Seed bank of Pinus nigra plantations in dolomite rock grassland habitats, and its implications for restoring grassland vegetation.
Dolomite grasslands of the Hungarian Central Range represent high botanical value, preserving several relic and endemic species and associations. These areas were extensively afforested with the alien black pine (Pinus nigra) during the 20th century. Recently, restoration of the dolomite grassland vegetation started in nature reserves. The soil seed bank of the black pine plantations was studied to evaluate its possible role in grassland restoration in an area 30 km NW of Budapest. Germination tests indicated an impoverishment of the seed bank of the former grassland vegetation under the studied 55-year-old forests. This trend increased with higher density of tree-canopy (92.4 and 39.6 seeds/m2 at 65% and 80% canopy cover, respectively). Many species were represented by single seeds. Six dolomite grassland components maintained a long-term persistent seed bank: Campanula sibirica, Colutea arborescens, Filipendula vulgaris, Polygala amara, Teucrium montanum and Viola rupestris. The relatively high ratio of wind dispersed seeds of weeds or species from other natural communities suggests that the removal of black pine over large areas would lead to the dominance of these species. In order to promote the immigration and establishment of the dolomite rock grassland species, a successive cutting system is proposed.