Olea, Juglans and Castanea: the OJC group as pollen evidence of the development of human-induced environments in the Italian peninsula

Pollen data from three off-site records and twenty-six on-site (archaeological) sites are reviewed to investigate the development of cultural landscapes through the history of the olive, walnut and chestnut trees in the Italian Peninsula from the Late Glacial to late Holocene. The spread of these trees, which have been gathered or cultivated since ancient times, though not marked by high values in pollen diagrams, is an important indicator of increasing human activity and anthropization in the Mediterranean area. The sum of Olea, Juglans and Castanea percentages in pollen spectra constitutes the OJC curve. The off-site records discussed are core RF93-30 from the Adriatic Sea (last 7000 years), and cores PALB94-1E of Lago Albano and PNEM94-1B of Lago di Nemi, two lakes in the Latium region (last 13,000 years). The on-site records are located in several regions (Veneto, Emilia Romagna, Tuscany, Basilicata, Calabria, and Sicily) and in the Republic of San Marino. Their chronology spans approximately from the Bronze to the Renaissance ages, from 4200 to 500 years BP. The simultaneous presence of OJC in the off-sites and in all the archaeological sites confirms that these trees were widespread in the Italian peninsula during the last four millennia. The OJC pollen sum shows low values but it is common in Bronze age sites from northern Italy, when their percentages increase in the off-site records. In Hellenistic and Roman times, there are sharp increments of their curves in the off-sites, and values of Olea are especially high in archaeological sites of southern Italy. The highest values of OJC, especially due to Castanea, are found in the different types of records in the Middle ages. Juglans is significant but less common in both the archaeological sites and the off-sites. The cultivation of walnut and chestnut trees in pre-Roman times may have included local stands. The nurturing for wood may have had negative effects on pollen fallout while the flowering of plants was favoured to obtain fruits. As humans exploited the natural resources they interfered with the distribution of useful plants. The development of human environments in a modern sense, however, is a relatively recent phenomenon. It has largely caused the expansion of complex agrarian landscapes, including fields, pastures and groves.