Matskási István (szerk.): A Magyar Természettudományi Múzeum évkönyve 88. (Budapest 1996)
Csontos, P., Horánszky, A. , Kalapos, T. ; Lőkös, L.: Seed bank of Pinus nigra plantations in dolomite rock grassland habitats, and its implications for restoring grassland vegetation
Earlier this century the grassland habitats of dolomite plateaux and hillsides were afforested with the non-indigenous Pinus nigra ARN. (HÉDER 1953), causing significant changes in the original vegetation (BORllini 1956, BÓDIS 1993). Some further unfavourable effects of the black-pine plantations are briefly summarized from a nature conservational point of view by CSONTOS & LŐKÖS (1992). Recently a strong need has emerged for the restoration of the previous grassland vegetation in the place of existing pine plantations within nature reserves. However, one may doubt the success of restoration efforts because the herb layer seems to be increasingly changed and impoverished with increasing age and canopy closure of the pine stands (BORHIDI 1956, BÓDIS 1993). Sometimes this process terminates in a "nudum" type forest understory in the case of old stands (above 50 years) (BORHIDI 1956). Therefore, when these forests are cut for grassland restoration purpose the following must be considered: a) How big is the risk of soil erosion? (Especially where the black pine forests exist on steep slopes.) b) Are the grassland species able to recolonize the areas even if seed sources are relatively far away? c) Do the grassland species have significant seed bank in the soil to support successful recolonization? The last question is studied in this paper. Direct seed bank study of dolomite grasslands has not been done yet in Hungary, however VlRÁGH & GERENCSÉR' s (1988) paper on a secondary steppe community contains seed bank data for some species in common with dolomite grasslands. Papers dealing with various vegetation types of the Atlantic Europe, though large in number, generally consider different species pools (VYVEY 1989«, b). However, some studies under ecological conditions more or less similar to our case (such as investigations on some limestone grasslands, or habitats should maintain limestone grassland, if undisturbed) reported poorly developed seed bank beneath the standing vegetation (DONELAN & THOMPSON 1980, GRAHAM & HUTCHINGS 1988), while other authors found a somewhat better developed seed bank, but mainly composed by subordinated species of the studied grasslands (RYSER & GlGON 1985, POSCHLOD etal. 1991). The papers above generally agreed on discussing the vulnerability and difficulties of re-establishment of these species-rich communities. The purpose of this study is to describe the soil seed bank under black pine plantations on dolomite grassland habitats and to discuss some implications of this for the restoration of the grassland vegetation. MATERIALS AND METHODS The research area is located about 20 km NW of Budapest, near the village Pilisszentiván, at an elevation of 300 m. This hilly region is formed by Triassic dolomite and due to the continuous physical erosion of its bedrock, steep slopes and shallow soils are characteristic of the area. Within the research area several hillsides are covered by Pinus nigra of which the following two were selected for soil seed bank studies:
