Secondary forest stands growing on deforested soils. How far are they from the natural forest ecosystem?

The plant composition of forest stands growing at sites of late medieval villages or prehistoric settlements or planted on previous agricultural land was studied during the past 40 years. The flora was compared with that of natural forest stands growing at undisturbed sites. The species found were divided into four groups: (1) species occurring only in natural forest, (2) species with limited colonisation ability, (3) species with good colonisation ability, (4) group of species with rapid colonisation ability. An experiment with artificial planting of soil blocks from a natural forest to a secondary forest proved to be unsuccessful, as the species persisted only in the original blocks for 5 to 10 years and disappeared after 30 years. The reason for the failing colonisation of reforested sites is supposed to be strong differences in soil structure and properties. Problems with migration of species diaspores may be of secondary importance.