Reconstruction of the vegetation at A.D. 915 at Ohse-yachi Mire, northern Japan, from pollen, present-day vegetation and tephra data

Abstract

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 was dated from ~4C data, stratigraphy at archaeological sites and a historical record. Twelve cores along two perpendicular transects yielded pollen from modern and pre-tephra samples. The modern pollen data were compared with the modern vegetation, and used to interpret the pollen 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 became drier and changed to the present-day mixed Moliniopsis-Sphagnum bog.

Light interception in species with different functional groups coexisting in moorland plant communities

“…), and Tamoyachi (40°40 0 N, 140°52 0 E, 1,290 m a.s.l.). Pollen analyses suggested that species composition has been maintained for 1,000-2,000 years (Yonebayashi 1996(Yonebayashi , 2001Yoshida 2006). On 1 August 2005, we positioned temperature loggers (Stow Away TidbiT; Onset Computer Corporation, Bourne, MA) in the shade of shrubs, at a height of 30 cm from the ground, at each site and measured air temperature every 6 min.…”

“…Moorland is an ideal model ecosystem because its species composition is often conserved for 1,000 years (Yonebayashi 1996(Yonebayashi , 2001, and it contains many species with different functional groups, such as evergreen/deciduous and herbaceous/woody species within a small area (Mochida et al 1997). In addition, species composition often greatly varies depending on altitude and on microtopography even within a moorland (Mochida et al 1997), which enables us to obtain general trends across different species within each functional group.…”

Reconstruction of local vegetation in AD 915 at an oligotrophic mire in northern Japan from pollen, present‐day vegetation and tephra data

“…Mires in the region would reflect the changes in local environmental conditions, and it is questionable whether all the mires nearby show the same vegetational trend as indicated by the Ohse‐yachi Mire. Using an approach for small‐scale changes in local vegetation, similar to that by Yonebayashi (1996), the present study will show: (i) the aerial extent of the Shimo‐kenashi Mire and the detailed spatial pattern of its vegetation in AD 915; (ii) trends in vegetational change since AD 915; and (iii) differences in the vegetational histories of the Shimo‐kenashi and Ohse‐yachi Mires.…”

“…The B‐Tm tephra is attributed to an eruption of Mount Baegdusan on the border between China and North Korea in the 10th century (Machida et al 1981; Yamada & Inoue 1990; Machida & Arai 1992). The lower one, the To‐a tephra, which is estimated to have fallen in AD 915, is a very useful tool for determining a synchronous level (Yonebayashi 1996). Although the To‐a tephra in the study area is thinner (1–9 cm) than in the southern Hakkoda Mountains because of the longer distance from the source, it is still distinct.…”

“…The present study aims to reconstruct the aerial extent of the Shimo‐kenashi Mire in northern Japan, as well as the spatial pattern of its vegetation in AD 915. The reconstruction of past vegetation at the Ohse‐yachi Mire, approximately 7 km to the south of the Shimo‐kenashi Mire, has shown that the mire changed from a wet Sphagnum bog in AD 915 to the present drier Moliniopsis – Sphagnum bog (Yonebayashi 1996). Mires in the region would reflect the changes in local environmental conditions, and it is questionable whether all the mires nearby show the same vegetational trend as indicated by the Ohse‐yachi Mire.…”