Middle- to late-Holocene fire history and the impact on Mediterranean pine and oak forests according to the core RF93-30, central Adriatic Sea

The high-resolution Adriatic RF93-30 core shows changes in its microcharcoal record, which correlate to terrestrial fires from the last 7000 years. Pollen and microcharcoals were transported by wind and fluvial transport from the sedimentary basin, including the Po River and other rivers flowing into the sea off the Italian east coast. Charcoal particles and pollen were counted in the same samples, and the maximum breadth and length of charcoal particles were measured. Microcharcoals with large dimensions were taken as fire indicators occurring along the near coast, as they probably arrived from short distances, the nearest being in Apulia, in southern Italy. The age-depth model was developed within the multidisciplinary PALICLAS project. Several potential fire activity increases (PFAIs) were visible as peaks in the diagram. The oldest PFAIs occurred at the middle Holocene (approximately dated to c. 6730, 5430, 4150 cal BP), others occurred at the late Holocene (c. 3760, 2660, 2240, 2030, 1930, 1510 cal BP) and during the last millennium (c. 900-865, 530, 120-96 cal BP). The two oldest peaks in the diagram, occurring in the 7th-6th millennia, showed the highest contribution of charcoal corresponding to the highest values of arboreal pollen (AP) in the sedimentary record. Although the CHAR peaks did not represent a single fire event, the diagram suggests a good correspondence between paleofire activity and terrestrial vegetation biomass during this early phase. Pollen containing black particles was observed, which suggested some grains were transported in suspension with winds from burned woods. The main unambiguous anthropogenic fire causation would have occurred during the last four millennia. From 4.2 ka, it became hard to disentangle climate and Bronze Age actions. Technology and human activity probably improved the pace of fire events, especially involving oak woods, with evidence of an increase of CHAR during the last millennium.