Question: What is the importance of the seed bank in the maintenance of the restoration potential of a 60-year-old abandoned calcareous grassland overgrown by Pinus trees?

Location: ‘Les Pairées’, province of Luxembourg, Belgium.

Methods: The seed bank and the above-ground vegetation were surveyed in three adjacent stands, previously forming a unique calcareous grassland: a 60-year-old Pinus forest, a four-year-old clear-cutting and a typical calcareous grassland. Floristic diversity was compared among stands and between vegetation and seed bank.

Results: The species richness of the vegetation and the seed bank was significantly lower in the Pinus forest. More floristic similarities were found between the clear-cutting and the calcareous grassland. Seed bank was essentially transient, dominated by annual species. Its correspondence with the above-ground vegetation was weak.

Conclusion: Very few calcareous grassland species have persisted in the Pinus stand. Four years after clear-cutting, the stand was nearing restoration towards a calcareous grassland. Seed longevity in the soil was not the most explicative factor. Dispersal of propagules from adjacent sources was also important.

Nomenclature: Lambinon et al. (1992).