Multi-Proxy Evidence for Late Holocene Environmental Changes at Mt. Jeombong, Eastern South Korea

Abstract

To understand the present condition and to predict future change, past environmental change has to be studied. Information of the past environmental change is important for predicting oncoming changes. As the concern for future climate change increases, research for when and why climate change occurred and how the environment reacted during the Holocene is getting more attention. Generation and analysis of proxy data covering the Holocene is thus very important in order to better understand the current climate and environmental change.

The purpose of this research is to analyze multi-proxy data from a wetland on Mt. Jeombong to reconstruct Late Holocene climate and environmental changes. Radiocarbon dating, water & organic content, magnetic susceptibility, grain-size analysis, carbon isotope analysis, pollen analysis and charcoal analysis were carried out from two sediment cores (21 ~ 93 cm and 18 ~ 98 cm) for the research. The results are as follow. First, the sediment was dated to 940±40 yr BP (1095±50 AD) and according to the pollen analysis, sediment was divided into 4 zones. The climate and environment of zone 1 which is oldest changed from a humid climate and suitable environment for herbaceous plants to a suitable environment for woody plants. Quercus was dominant and Fraxinus also showed a high appearance ratio which indicated a warm period. However, Pinus started to increase and Quercus decreased as time passed which indicates the climate was getting cooler. Other proxy data showed decreasing precipitation level which indicates the climate change from humid to dry. In zone 2, Pinus showed its highest ratio with increasing Abies while Carpinus and Fraxinus decreased. This was the coldest period out of all the pollen zones. Grain-size was finest and magnetic susceptibility was at its lowest which indicates a dry period. In zone 3, there was a sudden change in the proxy data. This was not caused by climate or environmental change but caused by human activity. The results of proxy data, especially charcoal, indicates a disturbed environment. According to the historical documents, this period was characterized by continuing coldness and drought. Furthermore, corrupt bureaucrats impoverished life of commoners which caused many revolts all over the nation. For these reasons, commoners moved into deep mountains and started slash-and-burn farming in order to survive difficult times. Zone 4 is characterized with a high appearance ratio of herbaceous plants and returning woody plants. This shows a typical post-disturbed environment.

Second, the Koreas Medieval Warm Period and Little Ice Age were compared with the results of proxy records. Warm and humid zone 1 matched with the MWP, relatively cooler and drier zone 2 & 3 matched with the LIA, and zone 4 which was getting warmer again could be viewed as post-LIA period.

This research reconstructed the Late Holocene climate and environmental changes from a well preserved wetland using proxy data. Also, this research studied Koreas MWP and LIA which still need more information and research.