Vegetation and Climate during the Last Glacial Maximum in Japan

Abstract

AbstractThe Japanese Archipelago was almost entirely covered by coniferous forests during the last glacial maximum. Northern Hokkaido was distinguished by coniferous parkland and tundra vegetation, while southern Hokkaido and northernmost Honshu were covered by northern boreal coniferous forests consisting mainly of Picea jezoensis, Picea glehnii, Abies sachalinensis, and Larix gmelinii; Tsuga was missing from the forest. More diverse boreal forests including species from Sakhalin and northern Japan grew together in northeastern Honshu. Central Honshu and the mountains of southwestern Japan supported subalpine coniferous forests which are now mainly restricted in distribution to the central mountains. Temperate coniferous forests (Picea polita, Abies firma, and Tsuga sieboldii) existed principally in the modern mid-temperate and evergreen laurel-oak forest regions. Haploxylon pine and tree birch were also abundant in the boreal and cool-temperate zones, as was Diploxylon in the southern temperate zone. Significant populations of Fagus were found along the Pacific coasts of Kyushu and Shikoku, but they were too small to be defined as a beech forest zone. Quercetum mixtum (Quercus, Ulmus, and Tilia) was more common in the coastal lowlands of southwestern Japan than those of northeastern Honshu; it was completely eliminated from Hokkaido. The reduced mean August temperature inferred from the floral assemblages showed a latitudinal gradient 20,000 yr ago; it was 8–9°C in northern Hokkaido, 7.7–8.7°C in northernmost Honshu, 7.2–8.4°C in the central mountains, 6.5°C in the Chugoku District, and 5–6°C in Kyushu. The probable annual precipitation ranged from 1050 to 1300 mm along coasts in southwestern Japan during the culmination of the last glaciation.