Pollen record of climate change during the last deglaciation from the eastern Tibetan Plateau

forests (1600–2200 m a.s.l.), dominated by Lauraceae, Quercus, and Acer. 3) Mountain conifers (2000–3600 m a.s.l.), dominated by Tsuga, Picea, Pinus, Abies, and Quercus aquifolioides. 4) Alpine shrubs and meadows (> 3600 m a.s.l.), dominated by Kobresia setchwanensis, Kobresia capillifolia, and Polygonum etc. The economic trees are mainly Juglans regia, Prunus salicina, Malus pumila, and Zanthoxylum bungeanum [21]. A dataset analysis of the surface pollen on the TP indicates that the pollen buried in the sediments have the potential to reflect the inten- sity of the Asian Summer Monsoon at that time and provide a simple and potentially practical proxy for the study of the evolutionary history of the Asian summer monsoon [22]. 3. Material and methods The Xinmocun lacustrine sediments are dominated by silt (~76.6%) and have an average median particle size (Md) of 10.5 μm [18], making them suitable for pollen analysis [Fig 2B]. Pollen samples were collected from the section at intervals of 20 cm. Approximately 80 g of each subsample was processed following the newly revised palynological procedures described by Xu et al. [23], including treatments with 15% HCl and 3% NaOH, drying for 7–8 h in an oven at 85˚C, heavy liquid separation with a KI solution (specific gravity, 1.74–1.76), treatment with 40% HF and 15% HCl, and sieving (7 μm) if necessary. All samples were centrifuged and washed with distilled water after each step. The prepared specimens were mounted in glycerol for identification. All samples were processed at the State Key Laboratory of Earthquake

Dynamics, Institute of Geology, China Earthquake Administration (CEA). 4. Pollen record AMS 14C dating of black carbon grains and optically-stimulated luminescence (OSL) dating of quartz grains have different signal sources and dating principles. Applying both methods to Fig 1. DEM of the eastern margin of the Tibetan Plateau illustrating the geomorphology and drainage systems (https://viewer.nationalmap.gov/advanced-viewer/). The star denotes the location of the Xinmocun lacustrine section. https://doi.org/10.1371/journal.pone.0232803.g001 PLOS ONE Last deglacial pollen reocord from the eastern TP PLOS ONE | https://doi.org/10.1371/journal.pone.0232803 May 6, 2020 3 / 12