Are western European oak forests man-made constructs? The pedoanthracological perspective

Fagus sylvatica L. is among the most competitive trees in European temperate deciduous forests on well-drained but not too dry soils and is known to be a major species in the mature stages of natural succession over large areas. However, even under favourable conditions, it is often sporadic or even absent from present-day stands whereas Quercus spp. are dominant. Based on written sources, the predominance of Quercus spp. has been identified as a potential heritage of historical management. To test the hypothesis that past human practices caused the replacement of Fagus by Quercus spp. on well-drained soils, we carried out a soil charcoal analysis on current mature Quercus spp. stands in 19 forest sites of the Lorraine Plateau in northeastern France. 'Megacharcoal' assemblages were extracted from soil trenches and taxonomically identified. Our results, based on more than 5600 charcoal pieces, identified 19 taxa and showed the presence of Quercus and Fagus in all sites. Quercus was dominant, followed by Carpinus and Fagus, as it is today in the on-site forests, except for Fagus, which is not observed in any of the studied stands. Other taxa, such as Prunus, Populus, Betula, were present at lower abundances, occurring in only a few sampling sites. The 71 radiocarbon dates indicated that i) a Fagus forest had been in place during the Bronze Age, without any dated oak pieces found; ii) Quercus became common from the end of the Bronze Age, iii) and was mixed with Fagus from the middle of the Iron Age. These results provide a new evidence that historical forest management in western Europe caused the replacement of Fagus by Quercus, and therefore the manipulation of forest stand species composition started during the Bronze Age.