The impact of natural succession process on waterbird community in a abandoned fishpond at Chongming Dongtan,China

In recently years,the artificial wetlands such as fishponds and rice pads have become the main habitats type for waterbird due to the decrease of natural wetland.Such phenomenon exists generally in Yangtze River coastline since the coast wetlands were reclaimed during last decade.However,part of artificial wetlands in these areas is being abandoned by local farmers in the reasons of labour cost increasing and aquatic product price decreasing comparatively.Some studies concluded that the abandonment of fishpond caused the deterioration of soil and water quality,and the decrease of benthic animals.However there are few studies about the influence of natural succession after the abandonment on waterbird community.Chongming Dongtan National Nature Reserve is one of the international wetland(Ramsar Site) for waterbird conservation,where we selected the abandoned fishpond as our research area to undertake the waterbird studies in 2007,2008 and 2011,aiming to the impact of rapid succession after abandonment on waterbird community structure,and raising relative recommendations on the further management of these abandoned fish ponds for local government. In a total of 12819 waterbirds of 59 species were observed in the three years,which belonged to 6 Orders and 12 Families.Among the total,in the year of 2007,pre-abandonment period,we counted 11001 waterbirds of 53 species,with the most abundance and richness value in our study years;in the year of 2008,the first year of fishponds abandoned period,we counted 1673 waterbirds of 22 species;in the year of 2011,the fourth year of fish ponds abandoned period,we only counted 145 waterbirds of 9 species;which indicated the waterbirds abundance and richness dropped dramatically after the fishpond was abandoned.The study results of variance analysis showed that the richness,abundance,species diversity,evenness and dominance of waterbird community all had highly significant differences among years(P10.01;P20.01;P30.01;P4=0.003;P50.01).The result of non-parametric test described that,the richness and abundance of different waterbird groups had highly significant differences among years. The findings of this study suggested that waterbird abundance and richness had the dropping trend,meanwhile water level and the percentage of water area decreased and vegetation coverage increased;the species diversity increased as well as the percentage of mudflat;the evenness had the same increasing trend as vegetation coverage,but opposite trend presented in the water level and the percentage of water area.The results also indicated that different waterbird groups such as waterfowls and shorebirds reacted variously to the different environment factors,for instance,the abundance and richness of shorebirds have risen rapidly in the first year of fish pond abandoned while the other groups decreased obviously. In order to raise the conservation value of these fishponds abandoned in this Ramsar Site,we recommend undertaking proper management measures in these areas to prevent the drought as well as increasing the heterogeneity of habitat for the waterbird conservation.