Aim The forest steppe of the Transylvanian Plain is a landscape of exceptionally diverse steppe-like and semi-natural grasslands. Is this vegetation a remnant of a once continuous temperate forest extensively cleared by humans, or has the area, since the last glacial, always been a forest steppe? Understanding the processes that drive temperate grassland formation is important because effective management of this biome is critical to the conservation of the European cultural landscape. Location Lake Stiucii, north-western Romania, central-eastern Europe. Methods We analysed multi-proxy variables (pollen, coprophilous fungi, plant macroremains, macrocharcoal) from a 55,000 year discontinuous sequence (c. 55,000–35,000; 13,000–0 cal. yr bp), integrating models of pollen-based vegetation cover, biome reconstruction, global atmospheric simulations and archaeological records. Results Needleleaf woodland occurred during glacial Marine Isotope Stage (MIS) 3, but contracted at the end of this period. Forest coverage of c. 55% (early Holocene) and 65% (mid-Holocene) prevailed through the Holocene, but Bronze Age humans extensively cleared forests after 3700 cal. yr bp. Forest coverage was most widespread between 8600 and 3700 cal. yr bp, whereas grasses, steppe and xerothermic forbs were most extensive between 11,700 and 8600 cal. yr bp and during the last 3700 cal. yr bp. Cerealia pollen indicate the presence of arable agriculture by c. 7000 cal. yr bp. Main conclusions We have provided the first unequivocal evidence for needleleaf woodland during glacial MIS 3 in this region. Extensive forests prevailed prior to 3700 cal. yr bp, challenging the hypothesis that the Transylvanian lowlands were never wooded following the last glaciation. However, these forests were never fully closed either, reflecting dry growing season conditions, recurrent fires and anthropogenic impacts, which have favoured grassland persistence throughout the Holocene. The longevity of natural and semi-natural grasslands in the region may explain their current exceptional biodiversity. This longer-term perspective implies that future climatic warming and associated fire will maintain these grasslands.
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Abstract The environmental changes (vegetation history, human impact and land use, influence of the Black Sea) in the area of Lake Durankulak, northeastern Bulgaria, were reconstructed and synthesized for the last ca. 8000 years. The palaeoecological information derived from various proxies (pollen, plant macrofossils, molluscs, sediments) was compared on a regional scale with the evidence from the nearby coastal lakes Shabla–Ezeretz and Bolata. The Early Holocene xerothermic steppe vegetation, dominated by Chenopodiaceae, Artemisia and Poaceae species, and accompanied by stands of trees in moister habitats, was transformed after 6000 cal. BP into a forest-steppe, comprising oak woods with Carpinus betulus, Ulmus, Tilia, Acer. This vegetation pattern has been periodically modified, depleted and replaced by arable land or xerothermic herbaceous communities enriched with anthropophytes and ruderals, particularly after the intensification of human activities since 3300 cal. BP. The archaeobotanical evidence from the region has provided valuable information about the occupation phases and subsistence strategy of the local people since the Late Neolithic (5300 cal. BC/7250 cal. BP). Periods with cultivation of cereals (Triticum, Hordeum) and/or stock-breeding activity were interrupted by abandonment of the settlements and the arable land due to unfavourable environmental changes. The periodical connection/isolation of Lake Durankulak with the Black Sea and the periods of marine influence were recorded by changes in the composition of the fossil molluscan fauna and the lithology of the sediments, and chronologically confirmed by radiocarbon dates. The development of the coastal lakes throughout the largest part of the Holocene has been also considerably influenced by the fluctuations of the Black Sea level.
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