Abstract:

Riparian zones are the interfaces between terrestrial and aquatic ecosystems We examined the vegetation of riparian areas in Gan River of the Poyang Lake Stream， focusing on how persistent human disturbance and riparian geomorphology influence the structure and composition of groundflora vegetation We collected data from 109 standard samples among three different disturbance types and reaches in Gan River Stream Along each samples we measured： （1） overstory basal area， species composition， and canopy closure on a series of 400 m2 plots； （2） under story species composition and canopy on a series of 36 m2 plots； （3） herb communities on a series of 1 m2 plots； （4） disturbed and physiographic data （eg longitude and latitude， elevation， gradient， river width， bank height， flow velocity）. Based on the field survey data， the communities on Gan River riparian were classified and ordinated by multivariate statistical analysis of twoway indicator species analysis （TWINSPAN） and detrended correspondence analysis （DCA）. As a result， the vegetation of Gan River riparian classified the samples into six vegetation types： riparian ruderal grasses， riparian deciduous communities， floodplain meadow， riparian broadleaved evergreen communities， riparian temperate mixed forest， Pinus massoniana communities Using correlation analysis for DCA two axis and environmental factors， the factors of gradient， height of riparian， disturbance methods， slope has the significant correlation with AX1， but the factors of elevation， gradient， slope has the significant correlation with AX2. It is suggested that soil moisture， landform and disturbance were the important factors for understanding the Gan River vegetation patterns This six vegetation types has obvious distribution pattern， rivermargin tussock， floodplain meadow and riparian deciduous communities distributed in middle and lower reaches， and other three types of vegetation distributed in upper middle valley riparian The riparian zone vegetation of Gan River is a typical intrazonal ecosystem dominated by Cynodon dactylon， Vitex negundo var cannabifolia， Cinnamomum camphora and so on， but it has its only zonal characteristic， such as C camphora， Celtis sinensis， Phyllostachys heterocycla etc are the dominant species of overstory， and this species are typical subtropical forest component species Additionally， affected by human activities， such as the nonpoint source pollutant input from agricultural production and bank duratect from urbanization， the riparian degraded in structure and function. Thus，we suggest that riparian areas may require reestablishment or restoration solution and different management strategies