Lateglacial and early Holocene vegetation development in the Gutaiului Mountains, northwestern Romania

Abstract

Pollen analyses and AMS 14C measurements were performed on lacustrine sediments and peat sequences from two former crater lakes (Preluca Tiganului, Steregoiu) situated in the Gutaiului Mountains in northwestern Romania, in order to reconstruct the vegetation development during the Lateglacial and Early Holocene. Before c. 14,700 cal. years BP (GS-2) open vegetation with shrubs ( Salix, Juniperus), grasses and herbs (e.g. Artemisia and Chenopodiaceae) prevailed in the area. Around c. 14,700 cal. years BP and coinciding with the beginning of GI-1e, Pinus expanded, and patchy vegetation with scattered Pinus stands developed. The last 100 years of GI-1e (14,150–14,050 cal. years BP) were characterised by an increase in Pinus and Betula and an expansion of open forest communities. This development was shortly interrupted between 14,050 and 13,800 cal. years BP (likely corresponding to the cold phase GI-1d), when the tree cover became reduced and open vegetation with scattered Pinus individuals became frequent. The period with a significant expansion of Betula and Picea and the formation of an open forest (including Pinus and Ulmus), which took place between 13,800 and c. 12,950 cal. years BP, is tentatively correlated with GI-1c-a. A renewed reduction in tree cover (decrease of Picea and Betula, disappearance of Ulmus) started at ∼12,950 cal. years BP and at 12,600 cal. years BP forest stands were rapidly replaced by open vegetation communities with low shrubs ( Salix, Juniperus), grasses and herbs (e.g. Artemisia and Chenopodiaceae). The period between 12,900 and 11,500 is correlated with the cold phase GS-1. At 11,500 cal. years BP, most likely as a response to the warmer climatic conditions at the beginning of the Holocene, an expansion of Betula and Alnus and, slightly later, also of Ulmus can be observed. Between 11,500 and 11,250 cal. years BP, open forests with Betula, Pinus and Ulmus were widespread in the area. At 11,250 cal. years BP dense forests dominated by Ulmus replaced the open forest type. Around 10,700 cal. years BP Quercus, Tilia and Fraxinus expanded strongly, and Acer and Corylus became established. Mixed deciduous forest with Picea dominated the upland vegetation between 10,700 and 10,150 cal. years BP. At 10,150 cal. years BP Corylus increased significantly and between 10,150 and 8500 cal. years BP, dense mixed deciduous forests with Picea and Corylus were abundant in the area. Climatic fluctuations seem to have been the driving force behind vegetation changes during the Lateglacial period, while the forest development during the Early Holocene was mainly driven by migrational and successional processes.