Abstract
In spite of an intensive work of nearly thirty years, no satisfying explanation is given for the existence/nonexistence of tundra and/or forest tundra in eastern and northern Hokkaido during the last glacial maximum. To supply basis for the reconstruction of past vegetation in this area, pollen transfer and deposition were examined in a mire on Yururi Island, a small, unforested island 3 km off the Nemuro peninsula. Modern pollen assemblages obtained from Sphagnum-polsters were compared with the surrounding vegetation. On average, 34.8 (19.7–54.5)% of pollen and fern spores were thought to be derived from outside the island, and tree pollen accounted for 90% of such transported pollen. An average of 20% of tree pollen was transported from the south, such as southern Hokkaido or Honshu and were mainly derived from Pinus subgen. Diploxylon and Cryptomeria. Pollen is carried to Yururi Island mainly by the summer monsoon and is deposited there. When sampling is made in a large unforested area, long-distance pollen is supplied from an extensive area and affects pollen spectra. If percentages of pollen transported over long distances and those of non-tree pollen from a local vegetation can be estimated reasonably, past woodland can possibly be distinguished from past grassland.
