Holocene millennial-scale vegetation changes in the Yugu floodplain, Kongju area, central South Korea

摘要

To understand vegetation responses to past climate change on millennial timescales, the Holocene record of floodplain vegetation change in central South Korea was reconstructed using the stable isotopic composition (δ~(13)C) and pollen in buried soils. Low-volume overbank deposition of fine-grained alluvium by Yugu stream over the past 10,000 years has produced a sequence that is well suited for δ~(13)C analysis of soil organic matter. The δ~(13)C values varied between -25‰ and -20‰ during the Holocene, showing significant millennial-scale fluctuations in five stages (11,000-8900 cal BP, 8900-6100 cal BP, 6100-3300 cal BP, 3300-1200 cal BP, and 1200 cal BP to present). The abundance of C_4 plants, estimated from a binary mixing model, changed from approximately 17-57%. During the stages from 3300 to 1200 cal BP and from 8900 to 6100 cal BP, C_4 plant abundance and the percentage of arboreal pollen were high, but the percentage of spores (mainly moss) and the freshwater algal sum were low, indicating more arid environments. Temporal comparison of C_4 plant abundance change during the Holocene with other reconstructed climate data from East Asia suggests that millennial-scale vegetation change (or aridity change) in central South Korea was generally more synchronous with regional climate change during the late Holocene than during the early to mid-Holocene. This study suggests that the past vegetation in the Yugu area has evolved in response to summer monsoon intensity in a non-linear manner.