Modern pollen assemblages of surface samples and their relationships to vegetation and climate in the northeastern Qinghai-Tibetan Plateau, China

We use a data set of 86 surface pollen samples from moss polsters and surface soils from northeastern Qinghai-Tibetan Plateau to explore the relationship between modern pollen assemblages and contemporary vegetation patterns. The samples span seven main vegetation zones from east to west: mountain forest, alpine shrub, alpine meadow, temperate steppe, steppe desert, shrub/semi-shrub desert and desert. Principal components analysis (PCA) was used to determine the relationships between modern pollen, vegetation, and regional climatic gradients. The results show that the major vegetation communities occurring today in the northeastern Qinghai-Tibetan Plateau can be clearly differentiated by their modern pollen assemblages. The representation of surface pollen varies with genera and species. For instance, relative to Betula, a low representation of Picea and Cupressaceae was found in the forest zone; Artemisia, Chenopodiaceae and Ephedraceae had high representation values, while Cyperaceae, and Nitraria showed values in the middle range, and Poaceae, Asteraceae, Tamarixaceae, Calligonum, Polygonaceae, Ranunculaceae, Fabaceae, Scrophulariaceae and Primulaceae had low representation values. Rosaceae have low representation values in the sampling sites in alpine shrub community where the dominant plant species are Potentilla fruticosa and Potentilla glabra. PCA results indicated a high correlation between the modern pollen assemblages and mean annual precipitations (MAP) and July temperature (Tjuly). The Artemisia/Chenopodiaceae (A/C) ratio is sensitive to variations in MAP in this region and is a useful tool for qualitative and semi-quantitative palaeoclimate reconstruction on the northeastern Qinghai-Tibetan Plateau.