Based on the field studies in Yilan county in the Northwestern Sanjiang Plain,the diversity of plants in some waters of rivers Mudan,Weiken and Balan were measured.The results show:βdiversity is high in Mudan River,lower in Balan River and lowest in Weiken River.In the hierarchies of botanical classfication,the βdiversity of species level is higher than those of genus and family levels.The diversity is higher in riverplain ecotone than in others.The diversity is lower in the high elevation above and ...