Middle to Late Holocene vegetation shifts in the NW Transylvanian lowlands (Romania)

The Iaz peat bog, located in northwestern Transylvania at 300 m a.s.l., was cored to study the Middle to Late Holocene vegetation shifts in the area. The pollen record is supported by seven 14C datings. The base of the sequence starts in the Middle Holocene, when the outer woodlands were dominated by Corylus avellana together with other components of the Quercetum mixtum. The local establishment of Carpinus betulus occurred at 5700 cal. yr BP with maximum values at around 4900 cal. yr BP. At 4800 cal. yr BP, Fagus sylvatica became locally established and expanded, possibly as a result of moist climatic conditions and dominated the mesothermophilous woodlands from 4300 cal. yr BP onwards. During the periods of greater moisture, the deciduous forest was overgrown by the hygrophilous Alnus glutinosa belt. Indications of human activities in the area were recorded since 6300 cal. yr BP, when Cerealia and Secale pollen and other ruderal taxa start to appear regularly throughout the sequence. Although intense at times, the anthropogenic factor only played a major role in the vegetation changes during the last 635 years