11:45 AM - 12:00 PM
[HQR05-11] A natural disaster can be a factor of landscape change? – with special reference to Lake Kitagata in Awara, Fukui, Japan
Keywords:pollen analysis, vegetation, disaster
Based on the pollen analysis, the land including plain area were covered with dense forests of evergreen oak and Castanopsis. Salt making caused a deforestation in plain area and around the 12th century when land transformation to agriculture occurred, paddy fields seems to be developed in the deforested area for salt making around Lake Kitagata. Buckwheat has been cultivated intensively since the late 13th century AD when the Little Ice Age started in Japan. The development of pine forests dates back to around the 17th Century AD. Before this, the area was spotted with few trees especially in plains and ferns grew thickly in the river mouth of Daishoji River. It seems that the surrounding vegetations have transformed to Japanese cedar and evergreen forests recently.
During this succession, natural disasters seemed to change the vegetation. One may be in response to Tensho Tsunami in 1586. Almost all pollen taxa decreased but Pinus subgen. Diploxylon. In this time, salt damage might not happen since Chenopodiaceae which has salt tolerance did not increase. Another one was observed in the late 17th century AD. It seems that the vegetation was damaged by salt. Large amount of Chenopodiaceae pollen was observed in this period. A peasant uprising which was caused by crop failures due to salt damege and typhoon was recorded in AD1712. However, the vegetation was soon recovered. Although an impact from disasters on vegetation was observed, it did not last long. Human activities and climate seems to be much bigger factors.