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Vegetation dynamics during previous warm interglacial periods shed light on the human impacts on natural ecosystems during the Holocene. However, reliable terrestrial records that span such periods are rare and provide little information on regional scale. Here we present a high-resolution marine pollen record from the northern South China Sea, which reveals that during five peak interglacial periods, Marine Isotope Stages 13a, 11c, 9c, 5e and 1 (the Holocene), the vegetation successions in southern China were similar. At the beginning of each interglacial period, tropical rainforest conifers, which include Dacrydium, Dacrycarpusand Podocarpus, and associated broadleaved taxa, such as Altingia, expanded quickly at the expense of the subtropical/temperate montane conifer Pinus. Near the end of the warm periods, Pinusrecovered and the tropical taxa retreated. However, the Holocene displays subtle but significant differences in which the species turnover was interrupted and the rainforest conifers did not fully expanded. The Mg/Ca-based sea surface temperature record from the same site reveals that temperature was the major control of the rise and fall of the peak interglacial vegetation. However, exceptionally high charcoal fluxes during the Holocene suggest that human activities through land-use modifications completely, and possibly permanently, altered the natural vegetation trend five to six thousand years ago.

Abstract: Pollen grains deposited in marine sediments are transported from land to sea by wind or surface water flows. We analyzed pollen collected from the air and seawater from the coast of the Yellow Sea near China and into the western Pacific Ocean between December 2008 and January 2009 during the cruise “KX08-973”. Results showed that abundant pollen grains of Artemisia and Chenopodiaceae were probably transported to the continental shelf of the East China Sea, the East Philippine Sea and the equatorial regions of the Pacific Ocean by the winter monsoon. Some pollen may have even traveled over 2000 km from the East Asia continent to the tropical Pacific Ocean. However, a gradual decline of temperate components and an increase in tropical components was observed towards the tropical regions. Fern spores were rare in the air samples, but much more abundant in seawater samples, even though they were collected in nearly the same areas, which indicates that most fern spores were carried to the ocean by flowing water. These results suggest that the winter monsoon may be the major pollen carrier and transporter in the study area during winter.