SOIL SEED BANK COMPOSITION IN DIFFERENT SUCCESSIONAL STAGES OF A SPECIES-RICH WOODED MEADOW IN LAELATU, WESTERN ESTONIA

We studied the seed bank of a calcareous grassland in four sites with different management history: original old grassland, which has been d escribed as one of the richest plant communities in Europe, long-term restored grassland, which has been overgrown in the seventies, recentl y overgrown (ca. 20 years ago) and long-term overgrown grasslands. The seed banks in grassland sites at Laelatu were small both in size and number of species. The number of species and seeds in the seed bank de clined significantly from managed grasslands to closed overgrown commu nity. The highest species richness of the soil seed bank (number of sp ecies per soil volume) was found in the managed grassland sites, the s eed density in the bank was the highest in the long-term restored gras sland site. About one third of ail the grassland species were found in the seed bank. The proportion of species in the established vegetatio n - represented also in the bank - was higher in overgrown sites. Howe ver, ordination (Correspondence Analysis), which also took into accoun t species frequencies, showed that the similarity between established vegetation on plots and seed bank samples decreased from original gras sland to closed overgrown grassland. The persistence of the seeds of o nly 8-10 typical grassland species in the seed bank of overgrown grass land sites makes the significance of the seed bank for community resto ration quite small. (C) Elsevier, Paris.