渓流の瀬における極相の底生動物群集の季節変動および年次変動

抄録

The seasonal and the annual changes of benthic communities of the climax in rapids were studied at Heiwabashi station in the middle reaches of the Taru River, during the years from 1968 to 1974. The Taru River, about 18 km in length, is situated in Nagano Prefecture, Central Japan. The River has clean water and a stable environment. A net-spinning caddis-worm Stenopsyche griseipennis was always dominant. But the next dominant species changed with each season and year by year. The benthic communities were composed of 18 to 27 species per 0.25 m^2 (50 cm×50 cm), and the maximum number of species was in early spring. The individual number increased in summer. The standing crops were 3.9 g to 23.5 g in wet samples per 0.5 m^2,the maximum being in spring and the minimum at the end of autumn. The diversity index was at the minimum in summer and at the maximum in early spring. The annual changes in the number of species, individual numbers and standing crops of the benthic communities were relatively small. But each species except the dominant species had noticeable annual changes in the individual numbers and standing crops.