Long-term dynamics of the East European forest-steppe ecotone

Abstract

Question: The European forest-steppe ecotone extends over 6,000 km from the Carpathian to the Ural Mountains. It is extensively used for agriculture with very few patches of semi-natural vegetation. Little is known about the history of the forest-steppe ecotone in Eastern Europe and here we examine its Holocene dynamics and stability and investigate when it was transformed to the modern agro-pastoral landscapes. Location: Mid-Russian Upland. Methods: We summarize the information from five pollen diagrams for the last 7,000 years and estimate forest cover using the best modern analogue technique. We use the PCA and principal curve analysis to evaluate compositional changes. Results: The pollen data suggest that the East European forest-steppe boundary was located 50–70 km further northwest from the presumed present position during the period 7,000–4,500 cal yr BP. After 4,500 cal year BP, it moved approximately 100–130 km to the southeast. Since 2,000 cal year BP land use affected the boundary, while a total forest clearance and transformation to agricultural landscapes took place in the last 400 years. Pollen data indicate a NW–SE direction of the forest-steppe vegetation gradient. Prior to clearance, open lime–pedunculate oak forests existed in the NW, while the south was characterized by pine woodlands with an admixture of oak and lime with 20%–40% forest cover. Conclusions: The East European forest-steppe ecotone is sensitive to climate change. The Late Holocene expansion of forest cover is in agreement with evidence suggesting an increase in moisture availability during this time. The rapid recovery to a similar composition after human disturbance indicates a high resilience of woodland in the ecotone, which may be connected to a naturally high disturbance regime, possibly through fire. The information revealed on the position of the gradient and natural composition of the forest is currently not depicted in maps of the potential natural vegetation.