On the basis of pollen analysis from two stratigraphical profiles at a valley pass of Baohuashan Mt. and Guantang, integrated with macrofossil data and radiocarbon dating, this study shows a stable climate period with warm and wet conditions between earlier than 6 700 and 5 600 aBP. There was a transitional period of climate fluctuations with cold and/or warm, dry and/or wet conditions between 5 600 and 5 100 aBP. A change in climate with warm and wet conditions registers a stable period from ca 4 400 to 4 000 aBP, and a back to cool condition after 4 000 aBP. Furthermore, according to the relationships between modern vegetation and pollen spectra in the natural protective area of Baohaushan Mt. and between sedimentary pollen and macrofossils, the presence of ca 10% of pollen Cyclobarlanopsis and Castanopsis indicates that a middle subtropical evergreen broad leaved forest did exist in the lower reaches of Yangtze River, where human activities have affected the areas since the Neolithic Age. On the other hand, based on the stratigraphical characteristics, the erosion surfaces and secondary loess deposits indicate unstable conditions, i.e. related to the lowing of sea levels while deposits of mud and peat imply a warm and wet condition and the rising of sea levels which is very typical in the lower reaches of Yangtze River.
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