Zelkova carpinifolia (Pallas) K. Koch in Holocene sediments of Georgia-an indicator of climatic optima

Six major climatic optima occurred in Georgia through the course of the Holocene, the longest and warmest of which occurred in the mid-Holocene and reached its maximum between 6000 and 5500 Cal. yr BP. During that period, Zelkova and Castanea forests were widespread. In Western Georgia, the upper tree line was elevated by as much as 300 m above its present-day level. In semiarid Eastern Georgia, the tree line may have been 500-600 m higher. Other climatic optima are seen in late-Holocene pollen spectra dating to 3800-2500 Cal. yr BP and 1350-800 Cal. yr BP.