瓶ヶ森氷見二千石原における過去700年間の植生景観と人間活動

抄録

A 700-year landscape history of Himi-nisengoku-hara, a 40-ha dwarf bamboo-dominated area with Nikko fir (Abies homolepis Sieb. et Zucc.) trees, located near the 1896-m peak of Mt. Kamegamori, was revealed mainly by paleoecological analyses. Pollen and charcoal analyses were done for four sediment cores from small hollows in the dwarf-bamboo thicket. Also, the relationship between the modern pollen assemblage and vegetation was examined by using pollen surface samples collected from the dwarf bamboo thicket and Nikko fir stands. Ratios of Gramineae to Abies pollen (G:A) were useful for differentiating the dwarf bamboo thicket and fir stand pollen assemblages. A feature of all pollen assemblages from the four sediment cores was a high percentage of Gramineae pollen. The G:A ratios of fossil pollen indicated that Himi- nisengoku-hara had open landscapes during the past 700 years. Tree census data and tree-ring cores obtained from three plots suggested that Nikko fir trees were established in the periphery of Himi-nisengoku-hara at least 250 years ago, and invaded to the center of the area in synchrony with the simultaneous death of the dwarf bamboo at AD 1964. The increase of charcoal fragments with buckwheat pollen ca. 300 years ago may have been due to slash-and-burn cultivation around the area.