| The Yangtze River Estuary is one of the50most ecologically sensitive regions in the world. The Chongming Dongtan wetlands, one of the most important wetland ecosystems in the lower reaches of the Yangtze River. In2002, the area was designated as a Ramsar Site. The annual use of coastal wetlands in Chongming Dongtan by thousands of migratory waterbirds indicates that these wetlands are important stopover and wintering sites for migratory birds in the East Asia-Pacific Flyway. In the last decades, the Chongming Dongtan wetlands seriously suffered loss, deterioration, and fragmentation caused by frequent large-scale reclamation of intertidal areas and invasion by Spartina. In recent years, artificial wetlands have been restored or created to compensate for wetland loss and deterioration. To understand the relationship between waterbird population changes and their corresponding habitat changes, changes in waterbird potential suitable habitats and responses of waterbird community to wetland restoration strategies in the Chongming Dongtan Wetlands, China, this study aims to1) analyze the relationship between waterbird population changes and their corresponding habitat changes,2) evaluate and simulate changes in the area and spatial pattern of waterbird potential suitable habitats based on the CA-Markov model,3) determine what artificial wetlands will host more waterbirds. The major results of present study are summarized as follows:1) Changes in waterbird populations in relation to their habitat changes are of great concern in the Chongming Dongtan wetlands, one of the most important stopovers for migrating birds in the East Asian-Australasian Flyway. We analyzed the relationship of the changes in the dominant waterbird populations (Charadriidae, Anatidae, Ardeidae, and Laridae) with the changes in their corresponding habitats from2006to2012. Significant differences in waterbird individuals per survey were observed between natural and artificial wetlands, as well as among seasons. Results of time-series analysis of waterbird individuals per survey as well as their habitats indicated that individuals per survey of four dominant waterbird all showed decline trens from2006to2012. Scirpus, mudflat, deepwater and artificial wetlands showed sharply decline trends. Phragmites and Spartina, however, showed drastically increasing trends. In natural wetlands, the changes in waterbird individuals per survey were positively correlated with the changes in the Scirpus mariqueter (hereafter Scirpus), the deepwater (except Charadriidae in spring and autumn), and the mudflat and shallow water (hereafter mudflats) habitats, but inversely correlated with the changes in the Phragmites australis (hereafter Phragmites) and the Spartina alterniflora (hereafter Spartina) habitats. In artificial wetlands, the changes in waterbird individuals per survey (Anatidae in winter) were positively correlated with the changes in aquaculture ponds. However, such correlations were not reached significant level. Natural wetlands and aquaculture ponds are important to migratory waterbirds during the peak of migration and wintering, and may be especially important to Anatidae species during winter as well as other swimming birds in all seasons. Consequently, changes in waterbird populations are correlated with changes in natural and artificial wetlands in the Chongming Dongtan wetlands. Our results promote the development of wetland management strategies for protecting migratory waterbirds in the coastal area of the Yangtze River.2) Cellular Automata (CA) and Markov models were previously used separately or in pairs to simulated land use change. This study applied an integrated CA-Markov model to analyze spatiotemporal changes in waterbird potential suitable habitats. Results showed that the model was useful for waterbird potential suitable habitat change simulation. Area change simulation projected a continuing downward trend in deepwater habitat, Scirpus mariqueter (hereafter Scirpus) and mudflat habitats, as well as a substantially upward trend in Phragmites australis (hereafter Phragmites) and Spartina alterniflora (hereafter Spartina) habitats. Deep water habitats were mainly transferred to Scirpus and mudflat habitats; Scirpus and mudflat habitats were mainly transferred from deep water habitats, while transferred to Phragmites and Spartina; Phragmites and Spartina created their areas by replacing Scirpus and mudflat habitats. Spatial distribution simulation indicated that waterbird potential suitable habitats(Scirpus and mudflat habitats) would expand to deep water habitat, but replace by Phragmites and Spartina habitats; Meanwhile, Phragmites and Spartina habitats would exhibit the concentrated spatial distribution patterns and became the most dominant vegetation by substantially replacing Scirpus and mudflat habitats. As a consequence, if the current trends were not modified with holistic effective management strategies, wetlands would seriously deteriorate. The study may be helpful for local governments to develop wetland management policies to protect the coastal wetlands.3) The Chongming Dongtan wetlands were subjected to loss, deterioration, and fragmentation of coastal wetlands. In recent years, artificial wetlands have been constructed to protect waterbirds in this region. This paper aims to determine whether constructed artificial wetlands used equally by waterbirds and find out the preferred habitats of waterbirds, so as to determine what artificial wetland configuration would host more waterbirds. We quantified the waterbird community composition at three artificial wetlands (sites A, B and C) and on one natural coastal wetland (site D), which served as a reference site, from September2011to May2012in the Chongming Dongtan wetlands. The Shannon-Wiener diversity index was calculated to describe habitat diversity in the four study sites. Results showed that significant differences in habitat heterogeneity and species group diversity, richness, and waterbird density were observed in the sites, but a significant difference among three seasons was observed only in the waterbird density. Significant interactions between site and season were noted for species group diversity, richness, and waterbird density. Then we analyzed the utilization of restored wetlands by four ecological waterbird guilds (shorebirds, diving birds, dabbling ducks and herons), as well as their preferences of habitat types. Results showed that shorebirds was abundant in spring (preferred site C&D) and autumn (preferred site C); diving birds and dabbling ducks were both abundant in winter, while diving birds preferred site B and followed by site C, but dabbling ducks preferred site C; herons was abundant in autumn (preferred site C) and winter (preferred site B and followed by site C). Each waterbird guilds exhibited unique and complex habitat preferences. Specifically, shorebirds preferred mudflats and shallow water, but were most abundant on mudflats. Diving birds selected open water as the unique habitat. Most dabbling ducks preferred open water, however some ducks were observed on Scirpus mariqueter (hereafter Scirpus) habitat. Herons exhibited the widest range of habitat preferences (shallow water, mudflats and Scirpus). In conclusion, the artificial wetlands served as a suitable habitat for waterbirds to some extent, although were not used equally by waterbirds. Multi-functional artificial wetlands could be constructed by incorporating diverse habitats to attract a greater abundance of waterbirds in the East Asia-Pacific Flyway to forage and roost in the coastal wetlands of Yangtze River Estuary. |
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