Uncarbonized fruits of Castanea crenata were collected from 14 archaeological sites since ca. 10000 yBP, in Japan. In the Earliest Jomon Period (ca. 9300 yBP), the fruit size was similar to the wild ones. During Early to Middle J omon Period, (ca. 6000 to 4000 yBP), their size became larger. In the Late to Latest Jomon Period (ca. 4000 to 2250 yBP), some of them are twice larger than the wild ones, and reach the size of the modern cultivated forms.
We described the stratigraphy, wood fossil, plant macrofossil, and pollen fossil assemblages of the wood peat bed with buried stumps in the southern part of the Yogo lowland along the Yanagase fault, and reconstracted a vegetation in and around the lowland based on the plant fossil assemblages. The wood peat was deposited during the late Holocene from ca. 4500 to 3500 years ago, based on radiocarbon dating. It was suggested that the Alnus japonica-Fraxinus mandshurica var. japonica forest stood in the central part of lowland, and the forest vegetation composed of many coniferous and broadleaved species such as Cryptomeria, Aesculus, Carpinus tshonoskii, Cephalotaxus harringtonia, Quercus serrata, Castanopsis, and Quercus subgen. Cyclobalanopsis, distributed in the surrounding area. The finding of Fraxinus mandshurica var. japonica in the Y ogo lowland suggested cooler climate than at present and a formation of wood peat related to such climatic condition. An expansion of lake area occurred due to the activities of the Yanagase fault might led caused a disappearance of forest in the central part of lowland at ca. 3500 years ago.
Transportation and preservation of phytoliths were discussed, based on a relationship between the distribution and weathering degree of phytoliths in surface sediments and that of mother plant, in the estuary of the Obitsu River along the Tokyo Bay. Nine types of phytoliths obtained from surface sediments were identified : Carex pumila, Ischaemum anthephoroides, Calamagrostis epigeios, Phragmites australis, Carex scabrifolia, Lolium perenne, Imperata cylindrica var. koeni'gii, Bromus unioloides, and Phacelurus latifolius types. The distribution pattern showed that the first 5 types had a characteristics efficient transportation, and that the rest to be less efficient. It was suggested that most of phytoliths were transported by wind after a disintegration of leaves, to low places such as break of slope points and salt pond, and with silt and very fine sand particles of sediments.