Late Holocene persistence of Abies alba in low-mid altitude deciduous forests of central and southern Italy: new perspectives from charcoal data

摘要

Questions: Pollen data for Abies alba Mill., a key European tree species, show broad occurrence in the Italian peninsula in the early to mid-Holocene diffusion (until ca. 6000 yr ago) along the Italian peninsula and a strong decline/local extinction starting ca. 5000 yr ago. This decline has been attributed to climate change. Recently, high-resolution pollen studies, mainly in northern Italian sites claim that A. alba disappearance was mainly due to human impact. We examined the presence of A. alba in archaeological sites of southern and central Italy in order to trace the late Holocene history (last 3000 yr) of this tree and enhance understanding of its role in pre-anthropic vegetation and of human involvement in its decline.Location: Central and southern Italy.Methods: Anthracological analysis was conducted in six archaeological layers at the archaeological site of Trebbio-Spinellina (800-600 BC, Sansepolcro, Tuscany). A critical analysis of wood/charcoal literature relevant to Abies in central and southern Italy was used to corroborate the results of Trebbio-Spinellina. Charcoal records from archaeological sites have been compared with the current distribution of A. alba.Results: At Trebbio-Spinellina, A. alba charcoal is present in all contexts examined, together with mesophilous broad-leaf taxa (Quercus deciduous, Carpinus betulus, Ostrya carpinifolia, Corylus avellana). A low charcoal percentage of Fagus sylvatica and Taxus baccata is also found; evergreen taxa are mainly represented by Quercus ilex with occasional shrubs (i.e. Viburnum, Cistus, Erica). In the literature, we identified several peninsular and insular Italian archaeological sites showing charcoal evidence of Abies, accompanied by deciduous oaks, mainly Q. cerris, and other broad-leaf mesophilous trees, dating from the Iron Age to the Middle Ages. All sites, except one, lie at less than 600 m a.s.l., and far from present-day A. alba communities.Conclusion: Results call for a reworking of the prevailing paradigm of A. alba as a relic mountain species. Indeed, A. alba once grew at lower altitudes than currently and was associated with deciduous oaks, mainly Q. cerris, and other mesophilous broad-leaf trees. This evidence calls into question the suitability of the Potential Natural Vegetation (PNV) concept usually applied in the floristic approach. The recent population decline is attributable to human activity rather than to climate change. Finally, the persistence of A. alba until the late Holocene calls into question the assumptions that it is a relic species with no potential to expand its spatial range