Late Holocene climate and vegetation changes at Lake Akgöl (Samsun, Türkiye)

The AKGÖL–02 sediment core provides a high-resolution Late Holocene palaeoenvironmental archive, offering detailed regional vegetation dynamics, climate variations, and human impact. The AKG-1 pollen zone is characterised by a high percentage of arboreal taxa, including Carpinus betulus , Fagus , and deciduous Quercus species. This indicates a warm, humid regional climate with well-developed forest cover. Based on the pollen-based quantitative climate reconstruction, cross-validation results demonstrate the robustness of the model, particularly with regard to plant-available moisture (α) and mean temperature of the coldest month (MTCO). The model also performs well concerning summer temperature (MTWA) and growing degree days above 0 °C (GDD0). Reconstructed MTWA values reveal a gradual cooling trend from around 1300 to around 800 yr BP, interrupted by short-term warming around 1000 yr BP. This was followed by a warming phase until around 400 yr BP, after which there was a subsequent cooling. MTCO remained relatively stable until around 500 yr BP, after which it increased towards 200 yr BP. Meanwhile, plant-available moisture increased steadily and peaked around 800 yr BP, after which it declined, indicating a transition from humid to drier conditions. In parallel with climatic changes, the pollen record provides clear evidence of increasing human activity. The presence of anthropogenic indicator species such as Plantago , Rumex , Populus , Juniperus, and Quercus ilex indicates landscape disturbance linked to settlement and land use. The co-occurrence of Sanguisorba minor –type and Caryophyllaceae pollen indicates an increase in agricultural and pastoral activities, which became particularly evident after 510 yr BP. The widespread presence of Pinus pollen, particularly in the AKG–1 zone, suggests enhanced colonisation of disturbed areas rather than purely climatic control. In the upper part of the core (AKG–5a and AKG–5b), the significant increase in non-arboreal taxa (notably Poaceae) and the appearance of Cerealia -type pollen indicate intensified agricultural activity and a transition to more open landscapes.