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.

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In the Mochimune area, there are 51 mandarin orange orchardists, and the total area of the orchards is 10.2 ha (1970). In the Osada district including the Mochimune area, the beginning of cultivation of this fruit is, in general, pretty old. But as for the Mochimune area alone, in spite of good physical condition for cultivation, mandarin orange has been cultivated only for these 20∼25 years.
In this paper, the author studied the reasons why the Mochimune area was late in starting cultivation of this fruit.
In the Mochimune area, the fishery had been the main occupation for the people before the World War II, and the conditions were unfavourable, for the cultivation of mandarin orange, and the necessity for the cultivation of this fruit was small.
During the war the fishery was halted, and it could not be restored after the war, due to lack of ships and the other fishing facilities.
For the factors above mentioned, the cultivation of mandarin orange, instead of fishery, was introduced to the Mochimune area ofter the World War II.

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The writer has studied the development and the present conditions of the small hydroelectric plants along the Shiba River flowing south at the foot of Mt. Fuji. The results of this study are as follows.
1) There are 21 small hydroelectric plants along the Shiba River (Fig. 4), but their facilities are old and supply only a part of demand of electricity for the electric light and industrial power in this region. However, their cost of electricity production is low because the repayment of facilities has already ended. In addition, they are maintained as the urgent electricity in case of troubles of the long-distance transmission lines to this region from the hydroelectric or thermalelectric plants in other regions.
2) The first hydroelectric plant along the Shiba River was the Inogashira Hydroelectric Plant built in 1910. The completion of this plant was the one step to the modern hydroelectricity production in the Shizuoka Prefecture. The reason why the hydroelectric plant was built first along the Shiba River in the Shizuoka Prefecture was that there were a lot of sites for hydroelectricity production and the developing paper and pulp industry at the southern foot of Mt. Fuji demanded much electricity.
3) Four electric companies competed sharply for the production and supply of hydroelectricity along the Shiba River and the Fujisuiden Company held a dominant position. But, after all most hydroectric plants belonged to the Tokyo Electric Power Company which supplied electricity to Tokyo and amalagmated the Fujisuiden Company.
4) All the hydroelectric plants along the Shiba River whose capacities are from 250 KW to 4, 000 KW are conduit type. About 70 per cent of the 590-meter water head from the highest plant to the lowest one is used for genera-tion (Fig. 5).
5) The area of the Shiba River was early reclaimed as the agricultural land and at present the water rights for both irrigation and electric generation are much complicated (Fig. 8). The hydroelectric plants obtained the water rights for electric generation by paying various compensations, but the electricity production by a lot of plants decreased to a degree during the period of irrigation to the paddy fields from May to July, because irrigation rights take precedence. This kind of reduction of electricity production is far larger than the seasonal reduction (Fig. 6).

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