Japanese Journal of Historical Botany

We reconstructed vegetation changes from a well-dated pollen record since the early Holocene at Manjojiki Mire (660 m a. s. l.) in southern Hokkaido to understand the vegetation history on Kameda Peninsula. The pollen record at the mire indicated that, 1) in ca. 10.0 ka cal BP, a mixed forest of Betula ermanii and boreal conifers surrounded the mire in a cool climate, 2) in ca. 9.5–6.8 ka cal BP, a Betula ermanii dominant forest expanded in a warm climate, 3) in ca. 6.8–1.1 ka cal BP, a Quercus crispula dominant forest developed, and 4) after ca. 1.1 ka cal BP, a Fagus crenata forest flourished around the mire. Additionally, our spatio-temporal comparison of pollen records on Kameda Peninsula showed that boreal coniferous forests consisting mainly of Picea and Abies existed during ca. 15.0–12.0 ka cal BP, that mixed forests of Betula and Quercus developed during ca. 12.0–3.0 ka cal BP, and that Fagus crenata forests flourished after ca. 3.0–1.0 ka cal BP. The results implied that the colonization by Fagus crenata of the peninsula began in ca. 6.0–5.5 ka cal BP, possibly enabled by the sedimentation of tephra from Mt. Komagatake volcano.

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In Ibaraki Prefecture, a buried forest of the late Jomon period was excavated at the Jinyashiki-teishicchi site in the late 1980s. Although plant phytoliths, pollen fossils, and plant macrofossils were already reported, fossil woods have not been reported, and no radiocarbon dating was done. To examine vegetation change around the site, we carried out radiocarbon dating, pollen analysis, and diatom analysis of preserved sediment samples and report their results with that of fossil woods. On the upland around the site, deciduous forests of Quercus subgen. Lepidobalanus spread from the early phase of the late to the early phase of the final Jomon periods, and were replaced by evergreen forests of Castanopsis and Q. subgen. Cyclobalanopsis in the middle Yayoi period. In the valley, a layer of pot sherds and burnt soil was formed during the early to middle phases of the late Jomon period, and Fraxinus grew along the stream, and Castanea stands were maintained on the surrounding slopes. During the late phase of the late to the early phase of the final Jomon periods, a forest of Fraxinus and Q. subgen. Cyclobalanopsis grew on the layer of pot sherds and burnt soil with less human activities around the site.

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