Reconstruction of the Kamimida Site Environment in the Yayoi Period

Abstract

Ecological research on the prehistoric environment involves more than the complex of interacting physical and biological elements. It needs new perspective on the natural and cultural modifications of the environment. This paper attempts to explain some of the inter-relationships between man and his environment during the Yayoi Period (2, 300-1, 700 B.C.) by stratigraphical and palynological metheds. The site chosen for investigation is the Kamimida Site, located some 2km south of the Suzuka River in Mie Prefecture.The following environments were reconstructed;1) Geomorphic environment; During the early Yayoi Period, man lived on the flood plain of the Suzuka River, particularly selecting the dry higher area which was composed of sand and gravel and which extended from south to north around Kamimida Site. On the eastern sideof this selected area were lagoons and marshy lowlands, rich in humic soil, which were made into rice fields. In the latter half of the middle Yayoi Period, a great flood occurred and the residental area were covered with sand and gravel, but the area was resettled during the late Yayoi Period. Flood destruction interrupted the inhabited area, and consequently the living environment is a dryer than in the early middle Yayoi Period. At the close of late Yayoi Period, the geomorphic environment around the Kamimida Site changed dramatically due to further flooding, and the dwelling place of the late Yayoi Period buried by the flood destruction, presently there is a 50cm deposition stratum until 600-700 A.D. It is concluded that the flooding which formed the present micro-landform pattern is the primary factor which brought the Kamimida Site to ruin.2) Vegetational landscape; The prsent vegetation around Kamimida Site is dominated by the coppices consisted of Pinus densiflora, Quercus serrata and Cryptomeria japonica. The vegetation of Yayoi Period, however, differed greatly from the present pattern. As the result of pollen analysis of Kamimida Site clay sample, it is cleared that the broad-leaved ever-green trees, the climax vegetation in this region, predominated during the early and middle Yayoi Period. The particular pollens of Cyclobalanopsis and Shiia are the most abundant in the sediment of early and middle Yayoi Period. During the late Yayoi Period, coniferous pollens especially of Cryptomeria, Pinus and Quercus increase, while broad-leaved ever-green trees such as Cyclobalanopsis and Shiia decrease. It seems likely that these change in the tree pollen assemblage are due to the effects of man's activities upon natural vegetation. Artemisia, Compositae, Chenopodiaceae, Persicaria and Xanthium strumarium grew around the dry higher inhabited area, while Oryza sativa, Phrugmites communis, Cyperaceae, Osmunda and Polypodiaceae concentrated in the swampy lowland. From these facts, it is considered that Yayoi people lived on partly wooded landscape rather than middle of dense forest.3) Agricultural development; Cereal pollens were defined from the early Yayoi Period and seeds of cultivated plants (Oryza sativa, Cannabis sativa, Cucumis melo var. makuwa, Lagenaria leucantha) were detected. Hordeum was traced back to the early Yayoi Period. Variation in pollen grain size of Gramineae changed radically between the early and late Yayoi Periods. Gramineae of more than 40μ in diameter predominated during the early Yayoi Period, while in the late Yayoi Period, the larger Gramineae decreased and Gramineae of less than 40μ abruptly incresed. This evidence indicates that the intensification of late Yayoi agriaultural activities led to further expansion of cleared land.The reconstruction of the gemorphic, vegetation, and agricultural environment present a partial understanding of the man-land relationships existing during the Yayoi Period.