Characteristics of the modern pollen assemblages from different vegetation zones in Northeast China: Implications for pollen-based climate reconstruction

Northeast China is an essential area for studying the strength of East Asian Summer Monsoon (EASM), due to its northernmost location in EASM domain. However, the lack of sufficient modern pollen data in this region hinders an effective interpretation of fossil pollen records and quantitative vegetation/climate reconstructions. Here, 44 surface pollen samples from forest, steppe, and meadow were used to explore pollen-vegetation-climate relationships. Cluster analysis, species indicator analysis, and principal components analysis, were used to identify the discontinuous and continuous trends in pollen dataset. In addition, correlation analysis and boosted regression trees were used to investigate primary explanatory variables, while coinertia analysis and redundancy analysis to examine pollen-vegetation and pollen-climate correlations respectively. Our results show that: (1) vegetation can be well represented by surface pollen assemblages, i.e. forest is characterized by a high proportion of tree pollen (>70%) dominated by Betula (>40%) along with Alnus, Larix, and Pinus, whereas Steppe by herb pollen (>80%), dominated by Artemisia, Chenopodiaceae; (2) significant correlations exist between pollen assemblages and mean annual temperature and then mean annual precipitation; (3) pollen ratios of Artemisia/Chenopodiaceae and arboreal/non-arboreal can respectively be used as good indicators of humidity and temperature in Northeast China.