Japanese Journal of Historical Botany

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Based on pollen analysis and tephra determination, vegetation changes since MIS 15 were reconstructed using the upper 75 m of a 120 m-long sediment core (UT core) from the Uwa Basin, southwestern Shikoku, Japan. We recognized 43 local pollen zones, UT-1 to UT-43, in a descending order and compared these pollen zones with the LR04 marine isotope stack. Chronology was based on widespread tephra layers, AT, Aso-4, Ata, Aso- 3, Aso-2, Ata-Th, Kkt, Oda, Hwk, and Yfg. Pollen zones corresponded to marine isotope stages as follows: UT-3 to UT-5 to early MIS 3 to final MIS 5; UT-6 to MIS 5.1; UT-8 to the last stage of MIS 6; UT-9 to UT-15 to MIS 6; UT-16 to the boundary of MIS 6/MIS 7; UT-17 to UT-22a to MIS 7; UT-22b to UT-24 to MIS 8; UT-25 to UT- 29 to MIS 9; UT-30 to early MIS 9; UT-31 and UT-32 to MIS 10; UT-33 to MIS 12; UT-34 to UT-43 to MIS 15. During glacial periods, MIS 12, MIS10, MIS 8, MIS 6, and MIS 3-4, forests were dominated by Picea and/or cooltemperate broad-leaf trees such as Fagus, Quercus subgen. Lepidobalanus, and Carpius. MIS 8 was the moistest glacial period during the last 300,000 years. During interglacial periods, MIS 9, MIS 7, and late MIS 5, forests were composed mainly of Cryptomeria japonica.

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Our spatial reconstruction of vegetation (from the fossil pollen and wood profiles of two peat layers) spanning the Last Termination on Mt. Chokai, northeastern Japan, advanced our understanding of vegetation history on the Japan Sea coast. Both types of remains indicated: 1) in ca. 14–11 ka cal BP, deciduous broad-leaved scrubs mainly consisting of Betula ermanii, Acer tschonoskii, and Alnus firma existed at 700 m a.s.l.; 2) after ca. 14 ka cal BP, boreal conifers disappeared from this area, probably due to warming of the Last Termination. Furthermore, we identified a fossil wood of Larix, probably L. gmelinii, from the peat layer of ca. 14–11 ka cal BP. This discovery implies that L. gmelinii expanded its distribution into peat bogs on the Japan Sea coast in the final stage of its extinction process, little affectd by snow accumulation in winter.

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