Quaternary Refugia of North European Trees

An attempt is made to investigate the nature of cold-stage distributions for those forest trees which today extend to northern Europe. Evidence is taken from the pollen record of the present and earlier interglacials, a model of past climate, modern tree distributions, and physiography of southern Europe. The trees occupied mid-altitude sites in the mountains of southern Europe, especially in the western Balkans and Italy during the last cold stage. These areas would have had a suitable climate, and it is argued that the trees could easily have survived there at densities low enough to escape detection in the pollen record. Most taxa which spread north at the beginning of an interglacial become extinct in the northern part of their ranges, and do not retreat south at the end of the interglacial. The survival of these trees in southern Europe through a warm stage may be at least as important for long-term Quaternary survival in Europe as survival during a cold stage.