Characteristics and distribution causation of aquatic macrophytes in Guohe River of East China

On the basis of field survey and laboratory measurement,and by using Two-Way Indicator Species Analysis(TWINSPAN) and CCA ordination,this paper studied the species composition and community type of aquatic macrophytes in the Guohe River of Huaihe River Basin,and approached the key environmental elements affecting the distribution of the macrophytes.A total of 27 aquatic macrophyte species belonging to 20 families and 23 genera were recorded,of which,submerged and emergent species were the dominant species,accounting for 74% of the total.The macrophytes could be classified into 8 community types,i.e.,Form.Eleocharis congesta + Scirpus trigueter,Form.S.trigueter + Alternanthera philoxeroides,Form.S.trigueter,Form.Ceratophyllum demersum,Form.A.philoxeroides,Form.Phragmites australis + A.philoxeroides,Form.Nymphoides peltatum,and Form.Trapa bispinosa + Nuphar pumilum.There existed greater variations in the environmental factors,especially the concentrations of NH4+-N,NO3--N,and total P in water body and the water depth,among the 8 community types.The CCA ordination showed that the physical and chemical characteristics of water body,such as the NO3--N,PO4-and total P concentrations,were the key factors determining the distribution of aquatic macrophytes in the Guohe River.