PHYTOCOENOLOGICAL STUDIES ON FLOATING-LEAVED ANCHORED AQUATIC PLANTS IN FUTOUHU LAKE,HUBEI I.THE STRUCTURE OF COMM TRAPA SPP.

The structure of Comm Trapa spp.was investigated in Futouhu Lake in Hu-bei. The coinmunity is rich in species and composed of 15 species of plants,amongwhich 5 life forms and 13 growth forms are noted.Analyses of the life and growthforms reveals a clear pattern in the structure of species composition in Comm.Trapa spp.The community exhibits characteristics of zonation and patchy distribution. Populations of Trapa spp.are contagious,varying from 0.16m2 to 8m2 in spatialdistributions.The accompanied hydrophytes also show patterns of zonation andpatchy distribution.Furthermore,the vertical structure of the community consistsof only two layers:the floating-leaved hydrophyte layer and the submerged hydro-phyte layer.However,almost all of the photosyntliesis system and most biomass ofthe floating-leaved aquatic phytocoenoses were concentrated on the layer of watersurface, while advanced root or rhizome svstem was not observed below the substr-ate. Populations of Trapa spp.reached peaks in standing crop and in sexual repro-duction in June and July. Populations of Nymphoidcs peltata and Hydrocharisdubia,which overlap partly with Trapa spp.in spatial niche,showed segregationin temporal niche.