Search

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 ShablaeEzeretz 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.

Pollen analysis of sediments from the glacial Lake Trilistnika (2216 m) in the Northwestern Rila Mountains (Bulgaria), supplemented by 13 radiocarbon dates, allowed the reconstruction of the palaeoenvironment and vegetation history in postglacial time. The exact time of the cirque glacier retreat is still under discussion but the lake was free of ice before 15,000 cal. BP, when sedimentation of gray silt began. The lateglacial vegetation, composed of Artemisia , Chenopodiaceae and Poaceae, with isolated stands of Pinus and Juniperus – Ephedra shrubland, dominated during the stadials and partly retreated during the Bolling/Allerod interstadial complex. The afforestation in the early Holocene (11,500–7800 cal. BP) started with the distribution of pioneer Betula forests with groups of Pinus ( P. mugo , P. sylvestris and P. peuce ) at mid-high altitudes, and Quercus forests with Tilia , Ulmus , Fraxinus , Corylus below the birch zone. The change to more humid and cooler climate ca. 7800–7500 cal. BP favored the vertical migration of Abies , P. sylvestris and P. peuce . The establishment of Fagus sylvatica took place after 5200 cal. BP, when pure or mixed beech communities were formed. The last tree which invaded the coniferous belt between 4300 and 3400 cal. BP was Picea abies . The first expansion maximum of spruce was recorded after ca. 2700 cal. BP. The vegetation development in historical times was also influenced by human interference, indicated by the continuous presence of pollen anthropogenic indicators such as Triticum , Secale , Hordeum , Plantago lanceolata , Rumex , Scleranthus , Juniperus .