Relationship between Herbaceous Communities Succession and Hydrological Regimes in Napahai Wetland

Through dividing Napahai wetland of Yunnan,China into hundreds of equal-size grids,quadrat sampling was adopted to investigate herbaceous communities and species in each accessible grid.Detrended Correspondence Analysis(DCA) ordination was used to reveal the community succession phases and the major driving factor.Four species diversity indices were calculated for all community samples.Then we explored the impacts of the variation of the major driving factor indicated by DCA AX1 upon community species diversity.The study recorded 130 species,grouped into 88 genera and 36 families.Within the wetland,the mixed hygrophyte-mesophytes are the most widely distributed communities,then the mesophytes,the secondary communities on severely damaged habitats,and the hydrophytes,which are the four succession stages.DCA ordination showed the gradient variation of hydrological regime is the primary factor to determine the community succession stages of Napahai wetland; while,freerange pig directly caused the severe damage of wetland habitats and then the secondary community succession.Present hydrological regime of and free-range animal husbandry within the wetland will lead to the increase of hygrophyte and mesophyte scpecies,as well as some companion species related to disturbances,which indicates higher potential risk of community degradation.Regulating hydrological regime to increase flooding area and frequency,and adopting enclosure breeding to weak livestock(especially the pigs) disturbance are the basic measures to promote community restoration of Napahai wetland.