A vegetational reconstruction and a dendrochronological application were carried out on a subfossil forest (approx.13,000yrs BP) buried by the Hachinohe tephra from the Towada Volcano at Ikenai, Ohdate city, Akita Prefecture, northern Japan. The subfossil forest is located at the southwest of the Towada Volcano and is covered with the pyroclastic flow deposits of the Towada-Hachinohe tephra (To- H) without the pyroclastic fall deposits (To- HP). Subfossil woods show establishment of a Picea forest accompanied with Abies in the Last Glacial Age. The forest trees were studied dendrochronologically to clarify the burial process. In the forest, five well preserved discs were obtained from lying trunks of Picea, and their tree-ring widths were measured and correlated. Cross-dating succeeded among the individuals, and three trees were found to die in the same year. In the previous work at the east slopes of the Towada Volcano, we made a standard tree-ring index (STD) of Picea in subfossil forests under the Towada-Hachinohe tephra. Cross-dating succeeded between three individuals of this study and STD which revealed that the terminal rings were formed in the same year. Further observation on the terminal rings showed that their latewood formation had already ceased before death, agreeing with the result of the previous work. Thus Towada Volcano erupted in winter and the eastern and the southwestern forests were buried by the Hachinohe tephra and died out in the same season.
Late Pliocene plant macrofossil assemblages on Awaji Island, central Japan, were studied to reconstruct the habitat of plants and to complement the upper Pliocene biostratigraphy of the Osaka Group. The lower part of the Atago Formation yields many plants extinct from Japan and includes Choerospondias axillaris and Reevesia sp. that characterize the basal part of the Osaka Group in the Sennan area. Stratigraphic occurrence of plant fossils in the upper Pliocene on Awaji Island is very similar to that in the Sennan area. Sedimentary facies of fossil bearing beds were classified into three types, i.e., peat, massive silt, and stratified sand, and occurrence of plant taxa was compared between these types to reconstruct their habitat. Glyptostrobus pensilis, Trapa and Nymphaeaceae included in peat were growing in backmarshes in an alluvial plain. Plants common in massive silt, such as Metasequoia glyptostroboides, Stewartia monadelpha, Sequoia sp., and Pseudolarix amabilis, composed forests in wetlands and on sandbanks in an alluvial plain. Plants common in stratified sand, such as Picea sect. Picea, Buxus microphylla, and Fagus microcarpa, grew on fans and mountain slopes around a sedimentary basin.
The Yoshinogari Site in northern Kyushu was one of the nuclear sites of the Yayoi Period and continued up to the Middle Age. Wooden artefacts recovered at this site, mainly of the Middle and Late Yayoi and Nara Periods, included ca. 50 taxa. Species selection for 660 wooden artefacts shows that as many as 44 taxa were selected more or less equally during the Yayoi Period, whereas Abies was used, among 28 taxa, for half of the artefacts in the Nara Period. For building and construction timber, Castanea crenata was preferred for foundation timber and posts but with 18 other taxa during the Yayoi Period, whereas Abies was used nearly exclusively for well members and flat grain boards and Castanea creanata for posts together with eight other taxa in the Nara Period. For other artefacts, Quercus subgen. Cyclobalanopsis for cultivation and manufacturing tools of both periods and Abies for magemono containers of the Nara Period are conspicuous. Usage of Apho,nanthe aspera, Celtis, and Marus during the Yayoi Period and their obscurity in the Nara Period in spite of continued usage of evergreen laurel forest elements agree with vegetation changes reconstructed from pollen and plant macrofossil assemblages at this site.