Influence of human impacts on modern pollen assemblages and an assessment of their reliability in reconstructing climate in eastern China

Abstract

Understanding the relationship between modern pollen, vegetation, and climate is essential for the reconstruction of paleoenvironments and human land use from fossil pollen spectra. In this study, we collected modern pollen data from natural vegetation and human-disturbed vegetation in eastern China. Results reveal that modern pollen assemblages reflect their natural or human-disturbed vegetation, and differ between northern and southern sample sites in eastern China. Natural vegetation communities are dominated by arboreal taxa, mainly Pinus, Castanopsis, Quercus, and Betula. Farmland, which is the dominant type of human-disturbed vegetation, is dominated by herbaceous taxa particularly Cerealia Poaceae (>35 μm), Poaceae, Chenopodiaceae, and Brassicaceae. In eastern China, pollen assemblages of north China are mainly Betula, Artemisia, Chenopodiaceae, Cerealia Poaceae, Brassicaceae, and Ranunculaceae, while pollen assemblages of south China are mainly Castanopsis, Quercus, Poaceae, Cyperaceae, and Euphorbiaceae. Poaceae, Cerealia Poaceae, Brassicaceae, and Chenopodiaceae from human-disturbed vegetation is mainly distributed at low elevations and has a smaller elevational range than natural vegetation. Pollen assemblages from natural vegetation perform better at reconstructing climate than pollen assemblages from human-disturbed vegetation in eastern China. Mean annual precipitation (Pann) is a better predictor than mean temperature of the coldest month (Mtco) and mean temperature of the warmest month (Mtwa). In this study, surface pollen assemblages from human-disturbed vegetation still reflect the characteristics of the local vegetation and can still be used to reconstruct climate. Nonetheless, for more accurate results, pollen assemblages from natural vegetation communities should preferentially be used in reconstructions.