RECONSTRUCTION OF THE VEGETATION AT AD-915 AT OHSE-YACHI MIRE, NORTHERN JAPAN, FROM POLLEN, PRESENT-DAY VEGETATION AND TEPHRA DATA

The Towada-a (To-a) Tephra from A.D. 915 allowed reconstruction of the local and regional vegetation at and near Ohse-yachi Mire from pollen samples taken just below the tephra. In earlier studies the tephra wa s dated from C-14 data, stratigraphy at archaeological sites and a his torical record. Twelve cores along two perpendicular transects yielded pollen from modern and pre-tephra samples. The modern pollen data wer e compared with the modern vegetation, and used to interpret the polle n data from A.D. 915. Ericaceae, Drosera, Sanguisorba, other Rosaceae, and Sphagnum were concluded to be local elements. Ohse-yachi Mire was a wet Sphagnum bog in A.D. 915, with Sphagnum dominating the central part of the mire. The present stand of scrub was not yet established, but there was a stand of Pinus pumila scrub. The bog subsequently beca me drier and changed to the present-day mixed Moliniopsis-Sphagnum bog .