Surface pollen investigation in the warm-temperate to subtropical regions of Japan : an attempt for quantitative palaeoclimate reconstruction on Quaternary interglacials

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The pollen-based modern analogue technique (MAT) can provide constraints for climate projections for the next decades (IPCC, etc) by reconstructing quantitative palaeotemperature of human habitation areas during the late Quaternary. However, a so-called fade-out problem of reconstructed temperature in >16℃ regime has prevented the MAT from providing analogues for the >2℃ warmer world than present. To reduce this problem, we perform surface pollen investigation for warm-temperate to subtropical regions of Japan, of which annual mean temperature exceeds 16℃.In geographical context, southern Kii peninsula, SW Shikoku, Kyusyu and islands of Tanega-shima, Amami-Oshima, Okinawa, Hachijo-jima, etc are selected for hot region up to 23℃. The collected samples (surface pollen materials composed of living moss polster) are analyzed in the standard palynological procedure to fill the gaps in the >16℃ regime of Japan. Results provide a complete temperature curve without lack in extreme temperature … More zones (5-7℃ warmer than the present in the Kinki-Kanto districts).In palynological context, almost all the lower warm-temperate to subtropical zones, located to the south of Shikoku, are dominated by abundant Castanopsis pollen. High values of evergreen oak (Cyclobalanopsis) are restricted in the upper warm-temperate zone (<16℃ in annual mean temperature). In addition, an attempt of palaeoclimate reconstruction using previous surface pollen is also performed on the fossil pollen record from Lake Biwa. These results have been summarized into two English manuscripts for international journals (Okuda et al., Tarasov et al.).We note that this project also deal with the surface pollen investigation for ocean floors around the Japanese archipelago. The NW Pacific has had a lot of ocean coring points. Since the cored materials from the marine realm are preserved in JAMSTEC, San-So-Ken, etc, sabsampling and analyzing muddy sediments from the core tops can provide surface pollen dataset beneath the ocean, which is in the same manner as those in terrestrial regions.Unfortunately, surface pollen samples themselves cannot be collected in current urban areas around e.g. the Tokyo Bay. To reduce this problem, we performed a borehole core project in central Chiba city. Results show that fossil pollen of 1500-2500 yr BP age, with little vegetation disturbance by early humans, can serve as a substitute for modern surface pollen. Less