SOIL SEED BANKS IN LOESS GRASSLANDS AND THEIR ROLE IN GRASSLAND RECOVERY

Loess grasslands are among the most species-rich grasslands in Europe. In many regions only species-poor degraded fragments of formerly species-rich loess grasslands remained due to the agricultural intensification in the last century. To preserve and restore loess grasslands it is necessary to understand, how soil seed banks can contribute to the maintenance of diversity. We studied the vegetation and seed banks of (i) a loess grassland in a semi-natural state and (ii) a degraded loess pasture. We found that species richness was significantly lower in the degraded loess pasture (10.2 species/m(2)) than in the semi-natural loess grassland (27.0 species/m(2)). Mean seed bank densities were quite similar in the two grassland types (22,800 and 20,200 seeds/m(2), respectively). Out of the frequent graminoids in the vegetation, only Poa angustifolia possessed considerable dense seed banks. Forb species having considerable seed banks were mainly disturbance-tolerant species (e.g. Euphorbia cyparissias, Galium verum or Hypericum perforatum). Most characteristic forb species possessed only sporadic seed banks (e.g. Filipendula vulgaris, Pimpinella saxifraga and Salvia nemorosa). Our results suggest that seed banks have only a limited role in the recovery of loess grasslands.