POPULATION PROCESSES AT THE GRASSLAND-SCR UB INTERFACE

The flora of central Europe is rich in species of calcareous grassland s and of scrub. In the same area the natural vegetation before human i nterference was predominantly forest in which the majority of these sp ecies were probably confined to temporary openings of the canopy (gaps ), or to forest edges where trees are excluded for edaphic or climatic reasons (rocky outcrops, alpine timberline, riversides). Shrubs and h erbaceous species of these primary edges became abundant under human i nfluence in extensively used grasslands, hedgerows and scrublands. At these sites the grassland-scrub edge shifts spatially depending on the intensity of agricultural management, i.e. either cutting of woody sp ecies or abandonment of grassland. Primary forest edges, on the other hand, are long-lasting habitats with only minor successional changes, but even here temporary shifts of the edge are to be expected after hu rricanes, fire, floods or unusual drought which are detrimental for wo ody species. The vegetation of primary and secondary forest edges has been frequently described. However, studies of the population processe s along and across these ecotones are scarce, although these processes are of pivotal importance for the response of grassland and scrub com munities to changes in the edge structure. This contribution reviews r esearch on population dynamics at the grassland-scrub interface. The r esults are discussed with respect to management and to nature conserva tion.