CHARACTERISTICS OF POLLEN ASSEMBLAGES OF SURFACE SAMPLES FROM THE NORTH-EASTERN TIBETAN PLATEAU AND THEIR IMPLICATIONS FOR VEGETATION AND CLIMATE

Abstract

65 soil samples from north-eastern Tibetan Plateau,northwest China(94.17°E～102.37°E,35.72 °N～38.05°N),were analyzed for pollen content.The pollen belong to six main vegetation types:forest,alpine shrubs,alpine meadows,temperate steppes,steppe deserts,shrub and semi-shrub deserts.The aim of this study is to provide new data on the modern pollen rain in the semi-arid to arid areas of northwest China.These data were interpreted by using diagrams of pollen percentages and numerical analyses.Our result shows that the present major vegetation communities in Qinghai area can be well defined by their pollen assemblages.Artemisia/Chenopodiaceae(A/C)ratio is sensitive to mean annual precipitation (MAP).It decreases from the alpine shrub and alpine meadow zone,through the temperate steppe,to the shrub and semi-shrub desert zone.Detrended correspondence analyses indicate that pollen assemblages have obvious relationship with the mean annual precipitation(MAP)and the July mean annual temperature (July Temp).This study also provides the theoretical basis for quantitative reconstructions of palaeoclimate and palaeovegetation based on fossil pollen spectra from the lacustrine sediments of the Qinghai Lake and Qaidam basin.