QUANTITATIVE ANALYSIS ON THE MAIN SUBMERGED COMMUNITIES IN HONGHU LAKE.Ⅲ.CERATOPHYLLUM DEMERSUM+POTAMOGETON CRISPUS+MYRIOPHYLLUM SPICATUM COMMUNITY

Ceralophyllum demersum + Potamogeton crispus + Mriophyllum spicatum cotnmunity had the highest seasonal maximum biomass among all the submerged vegetation types in Honghu Lake.This community showed a large difference in different stands.This complicated the species composition, C. demersum and P.crispus became dominant altematively in different seasons.Water flow played a main role in determining the horizontal distribution pattern of popuations.The vegetation cover decreased from water surface to bottom.No significant association was found between different species pairs, but significant correlation was detected between the biomass of some species pairs owing to the effect of water flow and the scatter ways of their vegetative propagation.