Pollen-based reconstructions of Japanese biomes at 0, 6000 and 18,000 C-14yr BP

A biomization method, which objectively assigns individual pollen assemblag es to biomes (Prentice et al., 1996), was tested using modern pollen data f rom Japan and applied to fossil pollen data to reconstruct palaeovegetation patterns 6000 and 18,000 C-14 yr BP Biomization started with the assignmen t of 135 pollen taxa to plant functional types (PFTs), and nine possible bi omes were defined by specific combinations of PFTs. Biomes were correctly assigned to 54% of the 94 modern sites. Incorrect ass ignments occur near the altitudinal limits of individual biomes, where poll en transport from lower altitudes blurs the local pollen signals or continu ous changes in species composition characterizes the range limits of biomes . As a result, the reconstructed changes in the altitudinal limits of biome s at 6000 and 18,000 C-14 yr BP are likely to be conservative estimates of the actual changes. The biome distribution at 6000 C-14 yr BP was rather similar to today, sugg esting that changes in the bioclimate of Japan have been small since the mi d-Holocene. At 18,000 C-14 yr BP the Japanese lowlands were covered by taiga and cool m ixed forests. The southward expansion of these forests and the absence of b roadleaved evergreen/warm mixed forests reflect a pronounced year-round coo ling.