水田における施肥とプランクトン群集の種組成の関係

抄録

Seasonal changes of numbers and species composition of phyto- and zoo-plankters in fertilized and non-fertilized paddy fields were surveyed from June to September of 1982 at Saitama Agricultural Experiment Station, Kumagaya, Saitama Prefecture. Both fields have been irrigated with a small channel from the River Arakawa, and experiments on the effects of fertilizers on the growth of rice plants have been made since 1944. The former field was fertilized with about 12 g N and 4 g P m^-2 in June, whereas the latter was not. In any sampling, concentrations of NH₄-N and PO₄-P, and numbers of phyto- and zoo-plankters were higher in the fertilized field than the non-fertilized one. The following sequence of the dominant groups was recognized in the non- fertilized field : Bacillariophyceae - Cyanophyceae - Bacillariophyceae Cyanophyceae ; in the fertilized one, the sequence was Bacillariophyceae - Cyanophyceae - Chlorophyceae - Chlorophyceae Bacillariophyceae - Bacillariophyceae. The latter was characterized by the appearance of Chlorophyceae (mainly Scenedesmus sp.) in summer. Seasonal changes of the dominant zooplankters are no difference between the two fields and were divided into the following three periods : Protozoa, Crustacea and Rotifera period.