A preliminary mapped summary of holocene pollen data for northeast China

Maps of pollen data have long been unavailable for continental Asia despite their importance for paleoecological and paleoclimatic studies. Pollen data from 65 Holocene sites have allowed the mapping of eight pollen taxa and seven time slices for Northeast China. These pollen maps show significant vegetation changes during the last 10,000 years in the current forest regions of Northeast China, with the early Holocene characterized by widely distributed Betula trees, the mid-Holocene by the development of temperate deciduous forest mainly consisting of Quercus and Ulmus trees, and the late Holocene by the marked increase in the abundance of Pinus trees and the development of temperate mixed conifer and deciduous forest. An unexpected finding from the pollen mapping research is the south-to-north propagation of the mid-to-late-Holocene forest decline, which may have been caused by the persistent human activities and the gradually northward expansion of agriculture during the last 5000 years. It is thus evident that caution has to be taken when reconstructing the mid-to-late-Holocene climates from pollen records in some regions of Northeast China. The classic paleoclimate reconstruction for the southern part of the study area and possibly for North and Northwest China needs to be re-evaluated.