THE VEGETATIONAL HISTORY OF THE BALKANS

The vegetational history of the Balkans from the last glacial through to present features a dynamic system not subject to immigration of additional taxa. Many temperate taxa appear to have survived in this region during the last glacial in low but persistent populations. Evidence suggests that a greater diversity of taxa existed in the mid to high altitude sites probably where the climate was more humid. At the lateglacial/Holocene transition many tree taxa expanded simultaneously with no evidence of the time-transgressive appearance of taxa which is taken to be indicative of differential immigration in northern Europe. Expansion of temperate woodland was at least 1000 years earlier than in northern Europe suggesting that this was the minimum time for migration of temperate trees into northern Europe. Changes in the composition of the early Holocene woodland included expansion of Pistacia between 9000 and 8000 C-14 BP, a change in the forest dominants between 8000 and 7000 C-14 BP, and the appearance and increase of Carpinus orient./Ostrya, Abies, Carpinus betulus and Fagus between 7500 and 5000 C-14 BP. Since all types were present in the region from the lateglacial, it is suggested that factors other than migration are responsible for their population increase. These factors are considered and include climate, soil development, establishment time and anthropogenic disturbance. Development of the present day landscape started at approximately 4500 C-14 BP with the onset of anthropogenic disturbance. Clearance resulted in the increase of open ground herbaceous types with grasses, Cerealia-type and Plantago lanceolata. New trees also to become established included Juglans, Olea, Castanea and Platanus. At least two of these types (Juglans and Castanea) were present in the Balkans during the lateglacial suggesting that although some types were imported by the Greeks/Romans others may have expanded in situ as a result of a favourable niche being created by anthropogenic disturbance.