Based on historic topographic maps and field surveys, this paper mainly deals with the formation and evolution of the Jiuduansha Shoal and the North Passage and South Passage in the Changjiang Estuary. Jiuduansha Shoa...Based on historic topographic maps and field surveys, this paper mainly deals with the formation and evolution of the Jiuduansha Shoal and the North Passage and South Passage in the Changjiang Estuary. Jiuduansha Shoal originated from the partition of the south part of the Tongsha Shoal as the result of connection of a flood channel and an ebb channel. The embryo of the North Passage was a flood channel, and that of the South Passage was the lower reaches of the former South Channel. There were two basic kinds of change in erosion and accumulation since the formation of Jiuduansha Shoal: continuous change and periodic change. The former includes the broadening of the island area, accretion on the tidal marsh and tidal flat and downstream migration of the island. The latter includes cyclic erosion and accumulation on the two river channel banks of the island and the North and South Passages. The island and the two bifurcated river passages interacted on each other in erosion and accumulation changes. At present, the courses of the North Passage and the South Passage are relatively stable.展开更多
The evolution of the shoals and vegetation plays an important role in maintaining the stability of the river regime and the estuarine ecosystem. However, the interaction between the evolution of shoals and vegetation ...The evolution of the shoals and vegetation plays an important role in maintaining the stability of the river regime and the estuarine ecosystem. However, the interaction between the evolution of shoals and vegetation dynamic has rarely been reported. In this study, we determined the interaction between the shoal and vegetation evolution of Jiuduansha in the Changjiang River Estuary in the last 30 years. We did this through the collection and summarization of the existing data of the regional hydrological processes, wading engineering, and vegetation,and combined it with the analysis of nautical charts and remote sensing images. During the past 30 years, the expansion of the shoals within the 0 m isobath in Jiuduansha was obvious, with an increase of 176.5%, while the expansion of the shoals within the 5 m isobath was relatively slow. The regional hydrological characteristics in the Jiuduansha area changed dramatically, especially the sediment discharges. The area of vegetation in Jiuduansha increased from 9.1 km^2 in 1990 to 65.68 km^2 in 2015, while the variations in the different vegetation types were different. The best combination of environmental factors with a significant correlation on the shoals within the 0 m isobath is the area of Spartina alterniflora and Phragmites australis. The evolution of Jiuduansha shoals was significantly affected by the variations in hydrological characteristics. Meanwhile, on a long-term scale, the expansion of the shoals could promote the regional vegetation expansions due to the suitable elevation and environmental conditions it provides. The interaction between the shoal and vegetation evolution varied in the different vegetation types and different elevations. In the future, long-term monitoring and detailed data are needed to the systematical analysis of the interaction between the hydrological processes and the evolution of the shoal and vegetation.展开更多
The carrying capacity of food resources for migrating shorebirds was estimated at a stopover site in the Yangtze River Estuary during the two migratory seasons(spring and autumn).From March to May and September to Nov...The carrying capacity of food resources for migrating shorebirds was estimated at a stopover site in the Yangtze River Estuary during the two migratory seasons(spring and autumn).From March to May and September to November 2005,the macrobenthos resources of the Jiuduansha Wetland were investigated,and most of the macrobenthos species in the newlyformed shoal were found to be appropriate food for shorebirds.Biomass measurements showed that the total food resource was about 4541.20 kg AFDW(Ash-Free Dry Weight)in spring and about 2279.64 kg AFDW in autumn.Calculations were also done in the available habitats(intertidal bare mudflat and Scirpus×mariqueter/Scirpus triqueter zones)for the shorebirds.The food resources in the available areas were about 3429.03 kg AFDWin spring and about 1700.92 kgAFDWin autumn.Based on the classification(by lean weight,basic metabolic rate and body length)of the shorebird community,and using the energy depletion model,it was theorized that all of the food resources in the Jiuduansha Wetland could support about 3.5 million shorebirds during spring season and 1.75 million shorebirds during autumn season.The shorebird carrying capacities in terms of the available food were about 2.6 million and 1.3 million birds during the two respective migration seasons.Considering the effect of intake rate,the potential carrying capacity was about 0.13–0.26 million shorebirds in the study area.The main factor restricting use of the area by shorebirds was the scarcity of available habitats for roosting at high tide rather than availability of food supply.We recommend restoring some wading pools in the dense Phragmites australis and Spartina alterniflora zones for shorebirds to roost in,to improve shorebirds’utilization efficiency of the resources in the Jiuduansha Wetland.展开更多
As the loss of wild lands to satisfy traditional economic development has become a global environmental problem in recent decades, using ecosystem valuation to estimate the total economic value (TEV) of an ecosystem h...As the loss of wild lands to satisfy traditional economic development has become a global environmental problem in recent decades, using ecosystem valuation to estimate the total economic value (TEV) of an ecosystem has become popular. The main purpose of the ecosystem valuation is to strengthen the importance of ecosystems, and bring the ecosystem services into the traditional cost-benefit analyses of land use strategy. Some studies have illustrated that in remote areas, wilderness can produce more value if it is conserved, rather than converted to traditional agricultural or industrial uses. The same situation does not seem to exist in vigorous economic regions. Thus, a case study was conducted on the Jiuduansha Wetland in Shanghai using three approaches: the direct market valuation, the replacement valuation and the contingent valuation. The net present TEVs of three land use scenarios over one hundred years were evaluated. The results proved that simply based on ecosystem valuation, when compared with the other two scenarios of "conservation" and "selective use", "partial conversion into terrene (dry land)" of Jiuduansha might be the optimal scenario for the well-being of the people in Shanghai. Land price was identified as the most important factor. This situation is likely due to the scarcity of land available for traditional economic development in Shanghai. Thus, we speculated that the fate of the wilderness to "be destroyed" in vigorous economic regions could not be changed simply based on ecosystem valuation. However, the variety of interest by local residents in wilderness might enhance the TEVs of scenarios such as "conservation" and "selective use", and affect the valuation results. Since some important benefits of natural ecosystems remain unknown and others are underestimated, we suggested that any land use decisions regarding the Jiuduansha Wetland should be conservative and cautious as converting wetlands into terrene is an irreversible process.展开更多
文摘Based on historic topographic maps and field surveys, this paper mainly deals with the formation and evolution of the Jiuduansha Shoal and the North Passage and South Passage in the Changjiang Estuary. Jiuduansha Shoal originated from the partition of the south part of the Tongsha Shoal as the result of connection of a flood channel and an ebb channel. The embryo of the North Passage was a flood channel, and that of the South Passage was the lower reaches of the former South Channel. There were two basic kinds of change in erosion and accumulation since the formation of Jiuduansha Shoal: continuous change and periodic change. The former includes the broadening of the island area, accretion on the tidal marsh and tidal flat and downstream migration of the island. The latter includes cyclic erosion and accumulation on the two river channel banks of the island and the North and South Passages. The island and the two bifurcated river passages interacted on each other in erosion and accumulation changes. At present, the courses of the North Passage and the South Passage are relatively stable.
基金The funds from the Shanghai Science and Technology Committee under contract No.19DZ1203801the National Natural Science Foundation of China under contract No.41761144062。
文摘The evolution of the shoals and vegetation plays an important role in maintaining the stability of the river regime and the estuarine ecosystem. However, the interaction between the evolution of shoals and vegetation dynamic has rarely been reported. In this study, we determined the interaction between the shoal and vegetation evolution of Jiuduansha in the Changjiang River Estuary in the last 30 years. We did this through the collection and summarization of the existing data of the regional hydrological processes, wading engineering, and vegetation,and combined it with the analysis of nautical charts and remote sensing images. During the past 30 years, the expansion of the shoals within the 0 m isobath in Jiuduansha was obvious, with an increase of 176.5%, while the expansion of the shoals within the 5 m isobath was relatively slow. The regional hydrological characteristics in the Jiuduansha area changed dramatically, especially the sediment discharges. The area of vegetation in Jiuduansha increased from 9.1 km^2 in 1990 to 65.68 km^2 in 2015, while the variations in the different vegetation types were different. The best combination of environmental factors with a significant correlation on the shoals within the 0 m isobath is the area of Spartina alterniflora and Phragmites australis. The evolution of Jiuduansha shoals was significantly affected by the variations in hydrological characteristics. Meanwhile, on a long-term scale, the expansion of the shoals could promote the regional vegetation expansions due to the suitable elevation and environmental conditions it provides. The interaction between the shoal and vegetation evolution varied in the different vegetation types and different elevations. In the future, long-term monitoring and detailed data are needed to the systematical analysis of the interaction between the hydrological processes and the evolution of the shoal and vegetation.
基金This study was sponsored by the National Technology Support Program(No.2006BAC01A14)Shanghai Technology&Science Administration Key Project(No.06DZ12303)Shanghai Educational Development Foundation.
文摘The carrying capacity of food resources for migrating shorebirds was estimated at a stopover site in the Yangtze River Estuary during the two migratory seasons(spring and autumn).From March to May and September to November 2005,the macrobenthos resources of the Jiuduansha Wetland were investigated,and most of the macrobenthos species in the newlyformed shoal were found to be appropriate food for shorebirds.Biomass measurements showed that the total food resource was about 4541.20 kg AFDW(Ash-Free Dry Weight)in spring and about 2279.64 kg AFDW in autumn.Calculations were also done in the available habitats(intertidal bare mudflat and Scirpus×mariqueter/Scirpus triqueter zones)for the shorebirds.The food resources in the available areas were about 3429.03 kg AFDWin spring and about 1700.92 kgAFDWin autumn.Based on the classification(by lean weight,basic metabolic rate and body length)of the shorebird community,and using the energy depletion model,it was theorized that all of the food resources in the Jiuduansha Wetland could support about 3.5 million shorebirds during spring season and 1.75 million shorebirds during autumn season.The shorebird carrying capacities in terms of the available food were about 2.6 million and 1.3 million birds during the two respective migration seasons.Considering the effect of intake rate,the potential carrying capacity was about 0.13–0.26 million shorebirds in the study area.The main factor restricting use of the area by shorebirds was the scarcity of available habitats for roosting at high tide rather than availability of food supply.We recommend restoring some wading pools in the dense Phragmites australis and Spartina alterniflora zones for shorebirds to roost in,to improve shorebirds’utilization efficiency of the resources in the Jiuduansha Wetland.
文摘As the loss of wild lands to satisfy traditional economic development has become a global environmental problem in recent decades, using ecosystem valuation to estimate the total economic value (TEV) of an ecosystem has become popular. The main purpose of the ecosystem valuation is to strengthen the importance of ecosystems, and bring the ecosystem services into the traditional cost-benefit analyses of land use strategy. Some studies have illustrated that in remote areas, wilderness can produce more value if it is conserved, rather than converted to traditional agricultural or industrial uses. The same situation does not seem to exist in vigorous economic regions. Thus, a case study was conducted on the Jiuduansha Wetland in Shanghai using three approaches: the direct market valuation, the replacement valuation and the contingent valuation. The net present TEVs of three land use scenarios over one hundred years were evaluated. The results proved that simply based on ecosystem valuation, when compared with the other two scenarios of "conservation" and "selective use", "partial conversion into terrene (dry land)" of Jiuduansha might be the optimal scenario for the well-being of the people in Shanghai. Land price was identified as the most important factor. This situation is likely due to the scarcity of land available for traditional economic development in Shanghai. Thus, we speculated that the fate of the wilderness to "be destroyed" in vigorous economic regions could not be changed simply based on ecosystem valuation. However, the variety of interest by local residents in wilderness might enhance the TEVs of scenarios such as "conservation" and "selective use", and affect the valuation results. Since some important benefits of natural ecosystems remain unknown and others are underestimated, we suggested that any land use decisions regarding the Jiuduansha Wetland should be conservative and cautious as converting wetlands into terrene is an irreversible process.
