キーワード：土壌溶液，イオン分布，土壌断面形態，土壌型，微地形

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Soil Ecological Studies in Arakawa River Watershed, Saitama Prefecture, Japan (Part 1)
Soil Profile Description and Ion Vertical Distributions of the Soil Solutions
on Mountains, Hills, Uplands and Lowlands

Tadashi FUKUDA
Saitama Museum of Natural History, Nagatoro 1417-1, Nagatoro-machi, Chichibu-gun, Saitama 369-13, Japan
and
Kan-ichi SAKAGAMI
Faculty of Agriculture,Tokyo University of Agriculture and Technology, Saiwai-cho 3-5-8, Fuchu, Tokyo 183 Japan

Abstracts
　　　Nutrients circulate through plants and soils. Plants absorb nutrients generally as inorganic ions. Therefore, it is important that contents of inorganic ions in soil solutions are evaluated. Many works on nutrient cycles had been mostly investigated under being subject to the artificial influences of fertilizers or deforestations.
　　　In our studies, ion contents ( Cl, NO3,SO4,Ca,Mg ) of soil solutions were determined in natural soils of mountains, hills, uplands, and lowlands in Arakawa river watershed, and then the relationships between the patterns of ion vertical distributions and relief, vegetations and soil moisture of the sites, were discussed.
　　　As a result, the following items were clarified. Arakawa river flows in lime-stone region, and so the Ca-rich streams of Arakawa river have affected the ion contents of soil solutions, and the closer to the head of the stream the site is, the higher the Ca content of the soil solution is. Ion distributions reflect relief and vegetation, and the environmental factors form the corresponding soil type. The ion distribution pattern in the lowland is not similar to that in the other topographical sites. In alluvial lowland, many naturalized plants facilitated to alkalic soil conditions are found.