Lake sediment is important archive for reconstructing the past climate change, in which the chronological framework of sediments is the basis. Varve is a kind of sedimentary lamina formed in pairs in lake sediments, usually with one year as a cycle. Supported by the projects the Strategic Priority Research Program of Chinese Academy of Sciences “Pan-Third Pole Environment Study for a Green Silk Road (Pan-TPE)” and The Second Tibetan Plateau Scientific Expedition and Research, the authors obtained a 1-meter long sediment gravity core from Jiangco in the central Tibet Plateau, and found well preserved varves. Subsequently, core thin sections were made, and the varve and its thickness were counted and measured to obtain the chronological sequence from 81 A.D. to 2015. The precipitation in this area in the past 2000 years has been reconstructed by using the percentage of coarse-grained layer thickness in the total varve thickness, which represents the precipitation. High resolution and high-precision chronology and precipitation records can provide reliable background of climate and environmental change, and provide reference for paleoclimate simulation and the rise and fall of ancient civilization.
Airborne pollen is mainly produced and disseminated during the process of plant flowering, controlled by plant phenology and climatic conditions. As an important bioindicator of plant behavior, airborne pollen can supply information about reproductive phenology, climate and atmospheric circulations. From 2011 to 2013, airborne pollen samples were collected using a volumetric Burkard pollen trap at the Qomolangma Station for Atmospheric and Environmental Observation and Research, Chinese Academy of Sciences (QOMS, 28.21°N, 86.56°E; 4276 m a.s.l.), on the northern slope of the Himalayas. The sampler is a volumetric air-suction device capable of continuously gathering pollen and spore particles. Air is drawn in at a speed of 10 l/min, and airborne particles are deposited on a sticky tape mounted on a drum that makes one complete rotation per week. The tape is changed weekly after a complete rotation. Then, the tape is removed and cut into seven pieces, with each piece representing one day of sampling. The pieces are mounted on slides using glycerin and safranin. Identification and counting of pollen grains were performed under an Olympus BX41 microscope at 400× magniﬁcation; all pollen grains on each slide were counted . Pollen concentration was expressed as the daily pollen grains per cubic meter of air using a constant air intake speed of 10 l/min. The pollen concentration and percentage of each pollen taxon in each year were calculated. The pollen sampling and lab process were followed the standard methods to ensure the authenticity and reliability of the data. The pollen data can provides insights into vegetation response to climate change and has significance for interpreting fossil pollen records.