of germination in darkness was found in the small-seeded species (Juncus filiformis and Parnassia palustris). The retrieval of seed samples after five years revealed that most of the fen grassland species examined have short-term, persistent seed banks and thus are buffered against years of poor seed production and/or seedling survival. In addition, a large proportion of the species maintain long-term, persistent seed banks from which re-establishment is possible if management practices and site conditions of degenerated fen grasslands become appropriate following restoration measures.
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Vol. 24 • No. 1