Holocene climate change on the northeastern Tibetan Plateau inferred from mountain-slope pollen and non-pollen palynomorphs

On the northeastern Tibetan Plateau, mountain slope sediments provide a uniquely sensitive perspective on past climate changes. Here, we report a Holocene record of pollen and non-pollen palynomorphs based on compiled data sampled from one continuous alpine slope sediment section (3780 m a.s.l.) near the Gonghe Basin. In the assemblages, higher-order plants are dominant by herbs and shrubs, mainly including Chenopodiacaee, Asteraceae and Poaceae; broadleaved and gymnosperms are very rare. The lower-order (non-pollen) palynomorphs are from fungi, pteridophytes and bryophytes. Both pollen percentages and concentrations show roughly gradual decreasing trends (from ~ 70% to ~ 30% and ~ 10,000 grains/g to ~ 2000 grains/g, respectively), indicating a deteriorating climatic trend characterized by colder and drier. Also, four phases at 8.2-7.4, 5.8-5.3, 3.4-2.9 and 1.8-1.3 ka correlate well with the coldest events that occurred at high latitudes and/or over the Tibetan Plateau. Therefore, we argue that analysis of pollen and non-pollen palynomorphs together can offer an efficient way to reconstruct palaeoclimate changes especially in sedimentary environments that have poor pollen enrichment, such as mountain slopes on the northeast Tibetan Plateau.