| Abstract: | There are two peat fields, the Maohebei peat field and Daziying peat field, both situated in the delta of the lower reaches of the Liao River in the Eastern Hebei Plain, North China. The peat bogs were deposited at 10000–3500 years ago. From the point view of vegetational history, the pollen assemblage zones correlated with the radiocarbon dating materials are established. On this basis the profile may be divided into three zonation systems. Zone M-l, 10000–9000 14C yr. BP. The temperate needle leaf and deciduous woodlots scattered among herbs, with a mild and cool climate. It can be correlated to the Boreal or the Anathermal interval. Zone M-2, 9000–5000 BP. Pinus and Quercum mixtumum ( Quercus, Ulmus, Tilia, Corylus) woodland and Vermuth steppes, with warm and semihumid climate. And about 7500 BP a maximum warm took place. It can be correlated to the Atlantic. Zone M-3, 5000–3500 BP. Pinus-Quercus woodland and Vermuth steppes with warm and semihumid, correlated to Subboreal. Both M-2 and M-3 can corrspond to the Hypsithermal interval of the Holocene subdivisions, i.e. the Optimum. In this interval some subtropical elements sppeare in the assemblage, such as Myrica, Antidesma, and Fagara which reflect that the weather might be warmer than that of the present in the same region. Some ecological dynamics of the vegetation are expressed in the assemblages. When climate became warm from Boreal to Atlantic, Corylus increased a little earlier than other deciduous but soon decreased. Ulmus declined at 5000 BP. This reflects situation is just the same as in North Europe. The woodland destroyed by human activities in culture and agiculture might be an important factor of vegetational and environmental changes. However the great increase of Pinus and Artemisia following the decrease of Ulmus and Tilia gives effective support to the tendency of climatic change, becaming cooler and drier in the Sub- boreal of Hypsithermal interval. This is an attempt to establish the pollen percentage diagram and pollen influx diagram by mean of exotic pollen. The pollen influx record shows similarities to that of the pollen percentages. However, the pollen influx is more obvious in representing the vegetation and environment changes. |
