Revealing the vegetation, fire and human activities in the lowland of eastern Taiwan during Late Holocene

Late Holocene vegetation, climate and human impacts were investigated using palynologiacal and marco-charcoal data from lacustrine sediments from a lowland lake of eastern Taiwan. On the basis of sixteen 210Pb dates and six radiocarbon dates, a reliable stratigraphic chronology was established. The 2680 year records of vegetation history and fire frequency indicated five distinctive stages, reflecting the exhibits of climate changes and human activities. During 2680–2410 cal yr BP, the lake was shallow and the climate was relatively cool, according to the domination of wetland and upper montane forest pollen. The following period during 2410–1510 cal yr BP, the increase of low montane forest pollen and the overall high value of fire frequency indicated the warm and less humid climate. During 1510-560 cal yr BP, the low montane forest pollen remained high values, and the climate was warm and stable. During 560-130 cal BP, the low pollen concentration companying with high frequency of nearby taxa, Lagerstroemia inferred to increase in soil erosion. The period with intensive soil erosion can link to the occurrences of extremely precipitation. It may correlate to the frequent typhoons during the Little Ice Age, during which the reduction of the West Pacific Warm Pool and expansion of the Northwestern Pacific High enhanced westerly shift of typhoon track toward Taiwan and southern China. During last 130 cal yr BP, the strong impacts of human activities were indicated by the low arboreal pollen, high cultivated Poaceae, and more fire events. It is worth to note that the global temperate anomalies could be identified within this lowland lacustrine sediments, including the Medieval Warm Period and the Little Ice Age, based on the proxies of pollen-inferred temperature. Pollen signals including cultivated Poaceae pollen and pollen diversity index indicate significant human agriculture during the intervals of 2680–2410 cal yr BP, and during 1510 cal yr BP to modern time, which may be linked to the local environment changes, leading to the population variation in eastern lowland Taiwan.