Vegetation and fire history of the Euganean Hills (Colli Euganei) as recorded by Lateglacial and Holocene sedimentary series from Lago della Costa (northeastern Italy)

摘要

We reconstruct the vegetational and fire history of the Colli Euganei and northeastern Po Plain from c. 16 500 cal. BP to the present using AMS-dated sedimentary pollen, microscopic and macroscopic charcoal records. Our study site, Lago della Costa, is the only natural water basin with an undisturbed late-Quaternary sediment accumulation in the northeastern Po Plain. Mixed coniferous-deciduous forests occurred since at latest 14 500 cal. BP. Gradual expansion of e.g. Alnus glutinosa and Carpinus betulus is documented after c. 11 000 cal. BP. A further expansion of Abies alba and Alnus at 9200 cal. BP coincided with a population buildup of these species in the Insubrian region c. 200 km northwest of our site. A further increase of Alnus about 6400 cal. BP was accompanied by an expansion of Castanea sativa and Juglans regia as well as meadow and field plants. This vegetational change was contemporaneous with a huge increase of regional and local fire activity. Our data suggest that fire disturbance favoured strong and moderate re-sprouters, e.g. Alnus, Carpinus and Castanea, whereas fire-sensitive taxa, e.g. Tilia and Abies were disadvantaged.The close link between crops, weeds and fire activity suggests human impact as the main source of changes in Neolithic vegetation and fire regime.To our knowledge these are the oldest palaeobotanical data suggesting the cultivation of Castanea and Juglans in Europe and elsewhere. Our pollen and charcoal records document the subsequent cultivation of Castanea,Juglans, Olea and Cerealia t. during the Bronze Age (4150-2750 cal. BP). Subsequently, intensification of land use continued during the Iron and Roman Age and Medieval times. In contrast with other northern Italian sites vegetation around our site was always rather open with a substantial proportion covered by grassland. We explain this peculiarity of the site by its location near river banks and floodlands.