The Climatic Environmental Changes Since Holocene In Changbai Mountains

The past is the key to understanding the present and the future. In order to discuss the climatic environmental changes of present, research on past environmental changes are needed. These findings will lead to predict the environmental features in the future and their effects. Holocene is associated with the human evolution and civilization formation. Therefore, the research on environmental change of Holocene is the way to reconstruct the past global changes and the way to predict the climate of future. The climatic changes over this period are paid more attention, and the research of Holocene climatic changes has great significance.The natural ecological system of Changbai Mountains in northeastern China has been well preserved. It is a key spot that links the Loess Plateau and the Japan Sea in latitude direction, and also connected Russian Far East Siberia and Taiwan. The Changbai Mountains are located at a representative climatic zone in China. The changes of ancient climate and environment in this region are sure to affect the global climate, such as the E/N phenomenon and the evolution of the monsoonal evlution. Therefore, research on this special area is of great significance.Through the analysis of the sediment particle size, geochemical elements, and pollen, we can reconstruct the evolution of ancient environment since the Quaternary. This method is commonly used in the research on the ancient loess in North China. But less used for the ancient environmental evolution in Northeast of China. This paper deals with the selected sediment profile from the northern slope at different altitude in Changbai Mountains, analyzes the relative indicators ( particle size, geochemical elements, pollen). And according to the 14 C determination and the sediment profile characteristics, we try to reconstruct the ancient environment of Changbai Mountains. This multi-indicators-combined method is a new attempt for the research on ancient environment.Through comprehensive analysis of the environmental indexes, combining with the original research data, we divided the environmental evolution into 9 stages (from 10300aB.P to the present) which are as follows: 1. About 10300 9800 a B.P.Pollen analysis shows that the vegetations are mainly hardy broad-leaved forest during this period. But before 9800a, the warm liked broad-leaved species increase sharply, and the area is covered with broad-leaved forest such as elm and cen. Within the hundreds of years, the area is soon occupied by the broad-leaved forest. The vegetation evolution proves that the climate soon become warmer.2. About 9800 8300 a B.P.The vegetation during this period is similar to spring-elm and ash deciduous broad-leaved forest in the mountains of northeast China. It is presumed that the climate at that time was very close to that today. Various factors considered, it can be concluded that the temperature in that region increased obviously, but the humidity could be reduced, and aridity increased.3. About 8300 4000 a B.P.Broad-leaved vegetation of warm temperature increased during the warm period of the Holocene. In the warm period, Temperate zone species is appeared and shows that the climate is warmer than that during the last period. However, the climate becomes cold after about 5000a.4. About 4000 2300 a B.P.In the end of the warm period, the climate gradually becomes cold and wet, which corresponds to a global Holocene cooling period. However, the range of cooling was not too big.5. About 2300 1000 a B.P.Following the last stage of cold weather, pollen analysis shows that the temperature declined again. This cold event is in agreement to the Holocene low-temperature period in the northern hemisphere.6. About 1000 686 a B.P.Characteristics of particle size of sediment indicate that the water power was strong, and pollen data indicates that the vegetation during this period was a mixed-broad band. Both particle size and pollen data show that the climate was cooler. The climate was wet and cool during this period according to comprehensive analysis of the environmental indexes.7. About 686 447 a B.P.The analysis of environmental indexes revealed that the climate was mainly dry and warm.8. About 447 325 a B.P.The analysis of environmental indicators revealed that the period was mainly cool and wet.9. About 325 a B.P. so farEnvironmental indicators reflect that the climate of this period was warm and dry, and this is in line with the global warming in recent years. Besides, we first measure out the following heights: ancient timberline height (H), modern timberline height(H₁), modern vegetation height according to the ancient vegetation height at sample spot (H₂ ), and the height of the sample spot (H₃), Then with the relationship of the four heights(H=H₁-H₂+H₃), and also with the result of pollen analysis and the time determination, we attempt to resume the change of timberline from the Helene and also draw a timberline change trend graph. The result shows that the climatic change( warm or cold, dry or wet ) dramatically affects the timberline, the change range of different periods still varies. In this way we work out the timberline of the northwest slope and the western slope with a deference of only 100m, and the figure is in good accordance with the present.The results provide a good reference for the reconstruction of ancient climate in Changbai Mountains, or the whole northeast regions. It surely gives a conclusive evidence to predict the future climate evolution.