Albizia kalkora (Leguminosae subfam. Mimosoideae) is a deciduous tree distributed in Japan, China, Korea, and other countries from Southeast Asia to India. In Japan, its distribution is restricted to the evergreen broadleaved forest zone in southern Kyushu, whereas it is widely distributed in the deciduous broadleaved forest zone in China. Fossil records of A. kalkora from the Plio-Pleistocene have been limited in Kyushu, although A. miokalkora, a closely related fossil taxon, from the Miocene has been found in China, Korea, and Japan. We describe herein A. kalkora leaflet fossils from the Lower Pleistocene Sayama Formation and Middle Pleistocene Shoudai Formation in central Japan. We compared the leaflets with those of modern species in China with similar morphology and identified them as those of A. kalkora based on their size (2–3 cm long), the medial and base asymmetry, and the presence of 2–3 slender secondary veins diverging at the base. Their association with evergreen broadleaved trees in fossil assemblages indicates that A. kalkora expanded its distribution to central Japan during stages with warm winter temperatures. Its distribution was limited to southern Kyushu during the Late Quaternary in Japan, whereas in China it expanded widely into the deciduous broadleaved forest zone, possibly by adapting to cold winter conditions during glacial stages.

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The impact of the Towada-Chuseri Tephra fall (7 cm thick; To-Cu; ~6000 cal yr BP) on vegetation was investigated by the pollen analysis of core samples obtained from Tashiro Mire (560–575 m a.s.l.), Aomori Prefecture, Japan. The results indicate that a stable Fagus-Quercus forest had been established before the tephra fall. Just after the tephra fall, Quercus subgen. Lepidobalanus percentages increased abruptly by more than 80%. Other tree pollens uniformally decreased, especially Fagus, which showed a significant decrease from 30% to 2.6%. Lepidobalanus subsequently showed a gradual decline beginning 1.7 cm above the tephra, whereas other trees showed gradual increases. At 8.9 cm above the tephra (150–250 years after the tephra fall), the arboreal pollen composition reached a stable state with a similar composition to that before the tephra fall. Contrasting responses of Fagus and Lepidobalanus after the tephra fall shows their tolerances for its impact. The non-arboreal pollen composition, mainly originating from mire vegetation, also changed appreciably after the tephra fall and did not returned to the initial state, indicating that the mire condition was seriously altered.

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With the progress of the investigation on impression seeds and fruits in earthenware vessels, it has came to be discovered that impressions of Zanthoxylum ailanthoides occur particularly in the Jomon period of the Kyushu region. Although Zanthoxylum ailanthoides is now scarcely used, their synanthropic occurrences in archaeological excavations and their abundance in archaeological plant remains indicate their fruits were used for some purposes by the people in those periods, besides indicating their existence in the laurel forest characterictic in western Japan in those periods. In order to clarify their use, we analyzed the chemical constituents of the fruits of Zanthoxylum ailanthoides and allied species. Because Zanthoxylum ailanthoides fruits much include 1,8-cineole, a terpene of the essential oil toxic and repellent against some stored-product beetles, we indicated that these fruits were possibily used as an insecticide against maize weevils, Sitophilus zeamais Motschulsky, whose impressions have been discovered on the earthenware at many Jomon sites.

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Based on AMS 14C dating, re-identification of plant macrofossil, and pollen analysis of samples that were collected at Shirotsuki-Takatsu, Ooda, Shimane Pref. (200 m a.s.l.) by Dr. Shigeru Miki, paleovegetation in the last glacial maximum (LGM) in the northeastern Chugoku District, southwestern Japan, was reconstructed. A coniferous forest dominated by Tsuga diversifolia and Picea jezoensis var. hondoensis with Abies veitchii, Pinus koraiensis, Picea sect. Picea and Chamaecyparis obtusa was distributed in a valley in Shirotsuki-Takatsu during the LGM. According to the earlier studies, temperate coniferous forest was reconstructed as the most dominant forest biome during the LGM in low altitude areas along the Sea of Japan in the Chugoku District. Besides, the present fossil record indicates that a subarctic coniferous forest common with that of the present subalpine zone in central Japan was distributed in low altitude areas. A review of last glacial maximum pollen profiles from the Chugoku District showeded that vegetation was affected by geomorphology surrounding research sites rather than by altitudinal gradient, and subalpine trees dominated often in areas at lower altitudes surrounded by slopes, and temperate broadleaved trees occurred commonly in areas at higher altitudes surrounded by wetland and gentle slopes. Our research demonstrates that a re-investigation of plant macrofossil collections stored in museums enables detailed paleovegetation reconstruction with high resolution dating.

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