Annual and Seasonal Variations in Biomass of a Floating—leaved Plant, Trapa natans L., in Takahamairi Bay of Lake Kasumigaura, Japan

Abstract

Seasonal patterns of vegetative growth of Trapa natans L. in Takahamairi Bay of Lake Kasumigaura were investigated in 1978, 1979, 1980, 1981 and 1984. Maximum biomass was approximately 300g dry weight m–2 in normal years, and a proportion of leaf biomass was as large as 45%. Seasonal patterns of biomass change were considerably variable among years; only one peak biomass was observed in 1978, 1981 and 1984, while two peaks were noted in 1979 and 1980. Overcrowding of rosettes in early summer due to high spring temperature would be the main reason for the subsequent summer collapses of the biomass observed in 1979 and 1980. © 1987, The Japanese Society of Limnology. All rights reserved.