| The research background and contentChongming Dongtan National Nature Reserve is one of the most important stopover sites for migratory waterbirds in Asian-Pacific Flyway, due to its unique geographical position in the Yangtze River Mouth and extensive salt marsh and mud tidal flat. However it is also one of the key regions which were enclosed by the construction of seawall, and the mud tidal flat after the reclamation was used for agricultural or industrial development, which altered the composition of the local plant community and the topography of the marsh and hence resulted in the dramatic decline of bird biodiversity. Since 2011, the local wetland management authority have taken the conservation measures to recover and optimize the wetland by creating two habitat pattern (rice-paddies, fish-ponds) in the coastal area. Due to the wetland restoration project, a part of natural reserve was transformed into artificial wetland. Many studies have shown that habitat pattern of rice-paddies, fish-ponds and other artificial wetland could attract birds, different habitat pattern played different role in attracting birds. However, none of these studies had not comparing the nature conservation artificial wetland under management with the unmanaged economical artificial wetlands. Therefore, this study mainly investigated the waterbird community structure in rice-paddies, fish-ponds artificial wetlands under different management models and critical habitat factors which affected the number of waterbirds. Then we summarized that which kind of the habitat patterns and management modes are suited to attract birds, made some suggestions for creating a suitable habitat of birds and restoring the function of the damaged wetland, especially for further promoting the restoring rice-paddies artificial wetland.Research methods and resultsThe study lasted from March,2013 to February,2014 that duration covered the flood tide period and the neap season period, the study respectively surveyed the birds and their habitats factor in different types of artificial wetlands. Bird surveys were conducted by the point count method and quadrat sampling method, sorted through the waterbirds data to calculate the number of species, the density, the diversity index and the evenness index.Finally SPSS 17.0 software for statistical analysis, we firstly tested whether the data accorded with normal distribution by non-parametric test (Kruskal-Wallis H), then analyzed the correlation between waterbird community characters (the number of species, the density, the diversity and evenness index) and the habitat factor (mean water level, anthropogenic disturbance, vegetation area percent,etc.) by using Spearman correlation analysis method, determined the key factors which affectd waterbird community, and concluded the waterbird habitat selection mode.We counted all the waterbirds to 9488 in different types of artificial wetlands in Chongming Dongtan during migratory season (the spring, autumn and winter) in 2013: totally 2357 waterbirds which subordinated in 6 orders 11 families and 45 species were counted in spring (March-May); totally 3843 waterbirds which subordinated in 5 orders 9 families and 36 species were counted in autumn (September-November); totally 3288 waterbirds which subordinated in 6 orders 7 families and 23 species were counted in winter (December-February). The restored fish-ponds artificial wetland kept the highest value in the number of the species in spring and winter, but the restoring rice-paddies artificial wetland was the highest in autumn. The number of species, density of the waterbirds in the restoring rice-paddies artificial wetland increased significantly after construction in spring. According to the Spearman correlation analysis method for habitat factors and waterbirds community characteristics, the analysis results are as follows:In spring:the number of waterbird species had highly positive significant correlation with bare muddy area percent, the number of habitat islands (P=0.002; P<0.001); Waterbird density had highly negative significant correlation with vegetation area percent and mean water level (P=0.003; P=0.006), but highly positive significant correlation with bare muddy area percent, the number of habitat islands (P<0.001; P<0.001); The diversity had highly positive significant correlation with bare muddy area percent and the number of habitat islands (P=0.005; P=0.001).In autumn:the number of waterbird species had highly positive significant correlation with plant height and bare muddy area percent (P<0.001; P<0.001); Waterbirds density had negative correlation with vegetation area percent and mean water level (P=0.107; P=0.080), but positive correlation with bare muddy area percent, water area percent and the number of habitat islands (P=0.189; P=0.297; P=0.454); The diversity had highly positive significant correlation with plant height (P<0.001).In winter:the number of waterbird species and the density had highly negative significant correlation with vegetation area percent (P<0.001; P<0.001), but highly positive significant correlation with water area percent (P<0.001; P<0.001), positive significant correlation with plant height (P=0.014; P=0.048), bare muddy area percent (P=0.001; P=0.023), the number of habitat island (P=0.021; P=0.045); The diversity had highly positive significant correlation with water area percent and the number of habitat islands (P<0.001; P=0.006).The number of species and quantity of the waterbirds were relatively high in the restored fish-ponds artificial wetlands, because the staff continuously took the follow-up measures to make the proportion of the combination between the vegetation area, water area and bare muddy area. Meanwhile, the staff used the tidal creek, depression and made the different gradient of water level by a set of into and the drainage system so as to attract all sorts of waterbirds.Restoring rice-paddies artificial wetland was repairing, it was under no management and human disturbance was large in the spring, No waterbird was observed. The full range of management were made to meet the waterfowl habitat requirements, including regulating water level, constructing channels and planting reeds so as to create a hidden environment in the surrounding in autumn. The number of species, the density and quantity of the waterbird was the highest in the restoring rice-paddies artificial wetland in autumn. However as no management, part of the water area was drought, the reeds were cut off surrounding. The number and quantity of waterbird species had conspicuously decreased.Economical rice-paddies artificial wetland and economical fish-ponds artificial wetland are all open and without the protection and management in this study. The economical fish-ponds management personnel set up the bird net, and used firecrackers to drive the birds in order to prevent birds hunting the fish, so the number of water birds declined dramatically. Economical rice-paddies artificial wetland made rice production as the goal, the vegetation density is too high, the only the deep-water canals and the pond around there, the quantity and the number of the waterbirds and the density were the smallest in autumn and winter. These two types of artificial wetlands were not used as suitable habitats for waterbirds, which not meet their habitat requirements. However, if effective managements were performed in such artificial wetlands to meet the waterbird habitat requirements, these two types of artificial wetlands can provide the best habitat for birds to survive.Management RecommendationsFish-ponds artificial wetland:1) propose to increase the bare muddy area and the number of the habitat islands so as to meet the different environmental factors’needs of different groups of birds; 2) reduce the area of which vegetation cover is too high, to provide more space for water birds’ activities, meanwhile consider that the vegetation can reduce the interference of the surrounding environment, planting appropriately is recommended in order to improve the isolation level between the water birds’mainly rest area and the surrounding environment.Coastal rice-paddies artificial wetland:1) plant high dense reed (Phragmites aust ralis) around the rice-paddies land to enhance the concealment; 2) paddy flooded peri od, maintain the water flooding status, increase bare muddy area and the number of ha bitat islands to meet the diverse habitat requirements of birds; 3) consider the require ments growing at different growth stages, control the water inlet and outlet system timely. |
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